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H TA05 Communication and Navigation INTRODUCTION The draft roadmap for technology area (TA) 05, Communication and Navigation, consists of six level 2 tech - nology subareas:1 • 5.1 Optical Communication and Navigation • 5.2 Radio Frequency Communication • 5.3 Internetworking • 5.4 Position, Navigation, and Timing • 5.5 Integrated Technologies • 5.6 Revolutionary Concepts The Communication and Navigation TA supports all NASA space missions with the development of new capabilities and services that make NASA missions possible. Communication links are the lifelines to spacecraft, providing commanding, telemetry, and science data transfers as well as navigation support. Planned missions will require a slight improvement in communication data rate, as well as moderate improvements in navigation precision. However, advancement in communication and navigation technology will allow future missions to implement new and more capable science instruments, greatly enhance human missions beyond Earth orbit, and enable entirely new mission concepts. This will lead to more productivity in science and exploration missions, as well as provide high-bandwidth communications links that will enhance the public’s ability to be a part of NASA programs of exploration and discovery. The roadmap describes the communication and navigation technology developments that are necessary to meet the needs of future missions, provide enhanced capabilities, or enable new mission concepts. This includes identification of representative future missions and key capabilities and investments that will enable or enhance these missions. The roadmap focuses on several key issues for the future of communications: development of radio frequency (RF) technology while initiating a parallel path to develop optical communications capability, application of Earth’s internetworking technology and processes to reduce operational costs through simplified 1 The draft space technology roadmaps are available at http://www.nasa.gov/offices/oct/strategic_integration/technology_roadmap.html. 167
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168 NASA SPACE TECHNOLOGY ROADMAPS AND PRIORITIES data handling and distribution, improvements in navigation accuracy, development of integrated communication systems, and identification of potentially revolutionary technologies. Before prioritizing the level 3 technologies included in TA05, several technologies were renamed, deleted, or moved. The changes are explained below and illustrated in Table H.1. The complete, revised technology area breakdown structure (TABS) for all 14 TAs is shown in Appendix B. TABLE H.1 Technology Area Breakdown Structure for TA05, Communication and Navigation NASA Draft Roadmap (Revision 10) Steering Committee-Recommended Changes Two technologies have been merged and one has been renamed. TA05 Communication and Navigation 5.1. Optical Comm. and Navigation 5.1.1. Detector Development 5.1.2. Large Apertures 5.1.3. Lasers 5.1.4. Acquisition and Tracking 5.1.5. Atmospheric Mitigation 5.2. Radio Frequency Communications 5.2.1. Spectrum Efficient Technologies 5.2.2. Power Efficient Technologies 5.2.3. Propagation 5.2.4. Flight and Ground Systems 5.2.5. Earth Launch & Reentry Comm. 5.2.6. Antennas 5.3. Internetworking 5.3.1. Disruptive Tolerant Networking 5.3.2. Adaptive Network Topology 5.3.3. Information Assurance 5.3.4. Integrated Network Management 5.4. Position, Navigation, and Timing 5.4.1. Timekeeping Merge 5.4.1 and 5.4.2: 5.4.2. Time Distribution Rename: 5.4.1. Timekeeping and Time Distribution 5.4.3. Onboard Autonomous Navigation and Maneuver Delete: 5.4.2. Time Distribution 5.4.4. Sensors and Vision Processing Systems 5.4.5. Relative and Proximity Navigation 5.4.6. Auto Precision Formation Flying 5.4.7. Auto Approach and Landing 5.5. Integrated Technologies 5.5.1. Radio Systems 5.5.2. Ultra Wideband 5.5.3. Cognitive Networks 5.5.4. Science from the Comm. System 5.5.5. Hybrid Optical Comm. and Nav. Sensors 5.5.6. RF/Optical Hybrid Technology 5.6. Revolutionary Concepts 5.6.1. X-Ray Navigation 5.6.2. X-Ray Communications 5.6.3. Neutrino-Based Navigation and Tracking 5.6.4. Quantum Key Distribution 5.6.5. Quantum Communications 5.6.6. SQIF Microwave Amplifier 5.6.7. Reconfigurable Large Apertures Rename: 5.6.7. Reconfigurable Large Apertures Using Nanosat Constellations NOTE: Technologies 5.4.1, Timekeeping, and 5.4.2, Time Distribution, have been merged and renamed: 5.4.1 Timekeeping and Time Distribu- tion because the technologies are very similar and it would be most effective to develop them together. Technology 5.6.7, Reconfigurable Large Apertures, has been renamed 5.6.7 Reconfigurable Large Apertures Using Nanosat Constellations to better indicate the content of this technol- ogy as described in the TA05 roadmap.
