U.S. Air Force Research Lab Summer Faculty Fellowship Program

U.S. Air Force Research Lab Summer Faculty Fellowship Program

U.S. Air Force Research Lab Summer Faculty Fellowship Program

AFRL/RV (Kirtland Air Force Base, New Mexico )

SF.40.21.B10062: Advanced Space Power

Walters, Robert - 505-967-9118

The Advanced Space Power (ASP) program is focused on developing and demonstrating advanced space power system technologies for USAF space assets, ranging from dedicated, heritage systems to contributing, agile systems. Through in-house research and a managed portfolio of contracts, ASP meets the growing power demands needed to provide enhanced capability in signal processing, sensing, autonomy, and space control.

SF.40.21.B10061: Resilience-Aware Human-on-the Loop Conformance Framework for Positioning, Navigation, and Timing

Pham, Khanh - 505-846-4823

With the automation and multi-level resilience of prevent, respond, and recovery functions involved in Positioning, Navigation, and Timing (PNT) equipment, human presence is almost inevitable in such systems. The vast majority of PNT services mandate the presence of end users being with supervisory roles (Human-on-the-Loop), such as resilience level settings, risk tolerances, budgets, dual-purpose civil and military application criticality and interfering in situations unfamiliar to the autonomous PNT equipment. Hence, it is vital to understand how this presence affect the application performance requirements of accuracy, availability, integrity, continuity, and/or coverage and expected behaviors in resilient PNT equipment at design phase. Moreover, this understanding serves a radical change in the design paradigm: can we design autonomous PNT equipment that utilize human presence in improving the provided resilience guarantees or aiding with situations of higher degrees of uncertainty?
The research topic is focusing on exploring the answer to this question for resilience future proof and broadly applicable across civil and military PNT sources; e.g., GNSS-dependent time and frequency sources and receivers. Specific activities may investigate the human role in resilience and/or security guarantees when PNT equipment are susceptible to jamming and spoofing attacks. The technical challenge is threefold: i) Understanding human behavior; ii) Developing conformance frameworks for PNT resilience agnostic to all critical infrastructure sectors, all applications, all PNT sources or services, and all threats; and iii) Synthesizing expected behaviors and outcomes for resilient PNT user equipment.

SF.40.21.B10060: Integrated Structural Systems for Spacecraft

Urioste, Benjamin - 505-846-1539

Our research team is focused on developing new and novel technologies for spacecraft in the area of spacecraft structures, thermal control, and power systems. We seek new ideas to revolutionize the future of spacecraft design. New approaches to power spacecraft and control thermal waste heat are critical for future satellite designs. Of particular interest is research focused on advancing state of the art in deployable structures for spacecraft with an emphasis on use of novel materials. As the demand for robust power and sensing solutions grows so does the need for more efficiently stowed and deployed structures. Additionally, research on meta-materials to enable to remote sensing paradigms is of interest.

SF.40.21.B10037: Distributed Satellite Autonomous Systems

Phillips, Sean - 505-853-8531

This project seeks to develop novel methods, techniques and algorithms for challenging spacecraft guidance, navigation control and autonomy (GNC) problems. Specifically, new approaches are being developed for (a) cooperative autonomous spacecraft relative-motion guidance and navigation approached for rendezvous and proximity operations, (b) unique distributed task allocation algorithms for optimal or near-optimal task assignment and control, (c) robust and resilient networked communications and data distribution algorithms, (d) verification and validation techniques for nonlinear/multi-mode satellite control algorithms, and (e) coordinated vision-based feature reconstruction, pose estimation and/or relative navigation. Research proposals that address one or more of these topics from a theoretical or experimental perspective are of interest. This research can make use of the experimental facilities at AFRL/RV, including a cooperative multi-agent systems laboratory. Keywords: hybrid systems; verification and validation; estimation; optimization; guidance; navigation; control theory; satellite systems; spacecraft; image processing; SLAM; autonomous multi-spacecraft; coordinated control; resilient communications systems; autonomy; learning. C. Petersen, S. Phillips, K. Hobbs, and K. Lang. “Challenge Problem: Assured Satellite Proximity Operations”. Proc. AAS Spaceflight Mechanics. 2021; A. Zaman, A. Soderlund, C. Petersen, and S. Phillips. “Autonomous Satellite Rendezvous and Proximity Operations via Model Predictive Control Methods”. In Proc. AAS Spaceflight Mechanics, 2021; F. Parra and S. Phillips. “A Case Study on Auction-Based Task Allocation Algorithms in Multi-Satellite Systems”. Proc. AIAA Scitech 2021 Forum. 2021; S. Phillips, C. Petersen, R. Fierro. “Robust, Resilient and Energy Efficient Satellite Formation Control,” Intelligent Control and Smart Energy Management: Renewable Resources and Transportation. 2021; C. Petersen, S. Phillips, D. Hustig-Schultz, R. G. Sanfelice, “Towards Hybrid Model Predictive Control for Computationally Aware Satellite Applications,” Proc. Workshop on Computation-Aware Algorithmic Design for CPS, 2021; J. M. Brewer, P. Tsiotras, K. Lang, S. Phillips, “Falsification-based Verification for Multi-Mode Spacecraft Attitude Control Systems,” In Proc. of ACC, 2021.

SF.40.21.B0008: Network Function Synthesis in Software-Defined Satellite Networks

Pham, Khanh - 505-846-4823

While potential benefits of software-defined networking (SDN) for flexible network management and network function virtualization (NFV) for virtual functions on dedicated hardware have been extensively investigated in terrestrial wireless networks, their applications to satellite networks has however not been adequately explored for flexible function management. In this topic, SDN and NFV are being advocated for the realization of different types of incumbent tasks; e.g., data communications, sensor observations, etc. while subject to network topology dynamisms, inter-satellite link availability, etc. Future development efforts in software-defined frameworks for space and terrestrial satellite communications to achieve flexible management should consider a vision of virtualized resource management systems that are supported by adaptive synthesis and orchestration of virtualized network functions (VNFs) on each satellite and subject to operational constraints on flows, network resources, VNFs, and connectivity between flows and VNFs. Nevertheless, sustainable impact assessments of NFV degrees to the overall network performance are in needs for potential enhancements in task completion and network resource utilization versus the number of VNF enabled satellites with different computing and communication capacities.

SF.40.21.B0007: Enterprise Management & Control of Military and Commercial Satellite Communication Networks

Pham, Khanh - 505-846-4823

Albeit loose interactions between military and commercial satellite communication (MILSATCOM and COMSATCOM) communities, the integration of military and commercial SATCOM networks can be a cornerstone to the realization of seamless SATCOM services. In this topic, flexible capabilities and requirements from Software-Defined Networking (SDN) Networking Coding (NC) foundations are leveraged to potentially enable enterprise management and control reference architectures in realizing appropriate management and control planes overlay on the end-to-end SATCOM capability, within which diverse arrays of SATCOM access networks and terminals could be brought into the SATCOM enterprise with efficient use of time-bandwidth resource and satisfaction of communication reliability. Primary interests are in integrated systematic approaches, requirements and guidelines for SDN-based overlay and data forwarding protocols that reside at network operation centers to interface with user planes (including, MILSATCOM and COMSATCOM gateways together with corresponding SDN switches or routers; satellite transponders, ground transport infrastructures, etc.). State-of-the-art knowledge graphs and deep learning frameworks could be utilized for autonomous diagnostics and prognostics to anticipate for weather impairments, feeder link outage events, gateway buffer occupancies, and satellite link condition measurements. With respect to traffic flow association and re-allocation subject to service level agreements and pooled satellite resources together with maximum acceptable delay, minimum required throughput, and maximum tolerated losses, NC seemingly appears to be a promising approach to the much needed development of innovative handover and load balancing strategies required to distribute multi-class traffic flows throughout the available gateways and to re-allocate traffic flows in case of gateway link outages.

SF.40.21.B0006: Nontraditional and Resilient Satellite Navigation and Timing

Pham, Khanh - 505-846-4823

Part of the core dominance in space resilience is the ability to effectively position, navigate and synchronize all space assets in contested, degraded and operationally limited (CDO) environments. Future resilient satellite navigation and timing (PNT) is expected to be rapidly tailorable to execute in any geographic region, orbital regime, and adaptable to support the full range of missions. The objective of this topic is to identify innovative solutions, nontraditional approaches, and out-of-the-box concepts of operations that can be feasibly leveraged for applicability in CDO environments. More specifically, adaptive multi-flow carrier aggregation (multi-flow CA) and advanced link layer structures are envisioned to enable a persistent PNT capability of rapidly and securely connecting geographically separated all-domain sensors, actuators and end-effectors that are being served simultaneously from geographically separated locations using distinct component GPS frequency carriers. Also of interests are innovative packet scheduling and responsive load balancing strategies allocating incoming PNT packets based on link capacities and fill rates of the aggregated carriers among multiple serving PNT platforms from different tiers of missions. Expected metrics and attributes may include queuing delay, packet loss probability, out-of-order delivery, and spectral usage. Last but not least, PNT system accuracy and integrity are sought during CDO operations, where scientific foundations and design principles are of concerns to networking and fusion of line-of-sight and non-line-of sight radio frequency platforms inside and outside GPS denied areas, in order to diffuse the fused PNT results to all-domain platforms in the PNT network and/or theater operations. Some research efforts, including social learning, belief propagation, spanning trees, optimal edge selection, etc. may have relevant benefits in impacting PNT system accuracy, complexity, fault-tolerance, and real-time convergence.

SF.40.21.B0005: Network Tomography Inference for Multi-Domain Operations

Pham, Khanh - 505-846-4823

In the context of joint warfighting forces, future all-domain operations are envisioned as an enterprise-level management system that is consisted of functions such as critical surveillance, tactical edge communications, processing, networking, and battle management command and control capabilities. More specifically, timely and actionable information need to traverse through trusted networks that enable warfighters to focus on decisions. Essentially, network topology awareness is a critical part of network states that support a variety of network management tasks such as service placement, routing, overlay construction and load balancing. This research topic is looking for solutions, requirements, and feasibility studies to infer internal topology with minimal ambiguity for an all-domain network using end-to-end measurements collected from a subset of local devices and network management protocols owned and managed by different network access providers. In addition, recognizing the importance of incumbent networks potentially employing network function virtualization, information as a service may likely need to traverse a chain of virtualized network functions and segments before reaching to multiple destinations with certain measures of reliability and assurance in contested environments. Topology tomography and topology inference under waypoint based routings are some typical research efforts in order to impose the constraint that each path must traverse a predetermined sequence of waypoints, weighted topology consistent with all the end-to-end measurements taken from an arbitrary underlying topology, and thus, improving topology inference accuracy.

SF.40.21.B0004: Responsive Multi-Beam Arrangements for Operational Flexibility and Superior Coverage in High Throughput Satellites

Pham, Khanh - 505-846-4823

In recent years, high throughput satellites (HTSs) are utilizing Ku and Ka bands with many spot beams and high frequency and polarization reuses to provide high user throughput in diverse communication applications. With regards of wide spread of 5G in Ku and Ka bands, it is therefore necessary to realize efficient allocation of limited communication resources to the coverage area anywhere within the field of regard of an HTS by allowing flexible adjustments of power, frequency, or time resources between multi-spot beams. When an HTS adjusts the transmission power and beam directivity of each spot beam in situations where operational flexibility, exquisite coverage, and guaranteed traffic demands are unique, irregular and not uniform, there are however, no mathematical foundations for power resource allocation with energy efficiency, in which the positions of multi-spot beams are considered explicitly. In this topic, better understanding of potential relationships between the positions of multi-spot beams and the overall HTS throughput; e.g., distances between spot beams in the same frequency band and those in different frequency bands in relation to the overall system throughput, is essential. In addition, practical constructs and design principles are sought for effective and responsive multi-spot beam arrangements with consideration for inter-beam interference mitigation that would break the regularity traditions in beam arrangements and further enable effective power resource allocation to enhance the throughput of an HTS.

SF.40.21.B0003: Machine Learning Ready Sensing for Resilient Satellite Navigation

Pham, Khanh - 505-846-4823

It is now more important than ever for autonomous space assets be equipped with on-board positioning, navigation and timing (PNT) that are resilient in operationally challenged and/or degraded GPS environments. In this topic, both machine learning and its practical fronts of non-linear, non-stationary based signal decomposition approaches are the cornerstones for the realization of dynamic sensing and local edge processing, where feature extractions are adapted in responding to ubiquitous kinds of signals, including but not limited to radio frequency (RF) and non-RF signals of opportunity. Also relevant are feature construction frameworks with appropriate support of data fusion operations that are beneficial to representing natural characteristics of the signals of interest such as frequency band variations, statistic time-frequency variations, and correlations in sparse feature domain, etc. despite of the inherent challenges in different sizes and formats of signal features. Breakthroughs in deep learning based signal classification and adaptive feature reconstructions are foundational to reconfiguring PNT payloads and software defined radios for the development of a scalable, open architecture, and sensing enterprise that potentially enables timely and responsive detection of adversary or anomalous activities with respect to overall PNT performance and capabilities. Testing and evaluation of feature extraction and classification performance are essential when facing the challenge of dynamic ranges of signal-to-noise-ratios.

SF.40.21.B0002: Enterprise Space Data Transport Incorporating 5G

Pham, Khanh - 505-846-4823

An ever growing demand for enterprise space data transport has recently started in providing space-layered elements for joint all-domain command and control; ubiquitous communication; and positioning, navigation, and timing to the terrestrial warfighter and throughout the cislunar sphere. New standards and technologies, such as 5G that are expected to meet large throughput increase, seamless connectivity, reliability, and connection density, have become important to the fulfillment of the significantly demanding requirements in flexible interconnections of heterogeneous terrestrial and space assets, timely data dissemination in contested, degraded, and operationally-limited environments as well as to support novel 5G satellite market segments. In this context, this research topic is to focus on potential cross-cutting areas required to integrate 5G terrestrial networks with satellite networks. Such a realization of the enterprise space data transport capability across all mission areas can only be achieved by means of a radical shift in the way both the satellite access and the 5G terrestrial core networks are designed. For instance, typical satellite channel impairments, large path losses, delays, and Doppler shifts pose sever challenges to the realization of a 5G-based space data transport network. Of particular interests include, but not limited to: i) the impact of satellite channel characteristics on both physical and medium access control layers in terms of sub-carrier spacing, frame duration, etc. as well as user random access and timing protocols for enhanced mobile broadband and narrowband-Internet of Thing applications; ii) types of user link access by 5G user equipment interfacing with satellite networks; i.e., next-generation nodeB, terrestrial core networks air-interfacing with satellite transponders, satellite gateways, etc.; and iii) effective placements and selections of satellite gateways and terrestrial 5G core network management & control entities potentially capable of optimizing end-to-end network performance; e.g., latency, reliability, etc. pertaining to the enterprise space data transport capability.

SF.40.21.B0001: 5G for Resilient and Agile Positioning, Navigation, and Timing Transport

Pham, Khanh - 505-846-4823

Research concepts and feasibility studies are of particular interest to develop requirements for resilient and agile positioning, Navigation, and Timing (PNT) transport terrestrially, in space, and in space-to-ground-link systems by leveraging rapidly emerging 5G technologies. Also relevances are potential system cost reduction trade-offs pertaining to any or all the following areas; e.g., 1) Control Segment - global network of ground facilities that track PNT platforms, monitor their transmissions, perform analyses, and send commands and data to them; 2) User Segment - receivers/processors and antennas which receive PNT signals; and 3) Space Segment - constellations of satellites transmitting radio signals to users. Example aspects of 5G applied to PNT augmentations and/or PNT-alternative systems may include, but not limited to: i) What improvements would 5G massive Multiple-Input and Multiple-Output provide for PNT applications and in Electronic Warfare-contested Radio Frequency domains?; ii) What are potential opportunities for Multi-tenant Edge Computing by 5G in ground support networks for a Control Segment? iii) To what degrees could 5G technologies for Radio Access Network slicing and orchestration Observe-Orient-Decide-Act Loops be adapted to connect an User Segment through terrestrial networks to a Control Segment and then to a Space Segment?; and iv) What are 5G and emerging 6G cybersecurity technologies applicable to protecting such PNT systems from unauthorized access and manipulation?