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169 APPENDIX H TOP TECHNICAL CHALLENGES The panel identified three top technical challenges for TA05. They are listed below in priority order. 1. Autonomous and Accurate Navigation: Meet the navigation needs of projected NASA missions by developing means for more autonomous and accurate absolute and relative navigation. NASA’s future missions show a diverse set of navigational challenges that cannot be supported with cur- rent methods. Precision position knowledge, trajectory determination, cooperative flight, trajectory traverse, and rendezvous with small bodies are just some of the challenges that populate these concepts. In addition, NASA spacecraft will need to do these things farther from Earth and more autonomously. Proper technology investment can solve these challenges and even suggest new mission concepts. 2. Communications Constraint Mitigation: Minimize communication data rate and range constraints that impact planning and execution of future NASA space missions. A recent analysis of NASA’s likely future mission set indicates that communications performance will need to grow by about a factor of ten every ~15 years just to keep up with projected robotic mission requirements. A second dimension of the challenge is measured simply in bits per second. History has shown that NASA mis - sions tend to return more data with time according to an exponential “Moore’s law.” Missions will continue to be constrained by the legally allocated international spectral bandwidth. NASA’s S-band is already overcrowded and there are encroachments at other bands. Many of the complex things future missions will need to do are hampered by keeping Earth in the real-time decision loop. Often, a direct link to Earth may not even be available when such decisions are desired. This can be mitigated by making decisions closer to the platform—minimizing reliance on Earth operations. Advancements in communications and navigation infrastructure will allow information to be gathered locally and computation to be performed either in the spacecraft or shared with nearby nodes. Clearly this goal is coupled with the need for increased autonomy and flight computing. 3. Information Delivery: Provide integrity and assurance of information delivery across the solar system. Future missions will include international partnerships and increased public interaction. This will imply increased vulnerability to information compromise. As mentioned in the 2012 Science and Technology Priori - ties Memo from the White House, NASA needs to “Support cybersecurity R&D to investigate novel means for designing and developing trustworthy cyberspace—a system of defensible subsystems that operate safely in an environment that is presumed to be compromised.” As internetworking extends throughout the solar system, the communications architecture needs to operate in a safe and secure manner. QFD MATRIX AND NUMERICAL RESULTS FOR TA05 The process used to evaluate the level 3 technologies is described in detail in Chapter 2. The results of the evaluation are shown in Figures H.1 and H.2, which show the relative ranking of each technology. The panel assessed four of the technologies as high priority. Three of these were selected based on their QFD scores, which significantly exceeded the scores of lower ranked technologies. After careful consideration, the panel also desig - nated 5.5.1 Radio Systems as a high-priority technology.2 2 In recognition that the QFD process could not accurately quantify all of the attributes of a given technology, after the QFD scores were compiled, the panels in some cases designated some technologies as high priority even if their scores were not comparable to the scores of other high-priority technologies. The justification for the high-priority designation of all the high-priority technologies for TA05 appears in the section titled “High Priority Level 3 Technologies,” below.
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170 NASA SPACE TECHNOLOGY ROADMAPS AND PRIORITIES ls oa ds lG ee na N ch io s at es Te N en o ce er bl pa ds A na SA os ee so er g N A ea in d) -N -A SA R m te on on d A Ti gh an N N N d ei rt ith ith ith an k (W fo is y w w w rit ng Ef lR e t t t rio or en en en ci d ca an Sc en lP it nm nm nm ni ef qu ne ch e FD en lig lig lig m Se Pa Te Ti Q B A A A Multiplier 27 5 2 2 10 4 4 0/1/3/9 0/1/3/9 0/1/3/9 0/1/3/9 1/3/9 -9/-3/-1/1 -9/-3/-1/0 Alignment Risk/Difficulty Technology Name Benefit 148 M 5.1.1. Detector Development 3 9 3 1 3 -3 -1 134 M 5.1.2. Large Apertures 3 9 1 0 3 -3 -3 144 M 5.1.3. Lasers 3 9 1 1 3 -3 -1 142 M 5.1.4. Acquisition and Tracking 3 9 1 0 3 -3 -1 136 M 5.1.5. Atmospheric Mitigation 3 9 1 1 3 -3 -3 92 M 5.2.1. Spectrum Efficient Technologies 1 9 3 0 3 -3 -1 126 M 5.2.2. Power Efficient Technologies 1 9 9 3 3 1 -1 58 L 5.2.3. Propagation 1 9 1 1 3 -9 -3 94 M 5 5.2.4. Flight a d G ou d Sys e s and Ground Systems 1 9 3 1 3 -3 3 -1 56 L 5.2.5. Earth Launch and Reentry Communications 1 9 1 0 3 -9 -3 146 M 5.2.6. Antennas 3 9 3 0 3 -3 -1 168 M 5.3.1. Disruptive Tolerant Networking 3 9 3 3 3 1 -1 188 H 5.3.2. Adaptive Network Topology 3 9 3 3 9 -9 -1 52 L 5.3.3. Information Assurance 1 9 9 0 1 -9 -3 154 M 5.3.4. Integrated Network Management 3 9 3 0 3 -1 -1 200 H 5.4.1. Timekeeping and Time Distribution 3 9 9 3 9 -9 -1 206 H 5.4.3. Onboard Autonomous Navigation and Maneuvering 3 9 3 0 9 -3 -1 146 M 5.4.4. Sensors and Vision Processing Systems 3 9 3 0 3 -3 -1 146 M 5.4.5. Relative and Proximity Navigation 3 9 3 0 3 -3 -1 172 M 5.4.6. Auto Precision Formation Flying 3 3 1 0 9 -3 -1 112 M 5.4.7. Auto Approach and Landing Auto Approach and Landing 3 3 1 0 3 -3 -3 -1 -1 164 H* 5.5.1. Radio Systems 3 9 3 9 3 -3 -1 148 M 5.5.2. Ultra Wideband Communications 3 3 1 0 9 -9 -1 90 M 5.5.3. Cognitive Networks 3 3 3 3 3 -9 -3 56 L 5.5.4. Science from the Communication System 1 3 0 0 3 -3 -1 58 L 5.5.5. Hybrid Optical Communication and Navigation Sensors 1 3 1 0 3 -3 -1 70 L 5.5.6. RF/Optical Hybrid Technology 1 9 3 1 3 -9 -1 ‐23 L 5.6.1. X-Ray Navigation 0 3 0 0 1 -9 -3 ‐38 L 5.6.2. X-Ray Communications 0 0 0 0 1 -9 -3 ‐62 L 5.6.3. Neutrino-Based Navigation and Tracking 0 0 0 0 1 -9 -9 ‐21 L 5.6.4. Quantum Key Distribution 0 3 1 0 1 -9 -3 ‐45 L 5.6.5. Quantum Communications 0 3 1 0 1 -9 -9 12 L 5.6.6. SQIF Mi 66 Microwave A lifi Amplifier 1 3 3 1 1 -9 9 -3 3 5.6.7. Reconfigurable Large Apertures Using Nanosat 4 L 1 3 0 0 1 -9 -3 Constellations FIGURE H.1 Quality function deployment (QFD) summary matrix for TA05 Communication and Navigation. The justification for the high-priority designation of all high-priority technologies appears in the section “High-Priority Level 3 Technologies.” H = High Priority; H* = High Priority, QFD score override; M = Medium Priority; L = Low Priority. CHALLENGES VERSUS TECHNOLOGIES Figure H.3 shows the relationship between the individual level 3 TA10 technologies and the top technical challenges. Note that the lowest-priority technologies as determined by QFD rankings tend not to be strongly con - nected to the top technical challenges. All of the high-priority technologies have a strong connection to two of the top technical challenges. This shows a good level of consistency between the evaluations and the QFD rankings. HIGH-PRIORITY LEVEL 3 TECHNOLOGIES Panel 2 identified four high-priority technologies in TA05. The justification for ranking each of these technolo- gies as a high priority is discussed below.