SF.40.20.B0007: Application of Low Cost Optical and Near-Infrared Telescopes, Commodity Sensors, with Innovative Analysis using High Speed Computing and State of the Art Algorithms to Remote Sensing of the Properties of Low Earth Orbit Objects

Pereira, Wellesley - 505-853-3624

Our group`s research centers on innovative techniques for imaging and analyzing unique signals from ground, space, and airborne sensors. These signals span the hyperspectral, hypertemporal and spatial domains, and are utilized in a growing number of applications in intelligence, surveillance and reconnaissance. Because of the very steep dependency of cost on a telescope`s diameter, almost all ground-based Space Situational Awareness (SSA) in the
critical EO/IR regime is carried out with apertures that are too small to resolve important spatial structure on Resident Space Objects (RSO). This is true even for objects at relatively close range in Low Earth Orbit (LEO) where the limit of resolution without an expensive adaptive optics system on a large telescope is about 2 m as a consequence of atmospheric turbulence. We propose to utilize existing hardware -- a 10-inch portable telescope, and optionally 0.5
and 0.6 meter observatory telescopes -- with fast efficient high dynamic range photometry using CCD, CMOS, and InGaAs sensors and broadband filters to collect temporal and spectral data on known Resident Space Objects. Their temporal signatures reveal rotation, internal motions, and changes of state, and their spectral components and temporal variability may indicate design, function, and thermal mass. Precise active tracking with pixel-level precision will yield photon-noise limited signals, while predictive tracking of a known path over a wide field with static pointing may enable correlation of data and turn spatial into temporal information. Techniques in use now on images from the NASA TESS satellite may be applied, leveraging the computational gains of cluster and GPU computing for the detection and analysis of RSOs. With known RSOs as training sets, we would identify pathways to yield their shape, size, spatial configuration, dynamics, and potentially thermal mass. We will explore using artificial intelligence to extract information from the acquired signals, as this has the potential both to automate, and to detect new phenomena.

SF.40.20.B0006: Wave-Particle Interactions in the Magnetosphere

McCollough, James Parker - (505) 846-3197

The effects of in situ injection of high-power VLF radio waves on particle populations in the magnetosphere are not known, and modeling efforts are poorly constrained [1]. To better constrain the problem, the Air Force Research Laboratory will soon launch its Demonstration and Science Experiments (DSX) mission to investigate wave-particle interactions and the particle and space environment in medium Earth orbit (MEO).
The payload includes the Wave-Particle Interactions (WPIx) instrument suite, which includes VLF transmitters, receivers, and the Loss Cone Imager (LCI) particle detector [3]. WPIx will be employed to investigate VLF transmission, propagation, and interaction with trapped particles in a controlled manner. WPIx will also be used to observe the natural wave population and explore the basic physics of an antenna in a plasma.
The Space Weather Experiment (SWx) suite includes five particle instruments to survey the MEO electron and proton environment across a wide energy spectrum. Many of these instruments include pitch-angle resolution to allow thorough characterization of relevant populations. The SWx suite will provide context in which to interpret WPIx observations, in particular wave power lost to local heating. In addition, the orbit of DSX will allow study of the dynamics of the particle population in the slot region. SWx will provide data to augment and develop dynamical models of Earth`s natural radiation belt [2].
This project will support science exploitation of DSX data to better understand the effects of VLF waves on the natural particle population in the magnetosphere, and will encompass data reduction and analysis, modeling, and theoretical work to provide science closure on the question of direct injection of VLF radio waves into the magnetosphere.
1. Albert, Jay (2017), Quasi-linear diffusion coefficients for highly oblique whistler mode waves, J. Geophys. Res., 122(5), 5339-5354, doi:10.1002/2017JA024124.
2. Coleman, Timothy, James P. McCollough, Shawn L. Young, and E. Joshua Rigler (2018), Operational Nowcasting of Electron Flux Levels in the Outer Zone of Earth`s Radiation Belt, Space Weather, 16, 501-508, doi:10.1029/2017SW001788.
3. Parker, Charles W., Theodore A. Fritz, and Doug B. Carssow (2016), The Loss Cone Imager, Nucl. Instr. Meth. Phys. Res. A, 808, 11-20, doi:10.1016/j.nima.2015.11.010.
Keywords:plasma waves; radiation belts; space weather; VLF; ELF; ULF; whistler waves; relativistic electrons; EMIC waves; energetic charged particles

SF.40.20.B0005: Space Experiments, Space Sensor Development, Space Systems, DOD Relevant Astronomy

White, Stephen - (505) 853-6158

Research areas include conducting experiments from space sensors and from the ground, space situational awareness, space sensor development & instrumentation, space imaging, polarimetry of RSOs, space weather effects, spacecraft signature detection, development of space- and ground-based sensors, artificial intelligence, data mining, multidisciplinary instrumentation, and engineering. We develop space- and ground-based sensors; apply numerical, modeling, and artificial intelligence to understand data; develop models of space systems and their performance; use intelligent systems to understand space; and use space situational awareness to mitigate the impact on DOD systems. Our goals are to (1) design, develop, construct, test, and deploy instrumentation for ground- and space-based measurements using high spatial, temporal and spectral resolution by optical imaging, spectroscopy, and spectropolarimetry; (2) develop spectroscopic radiative transfer; and (3) develop and test physics and numerical-based models.
References
Ferguson D, White S, Rast R, Balasubramaniam KS: Ground-Based Surveillance Campaign to Detect Global Positioning System Arcing: First Preliminary Results. Journal of Spacecraft & Rockets, 2017 Accepted,
https://arc.aiaa.org/doi/10.2514/1.A33724
Balasubramaniam KS, Henry TW: Sunspot Numbers from ISOON: A Ten-Year Data Analysis. Solar Physics 291(9-10): 3123-3138, 2016. https://arxiv.org/abs/1602.07741
Winter LM, Balasubramaniam KS: Using the maximum X-ray flux ratio and X-ray background to predict solar flare class. Space Weather 13(5): 286-297, 2015. https://arxiv.org/abs/1504.00294
Kirk MS, Balasubramanaim KS, et al: Qualities of Sequential Chromospheric Brightenings Observed in Halpha and UV Images. The Astrophysical Journal 796: 78, 2014
Balasubramaniam KS, Pevtsov AA: Ground-based synoptic instrumentation for solar observations. SPIE Volume 8148, id. 814809, 2011
Keywords:Space Experiments from space-based and ground-based platforms; Space Systems; Space sensors; Sensor Calibration and Integration; Space situational awareness; Space weather; Optics and instrumentation; Magnetohydrodynamics; Imaging; Polarimetry; Spectroscopy; Radiative transfer; Observations; Artificial intelligence; Data processing;

SF.40.20.B0004: AFRL Chemical Processes in the Space Environment

Prince, Ben - (505) 846-7255

We use experimental and theoretical tools to examine a broad range of hyperthermal processes including 1) interactions between atmospheric species and surfaces, 2) chemical and electric thruster plumes with atmospheric species, 3) interactions occuring in the plumes of next-generation propulsion technologies and 4) fundamental ion-neutral collision processes. Typical experimental techniques include guided-ion beam tandem mass spectrometry, quadrupole and time-of-flight mass spectrometry, optical emission spectroscopy/spectrometry, laser-induced fluorescence detection and measurement of ion conversion efficiency for atmospheric sensors. The laboratory houses 5 different high vacuum experimental systems and has access to high-performance computing resouces for theoretical treatment of experimental results. Areas of current particular interest are experimentation relevant to the re-entry vehicle environment where electronic, vibrational and rotational excited states are common and experimental data is sparse, development and understanding of the microphysics associated with ionic liquid propelled electrospray thruster technology, quantification of processes leading to thruster signatures of in-space propulsion systems, and fundamental charge-exchange physics with an emphasis on quantification of scattering angles, energy transfer, and branching ratios. Also of general interest are: methods to determine and predict performance of different ionic liquids in an electrospray thruster application including providing insights into potential spacecraft contamination, evaluation of sensor materials for real-time orbital drag measurements, and alternative approaches to addressing space situational awareness needs. We use the results of the fundamental work performed in the laboratory to improve on and guide development of systems of interest to the Air Force and the DoD at large.
Keywords:Electric propulsion; Charge-transfer; Hyperthermal physics; Hypersonic re-entry; Atmospheric sensing; Electrospray thrusters; Molecular dynamics

SF.40.20.B0003: Atmospheric Ion Chemistry

Martinez, Oscar - (505) 853-3399

We study plasma chemistry reactions over a broad range of conditions in order to understand the natural and perturbed atmosphere. Several state-of-the-art fast flow reactors allow studies over an unprecedented range of conditions. (1) The selected ion flow drift tube can study ion-molecule reactions over the temperature range from 80-700 K and an energy range from thermal to approximately 1 eV. These data are used to derive internal energy dependences of ion/molecule reactions and to study reactive species such as atoms and radicals. (2) A high-temperature flowing afterglow can study ion-molecule reactions from room temperature up to 1800 K and electron reactions up to 1200 K. Combining the HFTA with the SIFDT data allows us to study internal energy dependences over a broader range of vibrational frequencies. (3) A turbulent flow reactor allows us to study reactivity from 10-760 Torr from room temperature to 700 K. The combination of these instruments makes it possible to study atmospheric ion chemistry under all atmospheric conditions. (4) We can also study electron processes in a flowing afterglow Langmuir probe apparatus. We study ion-molecule, electron attachment, ion-ion mutual neutralization, and electron-ion recombination. We use the data to understand numerous systems of interest to the Air Force and DOD. Examples include the natural ionosphere, plasmas around a variety of hypersonic vehicles, plasma assisted combustion, laser development, and the HAARP facility. We also look to develop techniques for mitigating and exploiting the effects of such plasmas and are developing chemical ionization techniques for detecting trace neutrals in the atmosphere, most recently for sensitive detection of chemical agents.
Keywords:Atmospheric chemistry; Atmospheric particles; Ionosphere; Atmospheric plasmas; Turbulent flows;

SF.40.20.B0002: Artificial Intelligence Opponents for Contested Space Wargaming

Erwin, R. Scott - (505) 846-9816

The research topic is centered on development of AI engines (primarily reinforcement learning approaches) to compete in a multi-player, competitive, zero-sum game involving space dynamics and space environment constraints, e.g. power, thermal, communications, etc. The project will involve developing the game itself, using openly available game engines and physics simulations, the development of AI engines using openly available environments, training/playing of games to characterize and analyze AI performance, and documenting results. The work will be collaborative with partners in academia, industry, and within the DoD Operational community.
Reference
N. A. Barriga, M. Stanescu, and M. Buro. Combining strategic learning and tactical search in real-time strategy games. CoRR, abs/1709.03480, 2017.
M. J. Kim, K. J. Kim, S. Kim, and A. K. Dey. Performance evaluation gaps in a real-time strategy game between human and artificial intelligence players. IEEE Access, PP(99):1{1, 2018.
I. Millington and J. Funge. Artificial intelligence for games. CRC Press, 2016.
D. Silver et al. Mastering the game of go with deep neural networks and tree search. Nature, 529:484{503, 2016.
Keywords:Machine Learning; Artificial Intelligence; Games; Modeling & Simulation; Reinforcement Learning; Autonomous Systems; Computer Science; Software; Programming;

SF.40.20.B0001: Advanced Computational Plasma Physics Modeling for Next Generation Technologies

White, Michael - (505) 853-8172


We are looking for motivated researchers to help develop algorithms for NextGen plasma modeling. Among the technologies of interest are relativistic non-neutral plasmas for microwave radio-frequency (RF) enhancement and laser plasma research utilizing a range of computational methods including particle-in-cell (PIC), plasma fluid modeling, and kinetic theory. Two specific areas of research are in accurate modeling of complex microwave devices and the RF generation from ultra-short pulsed laser (USPL) derived filaments. For the microwave devices, we are interested in high-fidelity, fully conformal, relativistic simulation electromagnetic-PIC of complex geometries. For USPL, we are interested in simulation of Vlasov and collisional Boltzmann equations to handle the non-equilibrium modeling of the underlying physics. Successful candidates should know an advanced programming language such as C/C++ and/or modern Fortran, as well as the basics of parallel programming for large scale computing. Experience with high-order and/or spectral methods and advanced computer architecture hardware (such as GPGPU and or coprocessor [e.g. Tesla, Phi, etc.]) programming is a plus.
References
Houard, Aurélien, Liu Y, Mysyrowicz A: "Recent developments in femtosecond filamentation". Journal of Physics: Conference Series 497(1): IOP Publishing, 2014
Shizgal, Bernard: "Spectral methods in chemistry and physics". Springer-Verlag 2015
Keywords:
Plasma; Kinetic theory; Boltzmann; Vlasov; Particle-in-cell; EM-PIC; USPL; High-order/spectral

SF.40.19.B0005: Laser Spectroscopy of Next-Generation Propellants

Annesley, Christopher - 505-846-1042

Our research centers on the chemistry of space vehicles: the reactions involved in hypergolic ignition and the subsequent interactions between the thruster plume and the near-space environment. We are currently interested in the spectroscopy, structure, and reactivity of novel ionic liquid propellants, which are being pursued as a next-generation, “green” alternative to the toxic hydrazine-based systems currently in use. Ultraviolet spectroscopy of gas-phase ionic liquid ion pairs in a supersonic jet provides optical signatures of these new compounds. Infrared spectroscopy identifies distinctive molecular vibrations, which are compared to vibrational frequencies calculated using standard computational chemistry methods. This comparison allows us to determine the ion pair structures present in the experiment, as well as to rigorously test the methods of theory employed. We are also developing an instrument which will use electrospray to transfer clusters of ionic liquids into the gas phase, where they will be stored in a cold ion trap for studies of their spectroscopy and hypergolic reactions.
Keywords: Lasers; Spectroscopy; Mass spectrometry; Propulsion; Computational chemistry; and Spacecraft Eligibility Citizenship: Open to U.S. citizens Level: Open to Postdoctoral and Senior applicants

SF.40.19.B0004: Reconfigurable free-space photonics

Lyke, James - 505-846-5812

DESCRIPTION: While software-defined / cognitive radio technologies are a vibrant area of current research, very little work has been done on the photonic equivalent of these technologies. The promise of reconfigurable free-space optical technologies is attracting for atmospheric transmission as well as through space. When we think of reconfigurability, we are in effect introducing a series of knobs throughout a system that can be adjusted through 0-1 programming decisions under the influence of heuristics, adaptively (to include cognitive algorithms). The types of variations, degrees of freedom, are limited in part by physics, in part by the imagination, but include wavelength (and the multiplicity of wavelength, to and beyond dense wavelength division multiplexing), optical pathway configuration, shaping the direction of the optical ingress/egress in transceivers (and associated apertures), and higher order considerations, such as modulation (optically coherent as well as non-coherent), forward error correction, and protocol-related considerations pertaining to framing and relationship to the various levels of a protocol stack. We must consider the notion of control plane and configuration management, as applied to field programmable gate array (FPGA) and software radio, as these manage the configuration process itself. It is possible to explore, as in software radio, the ability to exploit a flexible system for many roles. Software radios can be used, beyond communication, for metrology, signal characterization, ranging, timing, and many other applications. We expect some of these same possibilities for photonic SDRs. This is presently a field ripe for study and exploration.

Towards applications in communications, position navigation and timing, ranging and metrology, the research opportunity herein, is soliciting innovations to developing the underlying technologies of reconfigurable lasercom. Prospective researchers shall investigate necessary scientific foundations, innovative design principles, and feasible, including but not limited to: i) developing reconfigurable optical concept transceiver and routing architectures (and "middle boxes"), ii) developing concepts in fundamental reconfigurability mechanisms and considering the roles and possibilities of integrated photonics; establishing algorithmic / heuristic strategies for managing reconfigurability (i.e. adaptiveness, cognitive approaches, etc).

REFERENCES
1. Soref, Richard. “Reconfigurable Integrated Optoelectronics”, Hindawi Publishing Corporation Advances in OptoElectronics, Volume 2011, Article ID 627802

2. Lyke, James et.al., “Introduction to Reconfigurable Systems”, Proceedings of the IEEE, March 2015, Volume 103, Issue 4.

3. J. Seregelyi, "How close is the all-optical transceiver for software-defined radio?,” SPIE Newsroom, (2006) (DOI:10.1117/2.1200602.0057).

4. D. J. Geisler, C. M. Schieler, T. M. Yarnall, M. L. Stevens, B. S. Robinson, and S. A. Hamilton, “Demonstration of a variable data-rate free-space optical communication architecture using efficient coherent techniques,” Journal of Micro/Nanolithography, MEMS, and MOEMS, Optical Engineering, Vol 55, 111605:1-12 (2016). (DOI:10.1117/1.OE.55.11.111605)

SF.40.19.B0003: Application of Optical Frequency Combs in Free-Space Communication and Time Dissemination

Olson, Spencer - (505) 846-4799

Phase-stabilized optical frequency combs were first developed as a means for measuring the frequency of an optical clock (i.e. to count optical frequencies). The wide spectral coverage and femtosecond-level timing precision offered by a frequency comb makes it an attractive tool for many advanced technologies. Compact and robust frequency comb sources are now available as all-polarization-maintaing fiber lasers, which have been shown to operate outside the metrology laboratory. Moreover, micro-resonator combs offer unique promise in their wide mode-spacing and small footprint. We are developing frequency comb sources suitable for terrestrial and space applications; digital control algorithms for frequency comb stabilization; and applications that exploit the attractive features of the comb related to free-space optical time transfer, optical communications, and coherent spectroscopy.