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171 APPENDIX H 0 50 100 150 200 250 300 350 400 5.4.3. Onboard Autonomous Navigation and Maneuvering High Priority 5.4.1. Timekeeping and Time Distribution 5.3.2. Adaptive Network Topology 5.4.6. Auto Precision Formation Flying Medium Priority 5.3.1. Disruptive Tolerant Networking 5.5.1. Radio Systems 5.3.4. Integrated Network Management 5.1.1. Detector Development 5.5.2. Ultra Wideband Communications 5.2.6. Antennas 5.4.4. Sensors and Vision Processing Systems 5.4.5. Relative and Proximity Navigation 5.1.3. Lasers 5.1.4. Acquisition and Tracking 5.1.5. Atmospheric Mitigation 5.1.2. Large Apertures 5.2.2. Power Efficient Technologies 5.4.7. Auto Approach and Landing 5.2.4. Flight and Ground Systems 5.2.1. Spectrum Efficient Technologies 5.5.3. Cognitive Networks 5.5.6. RF/Optical Hybrid Technology Low Priority 5.2.3. Propagation 5.5.5. Hybrid Optical Communication and Navigation Sensors 5.2.5. Earth Launch and Reentry Communications 5.5.4. Science from the Communication System 5.3.3. Information Assurance 5.6.6. SQIF Microwave Amplifier 5.6.7. Reconfigurable Large Apertures Using Nanosat Constellations 5.6.4. Quantum Key Distribution 5.6.1. X‐Ray Navigation 5.6.2. X‐Ray Communications High Priority (QFD Score Override) 5.6.5. Quantum Communications 5.6.3. Neutrino‐Based Navigation and Tracking FIGURE H.2 Quality function deployment rankings for TA05 Communication and Navigation. Technology 5.4.3, Onboard Autonomous Navigation and Maneuvering Systems Onboard autonomous navigation and maneuvering (OANM) techniques are critical for improving the capabili- ties and reducing the support requirements for many future space missions. By accurately determining the position and attitude of the vehicle, the dependence on routine position fixes from Earth will be greatly reduced, freeing the communication network for other tasks. The onboard maneuver planning and execution monitoring will increase the vehicle agility, enabling new mission capabilities currently not possible given the round-trip time delay to Earth and the loss of communication during atmospheric reentry. It could also reduce costs by helping to eliminate the large work force required to support the routine operations of the spacecraft. Given the previous flight demonstrations, e.g., DS-1 and EO-1, some basic aspects of the OAMN are at TRL 9, but the new advanced capabilities required for future missions are closer to a TRL of 3. The research and flight demonstrations needed for this technology to be accepted for future missions are well aligned with the NASA experience and capabilities and consistent with NASA’s past roles. It is possible that NASA will be able to draw upon new algorithms and capabilities resulting from the significant current interest in autonomous robotics and UAVs, but the mission and autonomy requirements in these domains differ significantly from NASA’s needs. There is more overlap with Department of Defense work on autonomous underwater robotics, given the truly remote operations with limited off-board communication capabilities that often exist. However, given the length, variety, and complexity of the missions, the challenges faced by NASA are unique and it is very unlikely that they will be fully addressed by an external research organization. As such, NASA investment in this technology area is critically important. The panel determined that the OANM systems provide a major benefit due to the technology’s potential to sig - nificantly improve the capabilities/performance and reduce the operational cost of future missions. The alignment
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172 NASA SPACE TECHNOLOGY ROADMAPS AND PRIORITIES Top Technology Challenges 1. Autonomous and Accurate Navigation: Meet the 2. Communications Constraint 3. Information Delivery: Mitigation: Minimize navigation needs of projected Provide integrity and communication data rate and NASA missions by developing assurance of information range constraints that impact means for more autonomous delivery across the solar planning and execution of and accurate absolute and system. future NASA space missions. relative navigation. Priority TA 05 Technologies, Listed by Priority ● ● 5.4.3. Onboard Autonomous Navigation and Maneuvering H ● ● 5.4.1. Timekeeping and Time Distribution H ○ ● ● 5.3.2. Adaptive Network Topology H ○ ● ● 5.5.1. Radio Systems H ○ 5.4.6. Auto Precision Formation Flying M ○ ○ 5.3.1. Disruptive Tolerant Networking M ○ ○ 5.3.4. Integrated Network Management M ○ 5.1.1. Detector Development M ○ 5.5.2. Ultra Wideband Communications M ○ 5.2.6. Antennas M ○ 5.4.4. Sensors and Vision Processing Systems M ○ 5.4.5. Relative and Proximity Navigation M ○ ○ 5.1.3. Lasers M ○ ○ 5.1.4. Acquisition and Tracking M ○ ○ 5.1.5. Atmospheric Mitigation M ○ 5.1.2. Large Apertures M ○ ○ 5.2.2. Power Efficient Technologies M ○ 5.4.7. Auto Approach and Landing M ○ ○ 5.2.4. Flight and Ground Systems M ○ ○ 5.2.1. Spectrum Efficient Technologies M ○ ○ 5.5.3. Cognitive Networks M ○ ○ 5.5.6. RF/Optical Hybrid Technology L ○ 5.2.3. Propagation L ○ ○ 5.5.5. Hybrid Optical Comm. and Nav. Sensors L ○ 5.2.5. Earth Launch and Reentry Commmunications L 5.5.4. Science from the Comm. System L ○ 5.3.3. Information Assurance L 5.6.6. SQIF Microwave Amplifier L 5.6.7. Reconfigurable Large Apertures using Nanosat Constellations L 5.6.4. Quantum Key Distribution L ○ 5.6.1. X-Ray Navigation L 5.6.2. X-Ray Communications L 5.6.5. Quantum Communications L 5.6.3. Neutrino-Based Navigation and Tracking L Strong Linkage: Investments by NASA in this technology would likely have a major impact in addressing ● this challenge. Moderate Linkage: Investments by NASA in this technology would likely have a moderate impact in ○ addressing this challenge. Weak/No Linkage: Investments by NASA in this technology would likely have little or no impact in [blank] addressing the challenge. FIGURE H.3 Level of support that the technologies provide to the top technical challenges for TA05 Communication and Navigation. to NASA’s needs is high because it will impact deep space exploration with crew, robotic science missions, planetary landers and rovers. The alignment with other aerospace needs is considered to be medium, as some of the automation and planning algorithms will overlap with the DOD/commercial space missions and other robotic applications, but the alignment with national needs is considered to be low as this work will really only be relevant to spacecraft. The risk is assessed to be moderate to high, within the bounds of NASA’s acceptable risk levels for technology development. Of particular importance is the observation that the autonomous navigation and maneuver planning algorithms can be added (and verified) incrementally on near-term missions to enable a solid foundation
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173 APPENDIX H to be established for future missions. This approach could be used to appropriately scale the workforce required to address the OANM technology challenges at a moderate level of effort. Due to the potential for major mission improvements and cost savings, strong alignment with NASA needs, and reasonable risk and development effort, OANM are rated as high-priority technologies. Technology 5.4.1, Timekeeping and Time Distribution NASA provides communications and navigation infrastructure for its missions. Underlying this infrastructure are atomic clocks and time transfer hardware and software. New, more precise atomic clocks operating in space, as well as new and more accurate means of