SF.40.19.B0002: Autonomous Processing Techniques for Applications in Space

Mee, Jesse - (505) 846-3749

The next generation of exquisite sensors being developed by the DoD and the IC will provide unparalleled advantages for intelligence surveillance and reconnaissance; however, these sensors produce extraordinary amounts of raw data. The rate of data coming off of these sensors threatens to outpace our capacity to transmit bits to the ground station and overwhelms the on-board memory resources. Consequently, we must consider options for processing raw data on the spacecraft, and distilling that data into actionable information that can be sent to an analyst on the ground, or used by the spacecraft to take autonomous action.
In response, the Air Force Research Laboratory (AFRL) established a dedicated architecture test-bed under the Spacecraft Performance Analytics and Computing Environment Research (SPACER) project. The SPACER lab exists to provide guidance on how to improve the on-orbit processing capabilities of national security space systems by leveraging commercial industry processing technologies such as heterogeneous multi-processor system on a chip architectures for low power mobile phone processors, or neural networks architectures for autonomous vehicle operation and big data analytics.
Currently we seek an applicant with a background in neuromorphic computing. Our research interests center on understanding the suitability of neuromorphic architectures to solve computationally complex image processing applications for the Air Force. The effort will start with an assessment of neural networks instantiated using digital logic, but is expected to evolve toward a cortical processing approach. Cortical processing is distinguished from neuromorphic processing by the following features: online “continuous” training, hierarchical memory architecture, and a feedback between input sensor and the neural substrate. A detailed assessment of the energy and performance consequences of a digital CMOS implementation versus neuromorphic or cortical implementation of an image processing algorithm is desired. The specifics of the algorithms under consideration will be given at a later date. The SPACER architecture test-bed allows researchers to address the increasing challenge of mapping mission requirements to hardware and software implementations for space computing applications, and provides multiple challenging research opportunities for an enthusiastic applicant.
References:
1.Erik P. DeBenedictis, Jesse K. Mee, Michael P. Frank, “The Opportunities and Controversies of Reversible Computing,” IEEE Computer, vol. 50, no. 6, pp. 76-80 (2017)
2.J. Lyke, J. Mee, A. Edwards, A. Pineda, E. DeBenedictis and M. Frank, "On the energy consequences of information for spacecraft systems," 2017 IEEE International Conference on Wireless for Space and Extreme Environments (WiSEE), Montreal, QC, Canada, pp. 104-109 (2017)
3.Jesse Mee, Andrew Pineda, Reed Weber, Phillip Cunio, and Keith Avery, “Architecture Investigation for Future Space Processing,” Hardened Electronics and Radiation Tech. Conf., Monterrey, California (2016)
4.A. C. Pineda, J. K. Mee, R. Webber and P. Cunio; “Benchmarking Image Processing for Space: Introducing the SPACER Architecture Laboratory,” IEEE Aerospace, Accepted, Big Sky, Montana (2016)
Keywords:Spacecraft; Embedded System; Machine Learning; Artificial Intelligence, Neuromorphic, Architecture; Optimization;

SF.40.18.B0008: Relativistic Time Synchronization for Satellite Crosslinks

Pham, Khanh - 505-846-4823

With an outlook towards flexible GPS-surrogate technologies, this research opportunity is seeking time transfer and synchronization approaches for satellite constellations equipped with crosslink capabilities. Spedifically, scientific breakthroughs are needed for time signals of onboard clocks to be transferred and synchronized through crosslinks, including gravitational effects such as Shapiro delays. The endpoints of these crosslinks are satellites with clocks in orbital motions; e.g., moving at 3 km per second for Geo-synchronous Orbits and 7 km per second for Low Earth Orbits. What follow are some technical challenges of interest, including: i) modeling, simulation and analysis of relativistic time transfers in radio and/or optical clocks; ii) compensation of Shapiro delays and other propagation effects; iii) distributed time transfer mechanisms in radio and/or optical crosslinks; iv) stability and consensus in remote time dissemination; and v) accurate processing of crosslink data for time synchronization accuracy and convergence.
REFERENCES
1. D.W., Hanson, “Fundamentals of Two-Way Time Transfer by Satellite,” Proceedings of 43rd Annual Symposium on Frequency Control, pp. 174-178, 1989
2. D. Kirchner, “Two-Way Time Transfer via Communication Satellites,” Proceedings of IEEE, Vol. 79, No. 7, pp. 983-990, 1991
3. J. Miller, et. al. “NASA Architecture for Solar System Time Distribution,” Proceedings of IEEE Frequency Control Symposium, pp. 1299-1303, 2007
4. Y. Xie, “Relativistic Time Transfer for Inter-satellite Links,” Frontiers in Astronomy and Space Sciences 3, 2016
KEYWORDS:
GPS Denied, Time Synchronization, Distributed Time Transfer, Onboard Processing, Crosslinks, Shapiro Delay, Synchronization Accuracy, Propagation Effects

SF.40.18.B0007: Onboard Satellite Synchronization for Frequency Hopping Spread Spectrum Waveforms

Pham, Khanh - 505-846-4823

Synchronization in satellite communications is the process of aligning the time and phase scales of satellite ground hubs, satellite transponders and user terminals such that the equipment operations occur at correct times and correct phases in correct orders. First, time synchronization requires the clocks at receiver ends to acquire and track periodic timing information in transmitted signals. Second, phase synchronization requires receiver carrier tracking loops to acquire and track carrier phase information in transmitted signals. There are several methods to obtain time and phase information through commercial communications infrastructures, including both coherent and non-coherent frequency hopping demodulations; however, levels of trust, accuracy, and robustness of these mechanisms limit potential usefulness for military communications missions. Prospective onboard satellite synchronization paradigms ought to consider the following technical challenges: i) analysis of time and phase errors associated with ground satellite system controllers; ii) technical requirements of modeling for time and phase errors for user terminals; iii) uncertainty quantification and management of onboard satellite transponder’s timing and phase errors; iv) performance assessment of both open-loop and closed loop synchronization techniques for phase and timing jitters per hop and/or potential onboard computation solutions for fast phase and time synchronizations in the presence of radio interferences.
REFERENCES
1. T. M. Schmidt and D. C. Cox. “Robust Frequency and Timing Synchronization for OFDM,” IEEE Transactions on Communications, Vol. 45, No. 12, pp. 1613-1621, 1997
2. H. Minn, V. K. Bhargava and K. B. Letaief. “A Robust Timing and Frequency Synchronization for OFDM Systems.” IEEE Transactions on Wireless Communications, Vol. 2, No. 4, pp. 822-839, 2003
3. Chit-Sang Tsang, Tien M. Nguyen, “Long Loop Time Tracking Performance for Satellite Communication System,” IEEE MILCOM Proceedings, pp. 855- 959, 1999
4. P. J. Duffett-Smith and P. Hansen, “Precise Time Transfer in a Mobile Radio Terminal,” Proceedings of the 2005 National Technical Meeting of the Institute of Navigation, pp. 1101-1106, 2005
5. T. M. Nguyen, J. Hant, D. Taggart, C.-S. Tsang, D. M. Johnson, J.-C. Chuang, “Design Concept and Methodology for the Future Advanced Wideband Satellite System,” IEEE MILCOM Proceedings, pp. 189-194, 2002
KEYWORDS: Satellite Communications, Radio Interference, Frequency Hopping Spread Spectrum, Timing Synchronization, Phase Synchronization, Timing Jitter, Timing and Phase Errors, Transponder Timing Errors, Closed-Loop Synchronization, Open-Loop Synchronization

SF.40.18.B0006: Topology Formation and Network Coding for Multi-source Multicast Satellite Communications Networks

Pham, Khanh - 505-846-4823

Satellite communications networks are characterized by high bandwidth and ease of mobility with minimum coverage cost. But when certain network topologies; i.e., Geo-synchronous Orbit (GEO) satellites with fixed terminals, GEO with mobile terminals, and Low Earth Orbit satellites, are of concern, high computational complexity issues arise because of network topology characteristics, so many of the network formations that give optimal performance are required to find scalable and stable solutions subject to large sizes and mobility of the networks. Primary interests of this research opportunity are in integrated systematic approaches and guidelines for overlay protocols that interface with either the transport layer or lower layers. Specifically, distributed network topology formations with polynomial complexity are desired to automatically endow nodes in the network some autonomy to decide whether to make links with neighbor nodes or not, while considering the cost required for link formation. In addition, with respect to the bottleneck issue incurred by the multi-source multicast flows, network coding is being considered as a promising technique that is capable of enhancing efficient resource usage and improving robustness and throughput.
REFERENCES
1. S. Kamamura, A. Fukuda, et. al., “Resolution of Network Topology using Fast Graph Mining,” IEEE ICC 2017 Communications QoS, Reliability, and Modeling Symposium, 2017
2. C. Liang and F. R. Yu, “Enhancing Mobile Edge Caching with Bandwidth Provisioning in Software Defined Mobile Networks,” IEEE ICC 2017 Mobile and Wireless Networking, 2017
KEYWORDS: Satellite Communications, Topology Formation, Network Coding, Multi-source Multicast Networks

SF.40.18.B0005: Integrating Performance Enhanced Proxies with Bundle Protocols over High Assurance Internet Protocol Encryptions

Pham, Khanh - 505-846-4823

Today, almost all of Disruption Tolerant Networking (DTN) architectures are based on the Bundle layer between Transport and Application layers. By installing DTN Bundle protocols on end-points and on nodes at the border of homogeneous segments, the resulting end-to-end paths are divided in many DTN hops. On each DTN hop a different protocol stack can be used, like Transport Control Protocol (TCP) or User Datagram Protocol (UDP), or different versions of the same protocol. In essence, data transfers from DTN senders to DTN receivers are now provided by the Bundle protocols, which exchange large data packets, called “bundles”, between DTN nodes through a store-and-forward relay mechanism. On the other hand, recent research and development ventures have introduced Performance-Enhancing Proxies (PEPs), which are network agents designed to improve end-to-end performance of some communications protocols. Most satellite-optimized PEPs use TCP splitting techniques based on Space Communications Protocol Specifications-Transport Protocol (SCPS-TP). They are intended to address satellite impairments by isolating satellite segments from the rest of the network. But with the advent of High Assurance Internet Protocol Encryptions (HAIPEs), both DTN and PEP now face a common problem in the presence of HAIPE devices. Specifically, the use of Internet Protocol security (IPsec) end-to-end encryption of HAIPEs prevents Bundle or PEPs from viewing or modifying TCP headers. Bundle cannot process the store-and-forward scheme and PEPs cannot transparently break the end-to-end TCP connections to substitute their own protocols over satellite links. Consequently, Bundle and PEPs are often disabled when used with HAIPEs, and thus network bandwidths in SATCOM links are not fully utilized.
Towards increasing SATCOM throughputs while minimizing intrinsic delays and disruptions, the research opportunity herein, is soliciting innovations to integrate Bundle with PEPs and HAIPE seamlessly. Prospective researchers shall investigate necessary scientific foundations, innovative design principles, and feasible add-on modules, including but not limited to: i) integrating PEPs into Bundle protocols and ii) handing Bundle and PEP protocol data within IPsec tunnels.
REFERENCES
1. R. Amin, D. Ripplinger, D. Mehta and B. N. Cheng, “Design considerations in applying disruption tolerant networking to tactical edge networks,” IEEE Communications Magazine, Vol. 53, No. 10, pp. 32-38, 2015.
2. C. Caini, P. Cornice, R. Firrincieli, M. Livini and D. Lacamera, “TCP, PEP and DTN performance on disruptive satellite channels,” Int’l Workshop on Satellite and Space Comm, pp. 371-375, 2009
KEYWORDS: DTN, Bundle, PEP, HAIPE, network throughput, delays, SATCOM, TCP flows, store-and-forward, IPsec, cyber threats, confidentiality, and efficiency

SF.40.18.B0004: Enhanced and Assured Radio Frequency Downlinks

Pham, Khanh - 505-846-4823

DESCRIPTION: This research opportunity seeks to enhance data rates and resiliency in radio frequency (RF) downlinks in existing satellite constellations. Specifically, the research endeavor is investigating alternative waveforms to downlink all necessary and most of the desired evolved sensor data from a variety of orbits without increasing existing data rates and bandwidths to support existing ground elements. Moreover, it is reasonable to expect that potential technical solutions would integrate existing cognitive radio technologies to enhance current data rates and resiliency of Air Force assets with minimal impacts to their existing infrastructures. If successful, future universal waveforms and modems supported by the findings anticipated herein would be inserted in conjunction with existing satellite operation centers, fixed site access networks, tactical platforms and users. As for the technical challenges, prospective researchers shall investigate necessary scientific foundations, design principles, and/or add-on modular components, including but not limited to: i) universal waveforms that can encapsulate existing waveforms and further transport them in the presence of contested radio environments; ii) enhanced RF downlink concept of operations in the presence of unintentional and intentional radio interference sources using cognitive radio technologies; iii) resilient carrier frequency, bandwidth, burst duration and burst repetition interval parameters for RF downlinks with low probability of detection and interception; and iv) achieving unjammed throughput efficiency in contested radio environments.
REFERENCES
1. C4ISR for Future Naval Strike Groups, “Chapter: 7 Intelligence, Surveillance, and Reconnaissance,” The National Academies Press, pp. 175-282, 2006
2. T. M. Nguyen, J. McWilliams and M. Hammond, “R-CDL Communication Closes the NT-ISR Information Gap,” Raytheon Tech Today, Issue #3, 2007
KEYWORDS: RF Downlinks, Universal Waveforms, Add-on Modules, Modular Open System Architectures, Carrier Frequency, Bandwidth, Burst Duration, Burst Repetition, Contested Radio Environments

SF.40.18.B0003: Nonlinear Dynamics in Spacecraft Guidance, Navigation, and Control

Sinclair, Andrew - (505) 846-0197

This project seeks to develop improved methods for spacecraft guidance, navigation, and control (GNC) through improved understanding of the spacecraft nonlinear dynamics. Spacecraft translational motion is dominated by orbital dynamics and the control is often constrained by a limited fuel supply. Therefore, translational GNC methods generally must be designed to work with these dynamics instead of fighting them. Spacecraft attitude motion is governed by the particular structure of rotational dynamics and robust performance of attitude GNC methods depends on careful adherence to this structure. Additionally, spacecraft operations are subject to significant nonlinear control-estimation interactions, an example being the lack of observability of control-free relative motion in close proximity when using angles-only measurements. Another example is visual-serving attitude control for object tracking by space-based sensors for space situational awareness. Research proposals that address one or more of these topics from a theoretical or experimental point of view are of interest. This research can use the experimental facilities at AFRL, including a spherical air bearing attitude control and determination testbed and autonomous multi-spacecraft testbed.
References
Jagat A, Sinclair AJ: “Control of Spacecraft Relative Motion Using Angles-Only Navigation”. AAS 15-444, AAS/AIAA Space Flight Mechanics Meeting, Williamsburg, Virginia, January 11-15, 2015
Sinclair AJ, Sherrill RE, Lovell TA: “Use of Cartesian-Coordinate Calibration for Satellite Relative-Motion Control”. Journal of Guidance, Control, and Dynamics 38(9): 1842-1847, 2015
Hurtado JE, Sinclair AJ: “State Transition Matrix, Motion Constants, and Ergodicity of the Euler-Poinsot Problem”. Nonlinear Dynamics 85(3): 2049-2063, 2016
Sinclair AJ: “Calibrated and Decalibrated Approximations of Nonlinear Dynamic Systems”. Nonlinear Dynamics 87(1): 281-290, 2017
Keywords:Spacecraft; Dynamics; Guidance; Navigation; Control; Orbit; Attitude; Robotics;

SF.40.18.B0002: The Effect on Material Properties (and the Underlying Chemistry) Due to Exposure Simulated Space Environment