time distribution and synchronization of time among such atomic clocks (e.g., optical transmitters and receivers operating in the space environment), will enable the infrastructure improvements and expansion NASA requires in the coming decades. The TRL of timekeeping and distribution systems varies over a wide range from 9 for current systems all the way down to 1 for yet-to-be-proposed atomic clocks. Ground-based work3 at the National Institute of Standards and Technology (NIST) and other laboratories can be considered TRL 3-4. The planned ISS experiment ACES 4 is a scientific instrument, not routine PNT gear; TRL 3 is probably a good estimate for the status of ACES when considered for use in an operational scenario. Precision timekeeping and transfer is of interest not only to NASA but also to the defense and communica - tion industries as well as the scientific community. NASA has expertise in timekeeping and distribution in space systems via the Deep Space Network and the TDRSS. NASA collaborations with DOD, NIST, university labs, and international partners such as France and Japan will be fruitful. (Japan, France, NIST, and JPL are partners in ACES mentioned above.) NASA, with appropriate partners, could focus on miniaturizing laboratory prototypes, providing the necessary stable mechanical and thermal environment, and increasing the longevity and reliability of precision clocks and time transfer equipment. The ISS may play a role in development of timekeeping and distribution technology by providing a microgravity environment in which the technologies can be demonstrated. However, for missions beyond LEO, hardware demonstration at high radiation levels and algorithms appropriate to solar system navigation are needed. Advances in timekeeping and distribution of several orders of magnitude were judged to provide major benefits, since increased precision of timekeeping and transfer leads to increased precision of relative and absolute position and velocity which in turn provides better starting solutions to enable autonomous rendezvous, docking, landing, and formation flying remote from Earth. In addition, precision timekeeping enables new tests of fundamental physics, time and frequency metrology, geodesy, gravimetry, and ultra-high-resolution VLBI science applications. Alignment with NASA’s needs is considered high due to the substantial impact of the technologies to multiple missions in multiple mission areas including human and robotic spaceflight involving rendezvous, relative station keeping and landing missions. Similarly there is high alignment with other aerospace and non-aerospace national needs, as the benefit of precise timekeeping and synchronization of navigational and communications equipment grows with the explosive increase of data required by modern technology. The risk associated with development of precision timekeeping and distribution is judged to be moderate to high, a good fit for NASA’s technology development program. Due to their major benefits, alignment with NASA and other national needs, and reasonable risk and development effort, precision timekeeping and time distribution are rated as high-priority technologies. Technology 5.3.2, Adaptive Network Topology Adaptive Network Topology (ANT) is the capability for a network to change its topology in response to either changes or delays in the network, or additional knowledge about the relationship between the communica - tion paths. This technology area includes technologies to improve mission communication such as ad hoc and mesh networking, methods of channel access, and techniques to maintain the quality of signal across dynamic 3 See http://www.nist.gov/pml/div688/logicclock_020410.cfm. 4 See http://www.spaceflight.esa.int/users/downloads/factsheets/fs031_10_aces.pdf.