Engelhart, Daniel - (505) 846-6945

Space is complex and a hostile environment. It consists of vacuum, large temperature fluctuations, and bombardment by energetic particles, including atomic oxygen, electrons, ions, vacuum ultraviolet light (VUV), all of which act to alter the materials spacecraft are constructed from. Our research effort focuses on the modification of spacecraft material properties caused by exposure to the space environment, predominantly bombardment by high energy electrons, ions, and VUV light.
Previously, experiments on common spacecraft polymers such as polyimide (Kapton®), or polytetrafluoroethylene (Teflon®) have shown dramatic changes in the electrical conductivity, an important parameter for spacecraft survivability, when radiated with high energy electrons. Current research is underway to understand the chemical underpinnings of these changes and extend that understanding to other material properties especially optical. We are searching for an Associate to undertake experiments and/or modeling to provide chemical understanding of polymer degradation and prediction of the material properties after exposure to a known radiation environment.
Optical properties of materials provide an exciting link to understand the state of a satellite using remote sensing. The end goal is to use various photometric measurements generated during this work to determine the material composition of a satellite and the state of each material.
The Associate will have access to a large vacuum chamber (2m diameter) equipped with a high energy electron gun, VUV lights, a temperature regulated plate, and several characterization tools. In addition the lab has access to AFM, SEM, UV/VIS and IR spectrometers, and optical characterization facilities, either in the lab or with collaborators on base. Ongoing collaborations with the University of New Mexico, other research universities, and the materials branch of AFRL provide access to practically any material characterization technique.
Reference
Cooper R, et al: Effects of Radiation Damage on Polyimide Resistivity. Journal of Spacecraft and Rockets, 2016, accepted, DOI: http://dx.doi.org/10.2514/1.A33541
Keywords:Material science; Polymer; Space weather; Computation; Degradation; Radiation; Optics; Charge transport; Remote sensing;

SF.40.18.B0001: Advanced Algorithm Development for Guidance, Navigation, and Control for Spacecraft

Erwin, R. Scott - (505) 846-9816

This project seeks to develop new methods, techniques, and algorithms for challenging spacecraft guidance, navigation, and control (GNC) problems. Specifically, this topic seeks to (1) develop improved guidance and control algorithms that provide improved robustness and performance in the face of systemic uncertainties (e.g., modeling errors), are adaptive to such errors to enable performance in spite of errors, provide solutions for mission assurance and mission safety (e.g., fail-safe qualities), enable efficient use of spacecraft resources (fuel, power, etc.), and are reconfigurable based on shifting mission priorities; and (2) develop improved estimation algorithms for relative and inertial navigation that process alternative signals and measurements onboard the spacecraft such that accurate and robust navigation solutions under system uncertainties are guaranteed. Research proposals that address one or more of these topics from a theoretical or experimental point of view are of interest. This research can use the experimental facilities at AFRL, including a spherical air bearing attitude control and determination testbed, image-based spacecraft navigation facilities, rendezvous & proximity operations simulation capabilities, and autonomous multi-spacecraft testbeds.
Keywords: Spacecraft; Guidance; Control; Navigation; Dynamics; Estimation; Optimal; Autonomous; Signals;

SF.40.17.B0007: Spacecraft Performance Analytics and Computing Environment Research

Mee, Jesse - 505.846.3749

The current methods for the identification of future technological capabilities required to support next-generation DOD systems lack the quantitative sophistication and detail needed to compare system gains resulting from Size, Weight and Power (SWaP) and performance improvements at the device/component level. Furthermore, owing to the increasing complexity of modern computing architectures, there is no longer a trivial approach toward selection of onboard hardware resources necessary to meet future Air Force mission needs. To address these concerns, the Air Force Research Laboratory (AFRL) has recently established a dedicated architecture test-bed under the Spacecraft Performance Analytics and Computing Environment Research (SPACER) project. This test-bed allows researchers to address the increasing challenge of mapping mission requirements to hardware and software implementations for space computing applications. This multifaceted project provides multiple challenging research opportunities for an enthusiastic applicant. In particular, we are seeking support with identification and design of the optimized heterogeneous computing architecture for a specialized mission application code. This effort will require decomposition of the application code into a sum of its low level computational pieces (e.g., FFT, Matrix-Matrix multiply), benchmarking of those computational pieces on the test-bed hardware resources, and design of an optimized hardware platform for the mission. In another effort, we seek to develop a satellite system level model that enables creation of a performance trade-space characterizing top-level mission impacts as a function of modifications at the individual component level. This model allows the user to capture the satellite component hierarchy, define the complex time-varying power characteristics, and propagate the model through an orbital simulation to study the on-orbit energy utilization of the candidate architecture. If executed properly, this effort will provide a valuable capability to the Air Force, enabling a more quantitative approach to justification of future research investments, in addition to a better understanding of computational requirements for next generation mission applications

References
Pineda AC, Mee JK, et al: Benchmarking Image Processing for Space: Introducing the SPACER Architecture Laboratory. IEEE Aerospace, Accepted (2016) Mee JK, et al: Energy Accounting Model for Hardware Impact Analysis. IEEE Aerospace, Accepted (2016)

Keywords:
Spacecraft; Embedded system; Computer; Architecture; Model; Simulation; Efficiency; Performance; Optimization; Eligibility
Citizenship: Open to U.S. citizens
Level: Open to Postdoctoral and Senior applicants

SF.40.17.B0006: Ionosphere-Thermosphere Coupling-Data Analysis and Numerical Simulations

Huang, Cheryl - 505.846.7218

Understanding the Ionosphere-Thermosphere (IT) system is crucial for accurate forecasting of the impact of space weather. We solicit proposals to investigate high-latitude IT coupling via a combination of data analysis and numerical simulations during conditions of solar wind forcing. Data analysis should include sources from ground and space to be as comprehensive as possible. We encourage innovative physics-based model solutions aimed at improving forecast ability in real time. Model results should be validated by comparison with data.

References
Huang CY, et al: Ionosphere-thermosphere (IT) response to solar wind forcing during magnetic storms. Journal of Space Weather and Space Climate 6 A4: 2015, doi: 10.1051/swsc/2015041 Huang CY, et al: Energy coupling during the August 2011 magnetic storm. Journal of Geophysical Research: 1219-1232, 2014, doi: 10.1002/2014JA019297 Huang Y, Huang CY, et al: Ionization due to electron and proton precipitation during the August 2011 storm. Journal of Geophysical Research, doi:10.1002/2013JA019671 2014

Keywords:
Ionosphere; Thermosphere; Solar wind forcing; Space weather; Physics-based models; High-latitude IT coupling; Eligibility
Citizenship: Open to U.S. citizens
Level: Open to Postdoctoral and Senior applicants

SF.40.17.B0005: Fundamental Investigation of Plasma Chemistry Kinetics and Dynamics towards Improved Communications Abilities

Shuman, Nicholas - 505.853.3966

The propagation, refraction, or reflection of radio waves through weakly ionized plasma (e.g., the natural ionosphere) is most succinctly understood by comparison of the frequency of the radio wave to the critical frequency of the plasma, a function of the electron density. The electron density in turn is determined by the chemistry of charged species present in the plasma. Decades of research into the ion chemistry of the ambient ionosphere have provided a solid foundation for modeling and prediction of radio wave propagation under a range of conditions. More recent interest has been focused on “artificial” ionospheric conditions, either those produced incidentally by effects of hypersonic objects (e.g., re-entry vehicles) or those produced intentionally via ionospheric modification. Much of the basic chemistry under the temperature and pressure conditions required to model these environments is unstudied. This includes ion-molecule, electron attachment, mutual neutralization, and dissociative recombination processes at elevated temperatures, a range of pressures, and over non-thermal conditions.
We are particularly interested in reactions resulting in spontaneous ionization, offering a means to increase the local electron density over a region of the lower ionosphere. A number of the lanthanide rare earth metals along with a handful of transition metals possess energetics where chemi-ionization (e.g., A + B ? AB+ + e) is exothermic with either atomic oxygen or oxygen-containing species. Release of these metals in the E-region of the ionosphere, where atomic oxygen is a dominant neutral species, provides an avenue to creating a cloud of enhanced electron density. However, the kinetics of these processes has been only minimally explored and the energy dependences generally unexplored. Additionally, the related ion chemistry is in nearly all cases unknown. Vaporization of these metals in an oven source coupled to a flow tube reactor provides a route to studying the chemi-ionization kinetics and products. Electrospray ionization of solutions of these metals allows for production of the ionized metal and metal oxides in the gas phase, and determination of the kinetics of those species through standard techniques. The results of these measurements can be directly transitioned to models of chemical releases in the ionosphere, aiming to account for both the associated physics and chemistry, to interpret results of prior chemical release experiments and to determine the relative efficacy of different species under consideration for future experiments.

References
Shuman NS, Hunton DE, Viggiano A: Ambient and modified atmospheric ion chemistry: From top to bottom. Chemical Reviews 115: 4542-4570, 2015 Cox RM, et al: Evaluation of the exothermicity of the chemi-ionization reaction Sm + O ? SmO+ + e-. The Journal of Chemical Physics 142: 134307, 2015

Keywords:
Plasma chemistry; Ionosphere; Electron attachment; Chemical physics; Radicals; Ion-molecule; Flow tube; Kinetics; Dissociative recombination; Eligibility
Citizenship: Open to U.S. citizens
Level: Open to Postdoctoral and Senior applicants

SF.40.17.B0004: Development of Ultrahigh Temperature Chemistry Models for Hypersonic Flow

Bemish, Raymond - 505.853.2776

Atmospheric reentry vehicles produce large amounts of heat and plasma due to the high Mach number. This process is primarily driven by the non-equilibrium high-temperature chemistry that is present in the bow-shock and the gas surface interactions. Due to the high temperature, in excess of 20,000K, it is difficult to experimentally derive meaningful values. A combination of theory and flight/ground test data is used to validate these models. For this reason, it is necessary to develop physics based models for all of the drivers in hypersonic flight and use the combined effects to produce a high fidelity simulation of the flight. This allows for optimization and validation of the chemical models. This effort supports development of all the constituent physics and chemistry for a high fidelity hypersonic flight solution.

Keywords:
Spacecraft; Actuator; Control; Allocation; Fault; Anomaly; Optimal; Tolerant; Identification; Eligibility
Citizenship: Open to U.S. citizens
Level: Open to Postdoctoral and Senior applicants

SF.40.17.B0002: Advanced Space-based Imaging Field Campaigns, Data Analyses and Cloud Characterization

Pereira, Wellesley - 505.853.3624

This effort focuses on planning, conducting, and analyzing data collection events from an extended space-based imaging campaign using an advanced remote-sensing methodology developed at the AFRL Space Vehicles Directorate. This data collection campaign (which leverages space-based imagery of ground events, with ground-based truth sensors) is intended to help validate unique methods in advanced infrared sensing, and as such must take place under carefully-monitored conditions, at specific locations in the world. The field campaign will consist of coordinated data collection events using exquisite sensing assets to observe high-radiance, short-duration events, which necessitates careful advance planning. Coordination of practical details, including timing of events, coordination of assets, collaboration with domestic and international partners, and management of data collection requirements, is important to this effort.
Furthermore, uncertainties associated with the presence of clouds when imaging from space have to be taken into consideration. To accomplish this goal, a diverse network of retrieved measurements must be statistically data mined from both up- and down-looking sensors. These include the following:
(1) AERONET (Aerosol Robotic Network), a network of globally distributed instruments which operate in a cloud-mode acquisition and measure a variety of atmospheric and cloud parameters, including cloud optical depths between 10 and 90.
(2) Micro Pulse Lidar Network (MPLNET) which measures aerosol cloud vertical structure continuously, day and night.
(3) Ceilometers at major airports which provide cloud base heights.
(4) MODIS Cloud Product, a global product that provides cloud particle-phase, effective cloud particle radius, and cloud optical thickness.
(5) Other global satellite cloud datasets as needed.
The various datasets are needed to resolve the point source measurements (AERONET, MIPLNET and ceilometers) to the satellite kilometer-scale footprints. Researching and resolving the highlighted issues requires a solid background in programming and atmospheric physics to perform data mining techniques and develop algorithms appropriate for effective cloud optical depth retrievals. Additionally, skills in data analysis, including implementing advanced analysis routines and conducting comparative analyses, are important, as is an ability to communicate technical material in writing or orally. Key technical background areas include electro-optical sensors, infrared imaging, cloud physics and/or atmospheric transmission, as well as hands-on experience. Additionally, an ability to travel to field locations is desirable.

Keywords:
Advanced imaging; Space-based imaging; Cloud statistics; Cloud optical depth; Atmospheric transmission; Eligibility
Citizenship: Open to U.S. citizens
Level: Open to Postdoctoral and Senior applicants

SF.40.17.B0001: Spacecraft Materials Properties for Spacecraft Charging

Ferguson, Dale - (505) 846-1566

This opportunity consists of measuring, analyzing, and evaluating spacecraft materials properties that have a direct bearing on spacecraft charging (i.e., bulk and surface resistivities, dielectric constants, secondary electron emission, and photoemission). Measurements of materials properties and/or charging of materials under electron beam irradiation will be made using laboratory facilities at the Kirtland Air Force Base in Albuquerque, New Mexico. Special attention will be paid to changes of materials properties and spacecraft charging with temperature, contamination, radiation dose, and/or vacuum aging.

Keywords:
Spacecraft charging; Materials properties; Space environment; Eligibility
Citizenship: Open to U.S. citizens
Level: Open to Postdoctoral and Senior applicants

SF.40.16.B0003: Communication Signaling and Signal Transmission in Low Probability of Interception Communications

Pham, K - (505)-846-4823

At the center of covertness and survivability issues of Low-Probability-Interception (LPI) communications is the development of communication signaling techniques and signal transmission schemes that are changing courses due to primarily to uncertain channel quality measurements, multi-access interferences, frequency-selective fading, partial band noise jamming, feedback delays, etc. Quantitatively speaking, it is important to investigate error performance analyses and related interpretations for M-ary-frequency-shift-keying systems employing L-hops per bit frequency hopping spread spectrum waveforms, transmitted over thermal noise plus partial-band Gaussian noise jamming channels. Performance measures should be computing processor dependent and further subject to different types of receiver processing techniques, e.g., square-law combining receiver, adaptively gain controlled square-law combining receiver, partially-jammed-hop elimination receiver, and clipped square-law combining receiver. A further concern involves hopping keystreams, which come from an end cryptographic unit at a user terminal. These frequency hopping patterns are more likely independent of channel conditions. In light of current practices, it becomes clear that the central question is then to ask whether or not L-hops per bit frequency hopping M-ary frequency-shift-keying spread spectrum systems with adaptive frequency hopping patterns ensure LPI communications more effectively; i.e., yielding of lower bit error rates, frame error rates against partial-band noise jamming under all possible operating situations? If yes, relevant technical challenges of developing adaptive frequency hopping patterns based on imperfect channel state information (CSI), jamming state information (JSI) in both time and frequency domains should be of interests. On another front, yet not too far removed from covert communications, possibly lies research and development of interest bearing on the scope of properly designing waveforms for LPI applications with two set of requirements: i) an unauthorized interceptor must not be able to detect the presence of the waveforms with probability greater than some specified small number – detection aspect; and ii) an authorized receiver can extract the information content with an acceptably low error probability – communication aspect. References: 1. L. Schiavone and D. Hendry, “EHF Options for Contested SATCOM,” IEEE Military Communications Conference, MILCOM, 2011. 2. Y. Kawamoto, et.al., “Prospects and Challenges of Context-Aware Multimedia Content Delivery in Cooperative Satellite and Terrestrial Networks,” IEEE Communication Magazine, 2014. 3. S. Lambotharan and A. Panoui, “Game-Theoretic Framework for Radar Waveform Design,” 2014. 4. G. Wang, K. Pham, E. Blasch, T. M. Nguyen, G. Chen, et. al., “Optimum design for robustness of frequency hopping system,” IEEE Military Communications Conference, 2014. Eligibility: Open to U.S. citizens Only

SF.40.16.B0002: Cooperative Spectrum Sensing with Multi-Dimension Directions for Protected Tactical Satellite Communications