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174 NASA SPACE TECHNOLOGY ROADMAPS AND PRIORITIES networks to assure successful exchange of information needed to accommodate increased mission complexity and achieve greater mission robustness. The goal is to improve end-to-end rather than hop-to-hop performance. This was originally pursued for commercial uses. However, optimization in terrestrial networks with this method has been mostly abandoned, replaced by adding additional tall towers and other hubs. The fall in terrestrial equipment prices has obviated the need for optimization inside of a limited network. The TRL for these technologies are within the 2-5 range. They have been demonstrated in the laboratory, but no commercial or space implementation has been realized. While of strong academic interest, it is unlikely that any practical development will be done by commercial entities. However, government entities with extreme applications, such as underwater communications, are likely to pursue these capabilities. Investments within DOD are happening, but the constraints may be sufficiently different to be incompatible with NASA interests. While the basic research might be purchasable from academic or research interests sponsored by the National Science Foundation and others, applicable technology will not. Because of the lack of commercial need, NASA participation is necessary if this technology is to be developed to a level that can support NASA missions in the next decades. Access to the ISS is not a requirement for development in this technology area. The applicability of this tech - nology potentially crosscuts all missions where the end-points do not have direct line of sight communications. The distinction between disruptive tolerant networking (DTN) and ANT is debatable. The panel views DTN as a subset of ANT and this view is, in part, responsible for the high priority of ANT. The panel rated the alignment with NASA needs very high for this technology. The benefit to NASA is derived because future multi-element missions will require advanced network topologies which will need to be adaptive in order to remain robust for their applications. A high rating in the category of technical risk and reasonableness was given since this is a significant extension of prior capability, with associated risk. However, the level of risk has been mitigated by a variety of prior, small scale research projects by a number of government agencies such as DOD, the National Science Foundation, and even the National Institute for Occupational Safety and Health in the mining industry (especially following accidents). A low score for sequencing and timing stems mainly from the fact that a mission need schedule is not well defined for this technology. Technology 5.5.1, Radio Systems Radio systems technology focuses on exploiting technology advances in RF communications, PNT, and space internetworking to develop advanced, integrated space and ground systems that increase performance and efficiency while reducing cost. For example, a multipurpose software defined radio might be developed that can change its function with mission phase and requirements. While this technology can benefit from individual advancements in many of the other level 3 technologies in TA05 (antennas, atmospheric mitigation, large apertures, power efficient technologies, spectrum efficient technologies, propagation, Earth launch and reentry communication systems, and information assurance), this entry focuses on the challenges associated with integration of these advancements into operational systems. Advancements in radio systems integration focus on one of the highest priority technical challenges within TA05: Minimize communications constraints on data rate and range that impact planning and execution of future NASA space missions. Like all technologies in TA05, these advancements benefit multiple types of missions in deep space as well as near-Earth orbit. Software defined radios (SDRs) are a prime example of the challenges of integration for radio systems. These offer frequency agility and wide frequency coverage, but require broadband circuitry, broadband antennas, and sophisticated software to drive the system. While the component technologies in each of these areas are mature, integration into flight-worthy systems is still required before widespread adoption of SDRs becomes possible. SDRs can be configured for many applications such as radar, arrays for beamforming, direction finding, signal identification, etc. The radio astronomy community has substantial overlap with the technologies for future SDR implementations for receiving telescopes. The Allen Telescope Array (ATA) of the SETI Institute and the University of California at Berkeley is a prototype of what may become the standard in radio astronomy. In this case, Allen provided development funding to the SETI Institute through proof of principle and initial operations, but a lack of ongoing