Pham, K - (505)-846-4823

As future satellite communications (SATCOM) networks will have access to an increasing amount of data, protected tactical services in contested environments will be enabled by cooperative spectrum sensing among distant user terminals, satellite control hubs, and other SATCOM networks. Sensing information exchange and fusion of throughput, data queue sizes, spectrum maps, signal-to-noise ratio information should be obtained with less overhead and more bandwidth efficiency. Uncertainty of sensing results and channel conditions also have large impacts on spectrum management for potential resolutions on miss-configurations and spectrum command and control. Work focuses on this research topic related to necessary scientific foundations and design principles for affordability, within which cooperative spectrum sensing with multi-dimension directions; e.g., dynamic signal measurements, modulation classifications, and spectrum masks, must deal with a number of technical challenges in both network and physical layers for satellite carrier monitoring and reporting as well as radio interference and spectrum situational awareness. Given a concept of operations pertaining to multiple SATCOM terminals and ground hubs, opportunities are available to investigate, including but not limited to: (i) Cooperative spectrum sensing with information exchange and adaptive channel allocation schemes for efficient and effective estimations of carrier, noise, center frequency, bandwidth and other parameters; (ii) Machine learning with carrier-under-carrier case studies to determine elusive radio threats blending with intended signals; (iii) Alternatives with reduction of sensing overhead and energy cost for spectrum time-domain analysis such as max hold, min hold, and average power in channel; and (iv) Uncertainty analysis of sensing results in various channel conditions and interference types. References: 1. R. A. Poisel, Modern Communications Jamming Principles and Techniques. Second edition, Artech House, 2011 2. H. Sun, A. Nallanathan, C. Wang, and Y. Chen, “Wideband Spectrum Sensing for Cognitive Radio Networks: A Survey,” IEEE Wireless Communications, Vol. 20, No. 2, pp. 74-81, 2013. 3. K. P. Murphy, “Machine Learning: A Probabilistic Perspective,” The MIT Press, 2012 4. X. Tian, Z. Tian, E. Blasch, et.al, “Sliding Window Energy Detection for Spectrum Sensing under Low SNR Conditions”, Wiley`s Journal on Wireless Communications and Mobile Computing, 2015 Keywords: Satellite communications, protected tactical services, spectrum situational awareness, cooperative spectrum sensing, carrier, noise, modulation classification, spectrum mask, radio interferences, link layer, physical layer, signal measurement, spectrum efficiency, max hold, min hold, average power, energy efficiency, sensing efficiency, sensing accuracy, game theory, machine learning, uncertainty analysis Eligibility: Open to U.S. citizens Only

SF.40.16.B0001: Baseband Diversity Product Approaches for Protected Wideband Satellite Communications

Pham, K - (505)-846-4823

Opportunities exist to explore Baseband Diversity Products (BDP) with flexibility options to operate in contested environments to maintain connectivity, improve link availability, reliability, and resilience, while at the same time confounding adversarial attempts to intercept and/or detect communications signals in wideband satellite communications. The implication of the diversity via satellite transponders, non-contiguous bandwidths, coverage beams, antenna polarizations, and multiple media, is that baseband traffics such as video, voice, and data could be disintegrated and integrated according to dedicated and/or opportunistic network path flows for optimal end-to-end latency, transmission reliability, information security, and bandwidth utilization. This topic seeks to develop new approaches for innovative data stream splitter supervised by link information feedback (e.g., data rates, latency, modulation, channel coding, etc.) and quality of services per applications; adaptive load balancing for multi-path routing and flow control with best efficiency and reliability; and agile code/frequency/time-hopping transmission patterns for satellite communications with low probability of detection and interception as well as multiple link flow security. If successful, the BDP technologies anticipated for future terminal communications, which will be inserted in between routers and satellite modems, should be capable of i) supporting multiple network topologies for high speed data, voice, and video communications over terrestrial and satellite networks and ii) processing multiple streams simultaneously and interfacing with multiple commercial and military modems to support anti-jamming enhancement and ease of integration. References: 1. X. Zhang, G. Wang, X. Tian, D. Shen, K. Pham, E. Blasch, and G. Chen.” Game-Theoretic Power Allocation and Waveform Selection for Satellite Communications”, SPIE Defense and Security, 2015 2. W. Yu, S. Wei, G. Xu, G. Chen, K. Pham, E. P. Blasch, and C. Lu, “On Effectiveness of Routing Algorithms for Satellite Communication Networks”, SPIE Defense, Security, and Sensing Symposium, 2013 3. W. Yu, X. Fu, E. Blasch, K. Pham, D. Shen, G. Chen, and C. Lu, “On Effectiveness of Hopping-Based Spread Spectrum Techniques for Network Forensic Traceback,” International Journal of Networked and Distributed Computing – Atlantis Press, 1(3), 2013 Keywords: Baseband Diversity Product, SATCOM, Terminal Communications, Data Fragmentation, Anti-Jamming, Flow Control, Link Information Feedback, Stream Splitter, Load Balancing, Data Rate, Latency, Jitter, Stream Status, Delay, Multi-path Routing, Quality of Services, Protection, Connectivity, Availability, Link Security Eligibility: Open to U.S. citizens Only

SF.40.14.B1116: Resilient System Controllers for Wideband Global SATCOM

Pham, Khanh - 505-846-4823

The increasing demand for beyond-line-of-sight and in-transit space communications is leading to an emerging growth area for secure and resilient communications. Specifically, handling efficiently jamming resistance, low probability of interception, low probability of detection, etc. is essential for future capability enhancements expected from Wideband Global SATCOM (WGS). In this research opportunity, modeling, simulation and analysis associated with ground hub satellite system controllers are being investigated to account for (i) dynamic resource allocation enabled by competitive decision-making frameworks for radio resources and link margin assignments that can best respond for airborne and/or ground terminals in presence of radio interferences and in accordance with channel-state information feedback and (ii) forward and return link multiple accesses supported by universal modulation and demodulation techniques together with frequency-time burst approaches to transport existing WGS waveforms through contested environments.
REFERENCES:
1. D. Shen, Z. Shu, X. Tian, G. Chen, and K. Pham, “A Game-Theoretic DRA Approach for Improved Spread Spectrum Frequency Hopped Waveforms Performance in the Presence of Smart Jammers,” IEEE Cognitive Communications for Aerospace Applications Workshop, Cleveland, OH, 2017
2. J. Lu, L. Li, E. Blasch, K. Pham, D. Shen, and G. Chen, “Dynamic Multi-Arm Bandit Game based Multi-Agent Spectrum Sharing Strategy Design,” IEEE/AIAA 36th Digital Avionics Systems Conference, St. Petersburg, FL, 2017
3. X. Tian, G. Chen, K. D. Pham, and E. Blasch, “Joint Transmission Power Control in Transponded SATCOM Systems,” IEEE Military Communications Conference, Baltimore, MD, 2016
KEYWORDS: WGS SATCOM; Dynamic resource allocation; System controllers; Airborne and/or ground terminals; Low probability of interception; Low probability of detection; Radio interferences; Dynamic resource allocation decision processing; Link margin assignment; Forward and return multiple access; Frequency-time burst; WGS waveforms

SF.40.14.B1115: Blind and Beacon-Less TDMA Scheduling for Ad-Hoc LEO Satellite Communications

Pham, K - (505) 846-4823

Future satellite missions require radio frequency (RF) subsystem architectures with low size, weight, and power (SWAP) that can support remotely piloted aircraft (RPA)’s high data rates at the order of Gbps for both uplinks and downlinks. To meet the ever increasing demands of high data rates, the most commonly used technology in RPA communications is often to be dual polarization in conjunction with time division multiple access (TDMA) and a constellation of Low-Earth-Orbiting (LEO) satellites. Currently, the TDMA technique for LEO satellites requires satellite radio beacons (or pilot tones) to perform TDMA scheduling. Any satellite payloads, which require space radio beacon systems, will increase the SWAP requirements. In this opportunity the Air Force is soliciting innovative R&D advances to enable future technology capabilities in the following aspects: (1) revolutionary design principles using TDMA scheduling without space or satellite radio beacons, (2) robust analysis on satellite fingerprints to search for satellite identification and availability, (3) on/off-board TDMA scheduling to efficiently disseminate schedules to RPA platforms, and (4) TDMA scheduling techniques with and without requiring a priori knowledge of satellite locations. The introduction of this emerging capability onto satellite platforms should have minimal impacts on SWAP requirements and require no a-priori knowledge of satellite locations. References: Nguyen TM: Plenary Paper, SPIE Defense and Security 2013: Sensors and Systems for Space Applications VI, Proceedings of SPIE, Vol. 8385: Baltimore, MD, 2013 Kwan WC, Sieteng S, Chen M: A Novel Spatial TDMA Scheduler for Concurrent Transmit/Receive Wireless Mesh Networks, 24th IEEE International Conference on Advanced Information Networking and Applications: 2010 Keywords: Satellite radio beacons; Feature extraction and inference; Satellite fingerprints; Spoofing and jamming; TDMA scheduling; Sparse observations; SWAP Eligibility: Open to U.S. citizens Only

SF.40.14.B1112: Game-Theoretic Based Decision Support Tools for Persistent Space Threat Interdiction

Pham, K - (505) 846-4823

Today the US has a tremendous investment in space, especially in military, intelligence, scientific, and commercial sectors. However, one of the most important space vulnerabilities is the lack of persistent situation awareness of the space operational environment to ensure freedom of action. Space can be an important battlefield in modern warfare because intelligence information from space has become extremely vital for strategic decisions. In addition to real-time and hidden information constraints, the presence of adversaries greatly complicates the decision making process. It becomes necessary to perform space defense analysis and mission trade studies. Although pursuit-evasion game theory is relevant to this problem, most results in the existing literature are from the pursuers’ perspective and not applicable. Innovative solutions are sought for (1) proper game models and constructive game training for a generic space defending scenario where multiple denying assets, defending assets, and pursuing assets with either equal or unequal capabilities are assumed with imperfect, sporadic observations and jamming confrontations; (2) possible constructive methods and approximate solution techniques on distributed learning under sparse communications and adverse environments; (3) efficient computational algorithms to determine real-time cooperative strategies for the space assets, neutral objects, and threats in persistent area denial; and (4) assess the performance under technical failure inaccurate measurements and loss of communications. Proposed advances--together with potential deliverables including novel mathematical developments, interaction modeling, performance metrics, advanced engagement concepts, and design principles--set the foundations to enable assured operations of teams of autonomous defense systems to adapt to hostile, nontraditional environments, which capitalize on effective utilization of modeling and analysis of uncertain systems, as well as multilevel, multi group, multi-agent, control and decision analysis. References: Shen D, Pham KD, et al: “Pursuit Evasion Orbital Game for Satellite Interception and Collision Avoidance,” SPIE Defense and Security 2011: Sensors and Systems for Space Applications IV, Proceedings of SPIE 8044: Orlando, FL, 2011 Pham KD: “Risk-Averse Based Paradigms for Uncertainty Forecast and Management in Differential Games of Persistent Disruptions and Denials,” Proceedings of American Control Conference: 842, Baltimore, MD, 2010 Keywords: Active and distributed learning; Modeling of complex systems; Competitive decision making; Adversarial systems; Distributed computation; Multilevel command and control in hostile environment Eligibility: Open to U.S. citizens Only

SF.40.12.B8192: SSA Characterization

Milster, S.P. - 505.846.7752

We seek an Associate for a position in Space Situational Awareness (SSA) Characterization. The work will involve merging photometric (visible and near IR) observations with novel approaches at detector and orbital dynamics characterizations. Experience has shown that the photometric state of a Resident Space Object (RSO) is directly related to its physical state. Advances in SSA characterization will likely come from pushing the algorithms that measure raw data, extract orbital motion information, and extract information about the photometric state. The successful candidate would have expertise and/or interests in observational photometry, calibrations, faint object detection, orbital mechanics, and algorithm development. References Ferguson DC, et al: Journal of Spacecraft and Rockets 51(6): 1907-1913, 2014 Skinner M, et al: Commercial Space Situational Awareness–An investigation of ground-based SSA concepts to support commercial GEO satellite operators, in Advanced Maui Optical and Space Surveillance Technologies Conference (Volume 1, page 9) September 2013 Skinner MA, et al: Acta Astronautica 105(1): 1-10, 2014 Keywords: SSA; Space; Situational awareness; Photometry; Characterization; Satellite; Visible; near IR; Eligibility: Open to U.S. citizens Only

SF.40.12.B8174: Passive Optical Remote Sensing and Imaging of Manmade Objects in Geosynchronous Earth Orbit

Crabtree, P.N. - 505.846.0437

Our research centers on techniques for passive optical remote sensing and imaging of manmade objects in geosynchronous Earth orbit (GEO). Resolved imaging of GEO satellites continues to be a challenging problem due their great distance from both ground-based locations and low Earth orbit (LEO). We are currently interested in (1) both data processing techniques and optical designs to maximize the imaging performance of space-borne cameras and (2) more exotic synthetic aperture techniques, such as shadow imaging based on measurements of the Fresnel diffraction pattern of the object silhouette during stellar occultation. Interferometry techniques are also of interest, but since they face immense technical and engineering challenges, the simpler measurement process of shadow imaging is currently of greater interest. Image processing codes and techniques developed may be applied to data captured by AFRL space experiments. Synthetic aperture techniques are studied by analysis and simulation; results will guide future imaging architectures and experiments aimed at improved characterization of space objects. Keywords: Remote sensing; Synthetic aperture; Shadow imaging; Multiframe image enhancement; Image registration; Optical flow; Stellar occultation; Super-resolution; High dynamic range; Eligibility: Open to U.S. citizens Only

SF.40.12.B8031: Energetic Particle Dtection, Data Analysis, and Modeling for Radiation Belt Studies

Selensnick, R - (505) 846-5358

There is a need for improved methods for discriminating nuclear explosions from earthquakes and other natural and man-made seismic sources, and characterizing suspicious seismic sources. The technical challenges are driven by the need to monitor smaller events. Recordings of smaller events are generally sparser, made at closer distances (local and near regional), have lower signal-to-noise ratios, and have maximum signal amplitudes at higher frequencies than recordings of larger events. These differences all present challenges. Of the two most effective discriminants, phase ratio discriminants can fail at local distances and in areas with high attenuation, while the Ms:mb discriminant may not work for small shallow events (Stevens and Day, 1985). In addition, monitoring requirements evolve in response to geopolitical events, which drives a need to monitor in new regions that are often poorly calibrated both empirically and with respect to the resolution of available Earth models. The need to use higher frequency and lower signal-to-noise ratio waveforms for smaller events exacerbates the problems that arise from insufficient Earth model resolution. This drives a need for discriminants that are robust to high attenuation and limited means for removing propagation effects from seismic waveforms. These requirements drive a need for extensions of existing discriminants to make them more effective for the challenging monitoring conditions described above, and for new discriminants that are effective for small events recorded sparsely at local and near regional distances. New methods will require a firm physical basis to support their application in new areas. Inversion for regional moment tensors is currently an effective automated means (e.g. Ekström et al., 2012) of identifying earthquake focal mechanisms and for separating populations of different events types (Ford et al., 2009) at regional distances. Statistically rigorous uncertainty estimates however are needed, as are methods to improve resolution for smaller events, for which propagation effects are more difficult to predict and remove for the higher frequency waveforms. Methods such as the inclusion of specific parametric measurements as a priori constraints to moment tensor inversion (Ford et al., 2012) and phase matched filtering to enhance signal-to-noise (unpublished work at AFRL) have been effective approaches that merit further development and application. Further development and application of such methods are sought. References: Stevens J.L. and S. Day (1985), “The physical basis of mb:Ms and variable frequency magnitude methods for earthquake/explosion discrimination”, Jour. Geophys. Res, 90, B4, DOI: 10.1029/JB090iB04p03009 Ekström, G., M. Nettles, and A. M. Dziewonski (2012), “The global CMT project 2004-2010: Centroid-moment tensors for 13,017 earthquakes”, Phys. Earth Planet. Inter., 200-201, 1-9, 2012. doi:10.1016/j.pepi.2012.04.002 Ford., S. R., W. R. Walter and D. S. Dreger (2012), “Event discrimination using regional moment tensors with teleseismic-P constraints”, Bull. Seism. Soc Am., 102, 867-872, doi:10.1785/0120110227, 2012 Ford, S.R., D.S. Dreger, and W.R. Walter (2009), “Identifying isotropic events using a regional moment tensor inversion”, J. Geophys. Res., B01306, doi:10.1029/2008JB005743, 2009 Keywords: Seismology; Explosion; Earthquake; Moment Tensor ; Phase Matched Filter; Discrimination Eligibility: Open to U.S. citizens Only Level: Open to Regular and Senior applicants

SF.40.12.B8021: Investigations into the vertical structure of Traveling Ionospheric Disturbance, their assimilation into ionospheric models, and their impacts on RF Propagation

Colman, J - (505) 846-3172

The specification of ionospheric characteristics has a major impact on the operation of many important remote sensing and communication systems. The utility of climatological models in capturing the large scale features of the ionosphere, such as bulk seasonal or diurnal variations, is clear. More recently assimilative models of the ionosphere have been used extensively in this context and provide better real time or hindcast capabilities. It is now well known that beyond the large scale features of the ionosphere there exists a hierarchy of transient perturbations, some of which appear as coherent wave structures. The advent of high spatial density networks of GPS receivers, from which the total electron content (TEC) between the satellite and receiver can be determined, has made the observation such structures in TEC maps almost routine. Such wave structures have also been observed in many other ionospheric observational platforms such as all sky optical imager, Ionosonde, Incoherent Scatter Radar (ISR), and HF Doppler sounders. While there have been a few studies comparing the phenomenology of the different observational systems an integrated understanding of these features is still lacking. Historically such coherent wave structures have been deemed Traveling Ionospheric Disturbances (TID). Such ionospheric disturbances are thought to originate from similar disturbances in the neutral atmosphere often called Traveling Atmospheric Disturbances (TAD). TIDs have typically been categorized into large scale (LSTID) and medium scale (MSTID). In general LSTIDs propagate quasi-horizontally with phase velocities in the 400-600 m/s range and wavelengths of 1000 km or more. They are associated with step changes to Joule heating in the auroral zone and have a strong correlation to the AE index. MSTIDs may have a vertical component to their propagation with phase velocities of 100-200 m/s and wavelengths of a few hundred kilometers. Their origins are typically described as stratospheric or below, e.g. orographic wind, convective systems, earthquakes, tsunamis. Their occurrence rates are still under investigation and range from a few percent to ubiquitous. Some of this disagreement stems from the different definitions and observational systems used to construct the climatologies. There are even smaller irregularities, traveling and otherwise and all of these structures coexist creating complex structures. Interpretation of such measurement prior to assimilation into a model requires some knowledge or assumptions about ionospheric structures, e.g. conversion of slant TEC into vertical TEC or performing an Abel transform on Radio Occultation data. Such interpretation can be complicated by the presence of TIDs and depends in part on the spatial or temporal characteristics of the measurement. At AFRL we have recently executed, and have planned, a number of field experiments where multiple ionospheric measurement devices have been fielded together including: multiple Digisondes, all-sky imagers, a Fabre Perot Interferometer, Radio Beacon Receivers, HF spectrum analyzers, and GPS receivers. The Digisondes were often run at relatively high cadence and in oblique, or otherwise coordinated, modes. The proper multi-phenomenological interpretation of these data sets in terms of TIDs and TADs is of great interest for an improved understanding of their sources, vertical structure, and propagation characteristics as well as developing methods to understand their impact on assimilative models (or to assimilate them directly as coherent structures) and thereby their impact on RF propagation. References M. A. Cervera and T. J. Harris (2014) Modeling ionospheric disturbance features in quasi-vertically incident ionograms using 3-D magnetoionic ray tracing and atmospheric gravity waves, J. Geophys. Res., 119, 431-440, doi:10.1002/2013JA019247 R. Leitinger and M. Rieger (2005) The TID model for modulation of large scale electron density models, Ann. Geopys., 48, 3, 515-523 D. J. Livneh, I. Seker, F. T. Djuth, and J. D. Mathews, Omnipresent vertically coherent fluctuations in the ionosphere with a possible worldwide-midlatitude extent (2009), J. Geophys, Res., 114, doi:10.1029/2008JA013999 McNamara, L. F., C. R. Baker, and W. S. Borer (2009), Real-time specification of HF propagation support based on a global assimilative model of the ionosphere, Radio Sci., 44, RS0A15, doi:10.1029/2008RS004004 McNamara, L. F., M. J. Angling, S. Elvidge, S. V. Fridman, M. A. Hausman, L. J. Nickisch, and L.-A. McKinnell (2013), Assimilation procedures for updating ionospheric profiles below the F2 peak, Radio Sci., 48, doi:10.1002/rds.20020 T. Ogawa, N. Balan, Y. Otsuka, K. Shiokawa, C. Ihara, T. Shimomai, and A. Saito (2002), Observations and modeling of 630 nm airglow and total electron content associated with traveling ionospheric disturbances over Shigaraki, Japan, Earth Planets Space, 54, 45-56 T. Tsugawa, Y. Otsuka, A. J. Coster, and A. Saito (2007), Medium-scale traveling ionospheric disturbances detected with dense and wide TEC maps over North America, Geophys. Res. Lett., 34, doi:10.1029/2007GL031663 >Keywords Ionosphere; HF Propagation ; Traveling Ionospheric Disturbance; Digisonde; GPS; Assimilative Modeling; TEC; Vertical Structures; System Impacts Eligibility: Open to U.S. citizens Only Level: Open to Regular and Senior applicants

SF.40.12.B8020: Development of Methods for Local and Near Regional Seismic Event Discrimination and Characterization

Baker, G - (505) 846-6070

There is a need for improved methods for discriminating nuclear explosions from earthquakes and other natural and man-made seismic sources, and characterizing suspicious seismic sources. The technical challenges are driven by the need to monitor smaller events. Recordings of smaller events are generally sparser, made at closer distances (local and near regional), have lower signal-to-noise ratios, and have maximum signal amplitudes at higher frequencies than recordings of larger events. These differences all present challenges. Of the two most effective discriminants, phase ratio discriminants can fail at local distances and in areas with high attenuation, while the Ms:mb discriminant may not work for small shallow events (Stevens and Day, 1985). In addition, monitoring requirements evolve in response to geopolitical events, which drives a need to monitor in new regions that are often poorly calibrated both empirically and with respect to the resolution of available Earth models. The need to use higher frequency and lower signal-to-noise ratio waveforms for smaller events exacerbates the problems that arise from insufficient Earth model resolution. This drives a need for discriminants that are robust to high attenuation and limited means for removing propagation effects from seismic waveforms. These requirements drive a need for extensions of existing discriminants to make them more effective for the challenging monitoring conditions described above, and for new discriminants that are effective for small events recorded sparsely at local and near regional distances. New methods will require a firm physical basis to support their application in new areas. Inversion for regional moment tensors is currently an effective automated means (e.g. Ekström et al., 2012) of identifying earthquake focal mechanisms and for separating populations of different events types (Ford et al., 2009) at regional distances. Statistically rigorous uncertainty estimates however are needed, as are methods to improve resolution for smaller events, for which propagation effects are more difficult to predict and remove for the higher frequency waveforms. Methods such as the inclusion of specific parametric measurements as a priori constraints to moment tensor inversion (Ford et al., 2012) and phase matched filtering to enhance signal-to-noise (unpublished work at AFRL) have been effective approaches that merit further development and application. Further development and application of such methods are sought. References >Stevens J.L. and S. Day (1985), “The physical basis of mb:Ms and variable frequency magnitude methods for earthquake/explosion discrimination”, Jour. Geophys. Res, 90, B4, DOI: 10.1029/JB090iB04p03009 >Ekström, G., M. Nettles, and A. M. Dziewonski (2012), “The global CMT project 2004-2010: Centroid-moment tensors for 13,017 earthquakes”, Phys. Earth Planet. Inter., 200-201, 1-9, 2012. doi:10.1016/j.pepi.2012.04.002 >Ford., S. R., W. R. Walter and D. S. Dreger (2012), “Evendiscrimination using regional moment tensors with teleseismic-P constraints”, Bull. Seism. Soc Am., 102, 867-872, doi:10.1785/0120110227, 2012 >Ford, S.R., D.S. Dreger, and W.R. Walter (2009), “Identifying isotropic events using a regional moment tensor inversion”, J. Geophys. Res., B01306, doi:10.1029/2008JB005743, 2009 Keywords: Seismology; Explosion; Earthquake; Moment Tensor ; Phase Matched Filter; Discrimination Eligibility: Open to U.S. citizens Only Level: Open to Regular and Senior applicants

SF.40.12.B7987: Cold-Atom Precision Timing and Inhertial Navigation

Olson, S - (505) 846-4799

The subject of our research is precision timing and inertial sensing enabled by laser-cooling, trapping, and advances in photonics. One of our major efforts pursues the development of robust, miniaturized optical clocks and associated frequency combs in order to develop a cost-effective replacement for the atomic clocks aboard the global positioning satellite constellation. Another major effort uses atom-chip devices to develop confined atom interferometry. Confined interferometry offers the possibility to dramatically increase interrogation time of atom-based inertial sensing devices. We use a rapid prototyping technique for atom chips that allows us to quickly customize and live-test atom chip structures. We are also exploring techniques for developing compact atomic-devices, including large-diameter hollow-core fiber guiding and integrated atom-chip transport. More recently, we have begun investigating the development of atom-chip-based continuously replenished (CR) Bose-Einstein condensate (BEC). A CR BEC will be the leading steps into achieving a truly continuous-wave atom laser. Keywords: Quantum enhanced scattering; Atomic clock; Ultracold atoms; Bose-Einstein condensate; Frequency comb; Atom laser; Hollow-core fiber atom guiding; Atom chips; Atom interferometry Eligibility: Open to U.S. citizens Only Level: Open to Regular and Senior applicants

SF.40.10.B8178: Advanced Satellite Navigation Technologies

Naudeau, Madeleine - (505)853-7107

Research Program Abstract/Content. Also, specify any security/citizenship constraints/requirements needed in order to participate in the Research Program/Topic
The Advanced Satellite Navigation (SatNav) Technologies (AST) program researches architectures and technologies for providing SatNav signals to users around the globe and in space. Research areas include: advanced signals, spacecraft payloads, and SatNav control systems. Technology areas include: digital and RF signal processing, software defined radios, RF signal generation and broadcast payload hardware, encryption, and command and control technologies. The AST program is developing signals for the next generation SatNav systems, including GPS. These signals will close weaknesses in existing GPS signals, such as provide authentication of civilian signals, rapid acquisition of military signals, improved performance of military signals in jamming situations, etc. Research is ongoing both in the development of new signal and the receiver algorithms necessary to fully utilize the advanced signal features. The program also develops the payload technology needed to broadcast these SatNav signals and the control segment to monitor and command the spacecraft to broadcast the signals with high accuracy.

SF.40.09.B7485: Laser Spectroscopy of Next-Generation Propellants

Annesley, Christopher - (505) 846-1042

Our research centers on the chemistry of space vehicles: the reactions involved in hypergolic ignition and the subsequent interactions between the thruster plume and the near-space environment. We are currently interested in the spectroscopy, structure, and reactivity of novel ionic liquid propellants, which are being pursued as a next-generation, “green” alternative to the toxic hydrazine-based systems currently in use. Ultraviolet spectroscopy of gas-phase ionic liquid ion pairs in a supersonic jet provides optical signatures of these new compounds. Infrared spectroscopy identifies distinctive molecular vibrations, which are compared to vibrational frequencies calculated using standard computational chemistry methods. This comparison allows us to determine the ion pair structures present in the experiment, as well as to rigorously test the methods of theory employed. We are also developing an instrument which will use electrospray to transfer clusters of ionic liquids into the gas phase, where they will be stored in a cold ion trap for studies of their spectroscopy and hypergolic reactions.
Keywords:Lasers; Spectroscopy; Mass spectrometry; Propulsion; Computational chemistry; Spacecraft;

SF.40.07.B5822: Seismic and Infrasound Research for Monitoring Nuclear Explosions

Baker, Harold - (505) 948-0027

Underground nuclear explosions generate seismic and infrasound waves. Monitoring underground explosions encompasses a wide range of seismic and acoustic disciplines. The source mechanics must be understood in terms of the amount and type of seismic and infrasound radiation produced-not only by underground nuclear explosions, but also by other sources such as small shallow earthquakes and industrial explosions. The effects of propagation (including attenuation) through the solid Earth or atmospheric medium control the travel time, amplitude, and other characteristics of waves measured at a seismometer or microbarograph. These basic problems control the ability to perform the practical procedures of detection and location of an event, identification of the event as a nuclear explosion or some other type of source, and estimation of the yield if it is an explosion. Methods of tackling the research problem include theoretical investigation of source physics, modeling and simulation of seismograms and microbarograms to better understand both source and propagation processes, and observational studies of seismic and acoustic wave characteristics and Earth/atmosphere models. We are particularly interested in studies of relatively small (magnitude <4) shallow seismic sources and propagation at local (<200 km) and regional (<3,000 km) distances. Keywords: Seismic; Seismic sources; Seismic wave propagation; Infrasound; Infrasound sources; Infrasound propagation; Underground nuclear explosions; Nuclear explosion monitoring; Earth models Eligibility: Open to U.S. citizens Only

SF.40.07.B5812: Diagnostics and Modeling of Active Ionospheric Experiments

Pedersen, T.R - (505) 853-3792

Active ionospheric experiments, where perturbations to the ionosphere are created via addition of energy and/or injected constituents, have great potential for aiding understanding of the processes that occur in the ionospheric plasma and upper atmospheric gas, especially for conditions outside the range typical of day-to-day natural variability. However, to fully realize this potential, diagnostics and modeling capable of reconstructing and reproducing the phenomena and processes in the perturbed region are essential. RF, optical, in-situ, and other diagnostics techniques to better specify the composition and densities in the region as a function of time, as well as models capable of ingesting these measurements and recreating the observed effects are all areas where further work is needed. In particular, many of the assumptions employed in studies of the natural background ionosphere and upper atmosphere, such as large scale sizes compared to the wavelength of the probing waves, or prevalence of ground states over excited states, break down when applied to localized discrete perturbations, especially at early times when the affected area can be very small. Additional features of interest include stability of gradients and development of irregularities, as well as motion and evolution of the perturbed regions in response to plasma and neutral motions in the background. Models of these processes have been developed, but are poorly constrained by the observational data, especially at early times when the perturbation is too intense and too small for standard measurement techniques to succeed. This topic focuses on development of better observation and modeling techniques to fill these gaps and improve our understanding of processes in the ionosphere and upper atmosphere. Our group maintains a large data set of measurements of active experiments, to include RF heating experiments and a variety of chemical releases, as well as close collaborations with a number of theorists and modelers.
References:
Ober, D. M., Crawford, T. S., Eccles, J.V., & Holmes, J. M. (2021). 3D multi-fluid MHD simulation of the early time behavior of an artificial plasma cloud in the bottom side ionosphere. Journal of Geophysical Research: Space Physics, 126, e2020JA029036. https://doi.org/10.1029/2020JA029036
Haerendel, Gerhard et al. (2019), Experiments With Plasmas Artificially Injected Into Near-Earth Space, Frontiers in Astronomy and Space Sciences, Vol. 6. DOI=10.3389/fspas.2019.00029 https://www.frontiersin.org/article/10.3389/fspas.2019.00029
Pedersen, T. R., Caton, R. G., Miller, D., Holmes, J. M., Groves, K. M., and Sutton, E. (2017), Empirical modeling of plasma clouds produced by the Metal Oxide Space Clouds experiment, Radio Sci., 52, 578– 596, doi:10.1002/2016RS006079.
Pedersen, T., Gustavsson, B., Mishin, E., Kendall, E., Mills, T., Carlson, H. C., and Snyder, A. L. (2010), Creation of artificial ionospheric layers using high-power HF waves, Geophys. Res. Lett., 37, L02106, doi:10.1029/2009GL041895.

Open to US Citizens Only

SF.40.07.B5380: Space Weather and Effects

Mozer, J.B - (505) 853-0059

This research opportunity addresses problems related to solar and heliospheric disturbances that affect DOD operations, including satellites, communication, and navigation systems. Research topics exist in the study of solar flares, solar energetic particles, coronals mass ejections, and shocks in the solar wind, with particular emphasis on detection, forecasting, and modeling of impacts on the geospace environment. Solar telescope facilities, including high spatial, temporal, and spectral resolution observations of the Sun are available on site, as well as access to data from satellites, such as AFRL's Solar Mass Ejection Imager (SMEI).

SF.40.07.B0179: Advanced Space-Based Imaging

Lipson, S.J - (505) 853-3531

We develop and exploit multiple technologies for space-based optical and infrared detection and identification, with an emphasis on advanced imaging sensor payloads. Possible research topics include imagery data analysis, object identification algorithms, signal processing, satellite on-board processing, data compression, time-series analysis, sensor calibration, modeling of atmospheric transmission and compensation, and other topics related to space-based remote sensing, object identification, and payload design. We have facilities for algorithm development, modeling and simulation, and an in-house sensor calibration facility.

SF.40.06.B0170: Plasma Chemistry for Space Applications

Viggiano, A.A - (505) 853-3399

We study a broad range of plasma chemistry including electron attachment, ion-molecule reactions, dissociative recombination, and mutual neutralization. We specialize in studying difficult species, radicals, and extended temperature ranges. Several fast flow plasma reaction apparatuses are used. The ion-molecule temperature range is 90-1800 K, while for the other plasma processes temperatures up to 1400 K can be studied. Recent successes include measuring the only product distributions for mutual neutralization, electron attachment to fluorocarbon radicals, and the discovery that electrons catalyze mutual neutralization. A recent upgrade has allowed for studies of radicals with electrosprayed ions, which is important for solar fuels research.

The data support a wide variety of AF/DoD applications including the natural ionosphere, hypersonic vehicles, plasmas assisted combustion, high power lasers, conversion of gaseous to liquid fuels, trace gas detection, high energy density materials, and other catalytic processes.

SF.40.04.B8143: Nonlinear Plasma Processes in the Subauroral Geospace Weather

Mishin, E.V. - 505.846.7227

The subauroral ionosphere lays just equatorward of the auroral boundary. It maps along magnetic field lines into the inner magnetosphere, which includes the ring current (RC), innermost part of the outer radiation belt (RB), and plasmasphere adjacent to the electron plasma sheet (PS) boundary. For brevity, we call this ionosphere-magnetosphere region the subauroral geospace. The quiet time convection in the subauroral geospace is virtually featureless. During (sub)storms, latitudinally narrow jets of subauroral westward convection, subauroral ion drifts (SAID), emerge in the pre-midnight sector, while broad westward flows, subauroral polarization streams (SAPS), appear in the duskside. Just after the substorm onset, SAPS are highly structured and termed SAPSWS (wave structures). SAPSWS co-locate with RB and RC particle precipitation, radar clutter, and UHF/GPS scintillations. Though the development of SAID/SAPS and related space weather effects have been under investigation for decades, the understanding of the underlying physics, especially rapidly developing intense features near substorm onsets, is still lacking. It is generally implied that poleward electric fields Es driving SAID and SAPS develop due to similar, if not the same, mechanisms, known as voltage and current generators. The former places SAID/SAPS between the inner boundaries of =1-keV ion and electron convection defined by the E×B and gradient-curvature drifts. The latter explores closure of the Region 2 field-aligned currents (FACs) through a low-conductive ionosphere, resulting in locally enhanced poleward electric field. The generator concept is based on the test (single) particle approach and has come to be called the SAID/SAPS paradigm. However, recent studies show that the paradigm is in serious error. One of the most striking discrepancies is that the paradigm predicts the timescale of a few hours, while substorm subauroral events appear in ~10 min or less. The fast timescale and SAID’s MLT sector are characteristic of the propagation of substorm injections (hot plasma jets). Therefore, we develop a concept of the SAID channel as an integral part of a turbulent plasmaspheric boundary layer (TPBL). TPBL forms in the evening sector where the plasmasphere short-circuits reconnection-injected plasma jets. However, we still know little about the underlying mechanism of SAPS, particularly SAPS wave structures (SAPSWS), except that nonlinear plasma effects are critical. Transient SAPS enhancements also appear at times well separated from substorm onsets and correlate with auroral streamers, the footprint of mesoscale plasma jets in the magnetotail. These observations hint at a common process underlying the SAPS/SAPSWS generation and the over-arching problem of transport of reconnection-created jets toward the Earth. The required level of understanding of basic plasma processes that control the spatiotemporal development of the perturbed subauroral geospace can only be achieved using a multidisciplinary effort utilizing experimental, theoretical, and numerical investigations. Reference: Basu S, et al: Journal of Geophysical Research 113: A00A06, doi:10.1029/2008JA013076, 2008 Makarevich R, et al: A. Kellerman, Journal of Geophysical Research 116: A11311, 2011 Mishin E, Puhl-Quinn P, Santolik O: Geophysical Research Letters 37: L07106, doi:10.1029/2010GL042929, 2010 Mishin E, Albert J, Santolik O: Geophysical Research Letters 38: L21101, doi:10.1029/2011GL049613, 2011 Mishin E: Journal of Geophysical Research 118: 5782, doi:10.1002/jgra.50548, 2013 Keywords: Space weather; Subauroral geospace; SAPS/SAID; Plasmaspheric boundary layer; Substorm injection; Ring current injection; Radiation belt boundary; Eligibility: Open to U.S. citizens Only

SF.40.04.B0207: Research and in Electro-Optical Sensors for Use in Space

Cardimona, David - 505-846-5807

Research opportunities in the Advanced Detectors Research Group of the Space Vehicles Directorate are extremely varied. Experimental and theoretical research focuses on new detector development in the visible to mm-wave wavelength range (currently specializing in infrared [IR]); new detector capabilities such as wavelength tunability and polarization discrimination; and detector interactions with external electric, magnetic, and electromagnetic fields. We are currently concentrating on III-V semiconductor multiple quantum well, superlattice, quantum wire, and quantum dot heterostructures. We have begun investigating the possibilities of plasmonic enhancement for IR detection. Our main emphasis is on space-based applications of these new detector designs, so we will always be concerned with radiation hardness and high sensitivity in our studies. We mainly investigate single detector pixels, but we are also interested in full focal plane arrays. Our current research interests include (1) optical-spectroscopy studies such as absorption, photoluminescence, light scattering, and ultra-fast pump/probe transient spectra; and (2) quantum-transport studies such as tunneling, drift, diffusion, and field domains. Available characterization equipment include Fourier-transform IR spectroscopy, magneto-transport and magneto-optical, deep level transient spectroscopy, femtosecond laser pump/probe, and all the equipment necessary to fully characterize detector dynamics and performance at cryogenic temperatures. We have extensive collaborations with universities around the country, especially the University of New Mexico, as well as with Sandia National Lab`s CINT facility where we can obtain access to MBE machines, clean rooms, SEMs, and AFMs.
Eligibility: Open to U.S. citizens Only

SF.40.04.B0205: Infrared and Visible Detectors

Huang, D. - 505-846-5788

We perform theoretical and experimental research on infrared detectors made of HgCdTe, and superlattice (SL) IR detectors made of II-VI and III-V material systems, such as HgTe/CdTe and InAs/InGaSb. We investigate the band structure, absorption coefficient, quantum efficiency, dark current etc of these materials and detectors.We are currently studying the following topics: p-type doping in HgCdTe, alternate substrates for HgCdTe and SL detectors, methods to decrease dark current and increase uniformity, increase operating temperature etc. There is also interest in Si hybrid visible detectors. Available laboratory equipment include Fourier-transform IR spectroscopy, and all the equipment necessary to fully characterize detector performance from room temperature to cryogenic temperatures. We collaborate with the University of Illinois, North Western University, and Army Research Laboratory. References: Yong Chang, Christoph H. Grein, Sivalingam Sivananthan, M.E. Flatte, V. Nathan, and S. Guha, ""Narrow Gap HgCdTe Absorption behavior near the Band Edge including Nonparabolicity and the Urbach Tail,"" Appl. Phys. Lett. 89, 062109 (2006); Binh-Minh Nguyen, Darin Hoffman, Pierre-Yves Delaunay, Manijeh Razeghi, and Vaidya Nathan, ""Polarity inversion of type II InAs/GaSb superlattice photodiodes,"" App. Phys. Lett. 91, 103503(2007); Andrew Hood, Pierre-Yves Delaunay, Darin Hoffman, Binh-Minh Nguyen, Yajun Wei, Manijeh Razeghi and Vaidya Nathan, ""Near bulk-limited R0A of long-wavelength infrared type-II InAs/GaSb superlattice photodiodes with polyimide surface passivation,"" Appl. Phys. Lett. 90, 233513 (2007). Eligibility: Open to U.S. citizens Only

SF.40.04.B0205: Electron Dynamics and Performance Issues in Infrared and Visible Detectors

Huang, D. - 505.846.5788

We perform theoretical and experimental research on infrared detectors made of HgCdTe, and superlattice (SL) IR detectors made of II-VI and III-V material systems, such as HgTe/CdTe and InAs/InGaSb. We investigate the band structure, absorption coefficient, quantum efficiency, dark current etc of these materials and detectors.We are currently studying the following topics: p-type doping in HgCdTe, alternate substrates for HgCdTe and SL detectors, methods to decrease dark current and increase uniformity, increase operating temperature etc. There is also interest in Si hybrid visible detectors. Available laboratory equipment include Fourier-transform IR spectroscopy, and all the equipment necessary to fully characterize detector performance from room temperature to cryogenic temperatures. We collaborate with the University of Illinois, North Western University, and Army Research Laboratory. References: Yong Chang, Christoph H. Grein, Sivalingam Sivananthan, M.E. Flatte, V. Nathan, and S. Guha, ""Narrow Gap HgCdTe Absorption behavior near the Band Edge including Nonparabolicity and the Urbach Tail,"" Appl. Phys. Lett. 89, 062109 (2006); Binh-Minh Nguyen, Darin Hoffman, Pierre-Yves Delaunay, Manijeh Razeghi, and Vaidya Nathan, ""Polarity inversion of type II InAs/GaSb superlattice photodiodes,"" App. Phys. Lett. 91, 103503(2007); Andrew Hood, Pierre-Yves Delaunay, Darin Hoffman, Binh-Minh Nguyen, Yajun Wei, Manijeh Razeghi and Vaidya Nathan, ""Near bulk-limited R0A of long-wavelength infrared type-II InAs/GaSb superlattice photodiodes with polyimide surface passivation,"" Appl. Phys. Lett. 90, 233513 (2007). Eligibility: Open to U.S. citizens Only

SF.40.02.B0183: Plasma Spacecraft Interactions

Cooke, D.L - (505) 846-6150

We conduct numerous studies of spacecraft-space plasma interactions that include theory, experiment, data analysis, and computer modeling. This opportunity will emphasize computer modeling in conjunction with ongoing space and laboratory experiments. Possible research topics include critical velocity ionization phenomenon; ionization and discharge processes; optical remote sensing; neutral and ionized gas interactions with ambient medium, high-voltage systems; and natural and induced spacecraft charging. We maintain facilities for computing and scientific visualization, as well as a convenient supercomputer access.

SF.40.02.B0180: Solar-Terrestrial Physics

Kahler, S - (505) 853-3517

We conduct research on the characterization, understanding, and prediction of the key elements of space environmental disturbances. These include coronal mass ejections, high-speed solar wind streams, solar energetic particle events, and geomagnetic storms. Current research emphasizes particle acceleration and propagation from the Sun to 1 AU, solar and interplanetary sources of transient and recurrent geomagnetic storms, and periodicities (e.g., semiannual, 22 year) in geomagnetic activity. This work is based on various kinds of ground- and space-based data. We welcome proposals on interdisciplinary efforts that cross boundaries of the Sun, solar wind, and magnetosphere. Keywords: Solar corona; Solar wind; Solar energetic particle events; Solar storms; Eligibility: Open to U.S. citizens Only Level: Open to Regular and Senior applicants

SF.40.01.B8159: Comprehensive Experimental and Theoretical Investigation of Electron and Hole Transport Properties

Sharma, A.K. - 505.846.0165

In the nanoscale-regime, the electrons and other quasi-particles, such as holes and excitons, start to behave more like waves than particles. This transition into the quantum mechanical regime does not come about abruptly. Rather, there is a transition region in which bulk properties begin to slowly weaken while the quantum mechanical effects begin to strengthen. However, the effects of quantum confinement on carrier transport properties have been primarily investigated in ternary and quaternary material heterostructures and superlattices, in which scattering is seen to enhance some modes of electron-lattice interaction while suppressing others, thereby changing the relative value of the carrier’s effective masses of electrons and holes, as compared to bulk semiconductors. Studies of quantum confinement and transport in Si and GexSi(1-x) have been very limited. However, as Si based and GexSi(1-x) based active regions of the microelectronic devices are scaled down in all three dimensions to a few nanometers, understanding of the physics, especially electron-hole transport properties, including the role of biaxial strain, in the transition region is of great importance, particularly as it affects the overall band structure. Therefore, carrier-lattice interactions (i.e., strain effects), which includes the reversal splitting of light- and heavy-hole bands, as well as the decrease of conduction-band effective mass by reduced semiconductor bandgap energy to the extent of splitting the valence-band’s relative positions of heavy holes and light holes, as compared to bulk Si and GexSi(1-x), in turn has a direct effect on both electron and hole mobilities, thus the speed and high frequency response of the devices. References:Ghatak BKP: Effective Electron Mass in Low-Dimensional Semiconductors. New York: Springer, 2013: 978-3-642-31247-2/0933-033X Ohta H, Watanabe T, Ohdomari I: Japanese Journal of Applied Physics 46(5B): 3277-3282, 2007 Keywords: Semiconductor growth; Semiconductor junctions; Lattice mismatch; Interfacial strain; Nanowires; Nanoscaled devices; Nanoelectronics; Semiconductor physics; Semiconductor fabrication; Eligibility: Open to U.S. citizens Only

SF.40.01.B7633: Ionosphere/Magnetosphere Modeling of Wave Propagation or Wave-Particle Interaction

Su, Y-J.C - (505) 846-7845

This opportunity encourages applicants to develop new methods or adopt existing models to study wave propagation or wave-particle interaction in the ionosphere-magnetosphere system. Research topics range from electromagnetic signals interrupted by ionospheric density irregularities (i.e., scintillation) to wave-particle interaction scattering energetic particles in the inner magnetosphere. Associates will be encouraged to develop their own research efforts making progress toward improved space weather predictions. We anticipate results from this numerical work will be directly driven by, compared to, and/or validated by ground or satellite measurements. Keywords: Ionosphere; Magnetosphere; Space weather; Wave propagation; Wave-particle interaction; Model Eligibility: Open to U.S. citizens Only

SF.40.01.B7620: Electromagnetic (EM) Wave Radiative Transfer through Cloudy Atmospheres and Detection of Forward/Multiply-Scatterd Light

Roadcap, John - 505-853-3711

The Associate will have the opportunity to perform fundamental investigations of EM wave radiative transfer through hazy, cloudy, and precipitating atmospheres and detection of transmitted and reflected multiply-scattered light sources through these media. Phenomena include incident EM wave scattering, absorption, and emission by polydisperse particles with non-uniform shapes and complex permittivities, phase function, and polarized wave intensity as functions of scattering angle, molecular spectroscopic absorption, and molecular scattering. Wavelengths of interest span the ultraviolet through infrared and microwave spectral regions and can involve monochromatic or broadband sources. The development of novel time series analysis methods using advanced digital signal processing and remote-sensing techniques to detect transmitted and reflected multiply-scattered point source intensities will also be considered. The Associate will be expected to document, interpret, and explain their findings associated with these phenomena.
References
Balanis CA: Advanced Engineering Electromagnetics. New York: John Wiley & Sons, 1018: 2012
Roadcap JR, et al: Journal of Applied Remote Sensing 9(1), 096049 (2015), doi.org/10.1117/IJRS 9.096049.
Keywords:
Electromagnetic wave; Radiative transfer; Scattering; Absorption; Emission; Polarization; Refraction; Fourier transform; Digital signal processing; Remote sensing;
Eligibility: Open to U.S. citizens Only
Level: Open to Regular and Senior applicants

SF.40.01.B7488: Satellite Guidance, Navigation, and Control Applied to Close-Proximity Missions

Lovell, T.A - (505) 853-4132

The Air Force has a pressing need to better understand and utilize the dynamics of relative satellite motion (i.e., the motion of one satellite with respect to one or more other satellites) for close-proximity missions. These missions include both cluster/formation missions and rendezvous/proximity operations missions. The former missions typically involve multiple satellites with maneuvering capability and communication links (both with the ground and one another) performing some cooperative task (e.g., remote sensing), whereas the latter missions typically involve a lesser degree of maneuverability, connectivity, and cooperation among the satellites. Areas of relevant research include:

(1) Modeling of Relative Orbit Dynamics. The relative motion between two or more satellites in close proximity can be modeled in unique ways. The governing equations for such motion can account for a variety of physical phenomena and maybe either linear or nonlinear, time-varying, or time-invariant. We are particularly interested in the formulation of relative dynamics in such a way that it can be characterized geometrically (as opposed to using Cartesian coordinates), as well as in ways that lend themselves to the applications below. A separate area involves the analysis of natural revisit opportunities for proximity operations between satellites, using concepts such as synodic period.

(2) Relative Navigation for Satellite Systems. Satellites flying in close proximity have tight navigation requirements that may exceed the state-of-the-art in relative and autonomous navigation. These requirements include accurate estimation of both the position/velocity and attitude of the satellites. Sensing schemes include differential GPS and intersatellite ranging, using vision sensors such as radar and LIDAR. In addition to sensing, the navigation task requires accurate estimation techniques. We are particularly interested in improved filter design that may involve maximum on-board autonomy (i.e., minimum interaction from the ground), faster computation methods, use of new or unique propagation models, the ability to handle a wide variety of observation types from multiple satellites, and/or applicability over a wide range of orbital regimes.

(3) Guidance/Control Algorithms for Relative Satellite Motion. Satellites flying in close proximity have unique control requirements. Guidance algorithms must be designed taking into account both mission requirements/constraints and the natural orbital dynamics of the system. In addition, control of the satellites must often be accomplished in an optimal fashion, where trajectory time and/or fuel expenditure are of concern. The versatility of satellite cluster missions allows for reconfiguration of the satellites to perform different missions or to account for the addition or deletion of members to the cluster. Such reconfiguration will require sophisticated guidance and control algorithms. Ware particularly interested in the development of open- and/or closed-loop control algorithms for relative satellite trajectories and optimization of these trajectories. The former area may involve both centralized and decentralized control, as well as hierarchical control; while the latter area may involve both conventional (e.g., LQR, gradient-based) and modern (e.g., genetic algorithm) optimization schemes. In addition to the close-proximity maneuvering described above, we would also like to study orbit transfer techniques to achieve rendezvous, whether based on conventional methods (e.g., Lambert transfer) or lesser known methods (e.g., hodograph theory).

Keywords:

Orbital mechanics; Astrodynamics; Satellite; Guidance; Navigation; Control

Citizenship: Open to U.S. citizens and permanent residents

Level: Open to Regular and Senior applicants

SF.40.01.B7343: Space Structures

Footdale, J.N. - 505-853-5358

Getting to and operating in space presents unique structural challenges. Structural mass efficiency, thermal response, precision, dimensional stability, packaging, and deployment all play critical roles in determining the performance of spacecraft sensor systems and addressing these needs leads to methods and architectures that are dramatically different from terrestrial systems. Work focuses on research related to structural aspects of spacecraft systems and should be traceable to improvements in systems of interest to the Department of Defense. Traditional applications include radio frequency reflectors, optical mirrors, phased array antennas, solar arrays, solar sails, and instrument booms. Structural aspects of new and emerging architecture are also highly encouraged. *Keywords: Space structure; Deployable structure; Space antenna; Mirror; solar array; Solar sail; Dimensional stability; Space sensor; Reflector; *Eligibility: Citizenship: Open to U.S. citizens only. Level: Open to Regular and Senior applicants

SF.40.01.B6879: Advanced Structures and Materials for Space Power Generation

Hausgen, Paul - (505) 846-9219

The types of space missions that the Air Force conducts is expanding to include both traditional spacecraft (e.x. AEHF, GPS, etc.) as well as smaller and more agile spacecraft, as described in the Space Warfighting Construct (SWC). On-orbit performance of power generation systems is critical to mission success for all of these missions. Traditional spacecraft continue to be enhanced by use of higher performance (improved efficiency, lower mass, lower cost) and more radiation tolerant solar cell technologies. Given the intention to rapidly field SWC spacecraft, they are likely to be enhanced by developing much lower cost solar cells and arrays that still have acceptable performance. In addition, the SWC spacecraft may have shorter operational lifetimes, thus potentially reducing the requirement for high radiation tolerance. The current state-of-the-art photovoltaic cells used for space applications are multijunction devices based on the III-V material systems (e.g., GaAs, GaInP). Developments continue to push the performance of these devices to ever higher levels, with the newest devices being greater than 30% efficient and incorporating more than three subcells. To address the high cost of these devices, alternate semiconductor growth processes (high rate organo metallic vapor phase epitaxy, hydride vapor phase epitaxy) are under development. Complimenting this activity is research into technologies to reduce the substrate cost, either through the use of low-cost alternatives or substrate reuse technologies. Even as the III-V cells continue to advance, there are new materials and material combinations that may prove useful for space applications. For example, Perovskite cells have shown encouraging efficiency and the potential to perform in the space radiation environment. A range of novel combinations (Perovskite/Silicon, Perovskite/CdTe, etc.) are under investigation for terrestrial applications and may be suitable for space power applications that are particularly sensitive to mass and cost. For all of these advanced technologies, it is critical to be able to accurately predict their on-orbit performance. Accurate performance estimates of advanced solar cells can be very challenging because of poorly understood synergistic dependence on various space environmental factors (energetic protons/electrons, thermal, photons, and atomic oxygen). Our goal is to expand the understanding and advance solar technology through innovative research endeavors.
Exploration of next generation energy storage materials that can enable improved safety, cycling stability, and specific energy >400 Wh/kg are also of interest. Low earth orbit (LEO) cycling protocols require about 6000 cycles/year, at 30-40% DOD, for a nominal 10 year mission life, while geosynchronous earth orbit satellites require up to 2700 cycles, at 60-80% DOD over a nominal 15 year mission life. Maintaining cycle stability while increasing specific energy is an objective for energy storage in space vehicles. Potential technologies include batteries, ultracapacitors, and non-traditional, game changing energy storage technologies. Modeling efforts to understand the fundamental properties of novel materials and charge/discharge behavior as it relates to cell performance are also of interest. The goal of these efforts is to expand the understanding of novel energy storage materials and technologies suitable for space vehicles through innovative experimental and computational research projects.

SF.40.01.B6640: Theoretical Studies of Optical Excitation, Quantum Transport, and Ultrafast Carrier-Scattering Dynamics

Huang, D - (505) 846-5788

Research involves theoretical studies and numerical calculations of optical excitation, quantum transport, strong interaction of light with matters, and ultrafast dynamics of carrier scattering in low-dimensional semiconductor systems such as quantum well, quantum wire, and quantum dots. For optical excitations, the research will focus on many-body effects on absorption, photoluminescence and inelastic-scattering spectra. For quantum transports, the research will center on effects of elastic scattering, inelastic phonon scattering, and electron-electron scattering on conductances and thermo-electric powers of electrons. For strong interaction of light with matters, the research will emphasize the effects of electronic quantum interference and photonic-crystal cavity on nonlinear optics. For ultrafast dynamics of carrier scattering, the research will focus on quantum kinetics, time-resolved optical spectra, and laser damage. Eligibility: Open to U.S. citizens Only References: Huang DH, et al: Physical Review B71: 195205, 2005; Huang DH, et al: Physical Review B71: 045204, 2005

SF.40.01.B5453: Electronic Transport in Crystalline and Amorphous Chalcogenide

Edwards, A.H - (505) 853-6042

We have long recognized that chalcogenide materials such as GeTe, Sb2Te3, and As2Te3 undergo very rapid crystalline-amorphous phase transitions when subjected to either laser light or to electrical current. These materials have recently been incorporated into practical commercial products such as the re-writable DVD. There is no cogent explanation for the time scale of this transition (~tens of nanoseconds). We are also interested in the interaction of these materials with materials used in silicon technology. Our research has combined both experimental and theoretical approaches. Opportunities are available to perform experimental studies of electronic transport in these materials. The applicant will be expected to conduct a wide variety of experiments, including measurements of the Seebeck and Hall coefficients, and of thermal diffusivity; design and set up experiments; and collaborate with other, in-house groups working on modeling and theory of the phase transition. Eligibility: Open to U.S. citizens Only

SF.40.01.B5409: Multiscale Modeling Applied to Chalcogenide Alloys in Reconfigurable Electronics

Edwards, A.H - (505) 853-6042

We have long recognized that chalcogenide materials such as GeTe, Sb2Te3, and As2Te3 undergo very rapid crystalline-amorphous phase transitions when subjected to either laser light or to electrical current. These materials have recently been incorporated into practical commercial products such as the re-writable DVD. There is no cogent explanation for the time scale of this transition (~tens of nanoseconds). We are also interested in the interaction of these materials with materials used in silicon technology. Our research has combined both experimental and theoretical approaches to study them. Opportunities are available to work on the simulation of the phase transitions (both directions), and on inter-diffusion and the concomitant changes in material properties using a hierarchy of techniques that includes density functional theory, classical molecular dynamics, tight-binding molecular dynamics, classical Monte Carlo, and classical continuum methods. There are also opportunities to influence the direction of our work and develop new hybrid algorithms that would couple two or more techniques. Applicants will be able to interact with a strong in-house experimental effort that includes XAFS, SIMS, SEM, TEM, Hall, Seebeck, and thermal diffusivity measurements. Local computational resources include a 46-node Beowulf cluster and access to shared DOD resources. Eligibility: Open to U.S. citizens Only

SF.40.01.B5113: Advanced Spacecraft Guidance, Navigation, & Control

Erwin, R.S - (505) 846-9816

This project seeks to develop new methods, techniques, and algorithms for challenging spacecraft guidance, navigation, and control (GNC) problems. Specifically, new approaches are being developed for (a) autonomous spacecraft relative-motion guidance and navigation approaches for rendezvous & proximity operations missions, (b) advanced attitude estimation & control algorithms for control-moment gyro, reaction wheel, and thruster-actuated spacecraft systems, (c) analysis and development of techniques for networked autonomous spacecraft performing collaborative missions such as geolocation of terrestrial search and rescue beacons or coordinated inspection of proximity spacecraft, and (d) image-based relative navigation and pose/feature extraction algorithms enabling rendezvous and proximity operations missions. Research proposals that address one or more of these topics from a theoretical or experimental point of view are of interest. This research can make use of the experimental facilities at AFRL, including a spherical air bearing attitude control and determination testbed, image-based spacecraft navigation facilities, rendezvous & proximity operations simulation capabilities, and autonomous multi-spacecraft testbeds. Keywords: estimation; navigation; guidance; control; spacecraft; satellites; robotics; image processing; networked control; coordinated control; autonomous systems; References: Baldwin, M., Erwin, R. S., and Kolmanovsky, I. V., “Robust Controller for Constrained Relative Motion Maneuvering with Disturbance Rejection,” Proc. AIAA Guid., Nav., & Contr. Conf., AIAA 2013-4721, Boston, MA, August 2013. Hussein, I. I., Sorrentino, F., and Erwin, R. S., “Bayesian Hybrid Estimation of LTI Networked Systems using Finite Set Statistics” Proc. Amer. Contr. Conf., pp. 396 – 401, Washington, D.C., June 2013. Weiss, A., Baldwin, M., Petersen, C., Erwin, R. S., and Kolmanovsky, I. V. “Spacecraft Constrained Maneuver Planning for Moving Debris Avoidance Using Positively Invariant Constraint Admissible Sets,” Proc. Amer. Contr. Conf., pp. 4809 – 4814, Washington, D.C., June 2013. Luna, J. M., Abdallah, C. T., and Erwin, R. S., “Delay-dependent Stabilization of a Class of Nonlinear Time-delay Systems with Time-varying State and Input Delays,” Proc. Amer. Contr. Conf., pp. 3925 – 3931, Montreal, Canada, June 2012. Allgeier, S. E., Erwin, R. S., and Fitz-Coy, N. G., “Velocity Extrema in Spacecraft Formation Flight,” Proc. 22nd AAS/AIAA Space Flight Mechanics Meeting, AAS 12 – 152,pp. 763 – 781,Charleston, SC, January 2012. Eligibility: Open to U.S. citizens Only Level: Open to Regular and Senior applicants

SF.40.01.B5112: Control- and Game-Theoretic Approaches for Resilient Satellite Radio Communications

Pham, Khanh - 505-846-4823

Satellite communications (SATCOM) with enhancements of radio interference mitigation, low probability of interception (LPI), and low probability of detection (LPD) can improve multi-user access, bit-error-rate performance, and throughput efficiency in congested and contested radio environments. Research opportunities exist to explore the use of game-theoretic approaches to physical, medium access control, and network layers of satellite user terminals and ground hub system controllers that are desired to have radio interference resistance, LPI, LPD, and low cost in anti-access and area-denial radio environments. Specifically, related endeavors using game-theoretical frameworks include the development of ground hub system controllers and user terminals corresponding to dynamic resource and link margin assignments, to which dynamic multi-agent interactions among user terminals, ground hub system controllers, and adversarial actors are optimized for burst carrier frequencies, bandwidths, durations, and repetition intervals. With regard to control-theoretic approaches, additional emphases may also be placed on open-loop forward link time synchronization, closed-loop return link time synchronization to align both time and phase scales of ground hubs, satellite transponders and user terminals in presence of filter delays, phase delays and phase noises, frequency drifts by local oscillators, and amplitude modulation and phase modulation effects.
REFERENCES:
1. Q. Wang, T. Nguyen, K. Pham, and H. Kwon, “Mitigating Jamming Attack: A Game-Theoretic Perspective,” IEEE Military Communications, 2017
2. D. Shen, Z. Shu, X. Tian, G. Chen, and K. Pham, “A Game-Theoretic DRA Approach for Improved Spread Spectrum Frequency Hopped Waveforms Performance in the Presence of Smart Jammers,” IEEE Cognitive Communications for Aerospace Applications Workshop, Cleveland, OH, 2017
3. M. Hannon, S. Feng, H. M. Kwon, and K. D. Pham, “Jamming Statistics-Dependent Frequency Hopping,” IEEE Military Communications Conference, Baltimore, MD, 2016
4. Tian X, Tian Z, Pham K, Blasch E, Shen D: Jamming/Anti-jamming Game with a Cognitive Jammer in Space Communication. Proceedings of SPIE 8385, Sensors and Systems for Space Applications V, 2012
KEYWORDS: Satellite communications; User terminals; Ground hub system controllers; Low probability of interception; Low probability of detection; Radio interference mitigation; Dynamic resource allocation; Link margin assignment; Multi-agent interactions; Online learning; Open-loop forward link time synchronization; Closed-loop return link time synchronization; Filter delays; Phase delays; Phase noises; Frequency drifts; Local oscillators

SF.40.01.B5111: Data Fusion, Reasoning, Decision-Making, and Verification/Validation Approaches for Autonomous Spacecraft

Erwin, R.S - (505) 846-9816

The ability of spacecraft to implement high-level reasoning and decision-making approaches is key to achieving several Air Force capability goals for future space systems. Benefits of on-board autonomy for spacecraft include reduced manpower requirements for mission operations, allows greater span of control for human operators and decision makers, and enables spacecraft to accomplish missions and respond to changing conditions that are un-achievable under ground-control due to communication link un-availability or latency. There are a number of technical hurdles that must be overcome before on-board algorithms will be allowed to control flight- and safety-critical functions on operational spacecraft, including analytic guarantees for the embedded control and reasoning systems used in flight software, and the ability to use systematic and rigorous verification and validation techniques that reduce the probability of undesired system behavior due to emergent behavior or implementation errors beyond what can be achieved using brute-force simulation approaches (e.g., Monte-Carlo testing). This topic seeks to develop new approaches for provably correct reasoning and decision-making algorithms (suitable for direct software implementation), the development and application of rigorous approaches for error detection and/or constraint-violating behavior of non-proven algorithms and software, as well as the application of these methodologies to spacecraft autonomy applications of interest. The project will involve cross-disciplinary research in mathematics, systems and control theory, computer science, and software engineering. Keywords: space; autonomy; decision; estimation; data fusion; reasoning; verification; validation; uncertainty; correctness; References: 1. Chien, S., et. al. “Using Autonomy Flight Software to Improve Science Return on Earth Observing One,” AIAA J. Aerospace Computing, Information, and Communication, Vol. 2, pp. 196 – 216, 2005. 2. Brat, G., et. al. “Experimental Evaluation of Verification and Validation Tools on Martian Rover Software,” Formal Methods in System Design, Vol. 25, pp. 167–198, 2004. 3. Wongpiromsarn, T., Topcu, U., and Murray, R. M., “Automatic Synthesis of Robust Embedded Control Software,” AAAI Spring Symposium on Embedded Reasoning (22-24 Mar 2010, Stanford), http://www.cds.caltech.edu/~murray/preprints/wtm10-aaai.pdf (11 August 2010). Eligibility: Open to U.S. citizens Only

SF.30.04.B7769: Millimeter-Wave Radio Frequency Propagation Modeling and Validation

Lane, Steven - (505) 846 9944

The 71-76 GHz and 81-86 GHz bands have the potential to provide ultrahigh bandwidth (gigabit per second [Gbps] data rates) point-to-point communications between a satellite and a ground station. However, one of the most crucial problems in achieving this communication link is the uncertainty of signal attenuation, phase distortion, and depolarization resulting from atmospheric absorption, scintillation, and meteorological effects (e.g., rain fade). High fidelity propagation models must be developed, statistically validated, and correlated to meteorological parameters and climatic regions as was done for the Ka-band in the 1990s to enable the Air Force to accomplish feasibility studies, systems engineering, and availability modeling to support future military satellite system architectures. The objective of this research is to develop improved models to predict path attenuation, phase distortion, and depolarization, particularly at 71-76 GHz and 81-86 GHz. Key parameters affecting channel propagation must be identified and the functional relationship modeled. Some of the goals of this research are (1) a model development of key communication channel properties (attenuation, phase distortion, depolarization); (2) identification of key parameters affecting channel properties (absorption, scattering, scintillation, humidity, moisture, hydrometers, rain-rate); and (3) simulations, comparison to current models We seek applicants with backgrounds in communications theory, EM theory, or physics with understanding of radio wave propagation phenomena. References: Lucente M, et al: Proceedings of the IEEE: 2011 Cianca E, et al: Proceedings of the IEEE (99)11: 2011 Keywords: Millimeter-wave; Propagation; Physics-based modeling; Communication channel properties; Atmospheric absorption; Depolarization; Scattering; Scintillation; E-band; Eligibility: Open to U.S. citizens Only Level: Open to Regular and Senior applicants

AFRL-Space Vehicles

Dr. SAAVEDRA, JUDITH
Learning Officer
AFRL/RV
AFRL/RV, Maryland 20850
Telephone: 505-853-9987
Email: judith.saavedra@us.af.mil