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175 APPENDIX H operational funding caused the array to be mothballed. The technologies implemented in the ATA can be applied to future transmitting telescopes as well, and would be a tremendous enhancement of the capabilities of the Deep Space Network. While NASA can leverage techniques and technologies from the ATA, transmitting is atypical for the radio astronomy community and will require technology investments from NASA and others. Active antenna elements are needed for smart transmitting arrays, which could also be used for a smart receiv - ing array. It would also be useful in future relay networks and orbiting communication networks, which would enable ground users to form beams in several different directions simultaneously. This provides the following substantial simultaneous benefits: Covering large fractions of the sky on a wide range of frequencies (wavelengths of meters to millimeters); tracking or searching for multiple targets simultaneously; and nulling-out discrete or extended sources of interference while receiving faint signals from sources with only small separations in look angle and measuring their spectra, Doppler shifts, and angular structure. With this technology, NASA could improve the data rates and efficiency of communication with deep space missions, including enabling high-rate communica - tion with multiple missions simultaneously. It would also reduce the need for detailed scheduling of access to the antennas and receivers, as they can be operated simultaneously. Receiving arrays have a current TRL of ~6, but transmitting arrays are closer to the TRL 2-3 range. There may be component technologies in radar systems that can be applied to transmitting arrays, but these will need to be demonstrated in an integrated fashion to achieve a higher TRL. The DOD has highly versatile, broadly applicable radar systems that can perform many of these same functions, but to our knowledge the applicability of these systems to NASA-unique needs has not been addressed. The ISS could be used as a platform for space-based testing of new SDR integrated systems, but it is not an ideal platform due to the noisy RF environment and the number of arrays, radiators, and modules that inhibit directional line-of-sight communications. Much of the development and systems integration can be performed on the ground, especially for future Deep Space Network systems. But for space-based applications such as relay networks or formations of small satellites, the technology would get as much, if not more, benefit from initial testing on any orbiting vehicle. NASA has the expertise to take a leading role in the development of radio systems, software defined radios, and array telescopes. While some advancements could come from DOD and the National Reconnaissance Office efforts, NASA has unique requirements for low signal levels and demanding angular resolution that will not be reflected in outside agency work. Given that the commercial cell phone industry is interested in applications for future generations of cognitive radios as well, NASA could pursue joint development projects, or at minimum remain cognizant of advances made within these industries and organizations. The steering committee assessed the benefit of radio systems technologies to result in major mission perfor- mance improvements due to the potential to improve throughput, versatility, and reliability with lower impact on the host spacecraft in terms of size, weight, and power (SWAP). The alignment to NASA needs is high because improvements in communication systems will impact nearly every NASA spacecraft, including near-Earth, deep space, and human exploration missions. The alignment with other aerospace needs is moderate due to its potential impact on DOD and commercial spacecraft. The alignment with other national needs is high, as it could impact any terrestrial industry that uses radios, WiFi, cable, internet, and other communications technologies. The risk is assessed to be low to moderate, as previously developed prototypes have already demonstrated key technologies at the component or subsystem level. The remaining challenge is to integrate these with NASA communications and complete space qualification of the integrated systems. The panel overrode the QFD score for this technology to designate it as a high-priority technology because the QFD scores did not capture the value of this technology in terms of the system level advances that would occur with major improvements in radio systems. MEDIUM- AND LOW-PRIORITY TECHNOLOGIES TA05 includes 30 level 3 technologies that ranked low or medium priority. In this roadmap, two technologies (5.4.6 Autonomous Precision Formation Flying and 5.5.2 Ultra Wideband) were assessed to be medium priority because of limited alignment within multiple NASA mission areas. While several potential missions (e.g., fractionated satellites or missions with multiple spacecraft, burst transmissions
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176 NASA SPACE TECHNOLOGY ROADMAPS AND PRIORITIES between nearby spacecraft) were identified, the technologies were not broadly applicable to multiple missions in multiple NASA mission areas. Seven other medium-priority technologies were judged to provide major improvements in mission perfor- mance, but were assessed to have a lower risk level than is usually appropriate for NASA OCT technology invest - ments. These technologies included 5.3.1 Disruptive Tolerant Networking, 5.3.4 Integrated Network Management, 5.2.6 Antennas, 5.4.4 Sensors and Vision Processing Systems, 5.4.5 Relative and Proximity Navigation, 5.1.3 Lasers, and 5.1.5 Atmospheric Mitigation. For most of these technologies, the development risk is low because the underlying technology is well understood, and a gradual development program focused on advances in these areas could be formulated, tested, and applied incrementally. Five additional medium-priority technologies were also judged to provide major improvements in mission per- formance with broad applicability to multiple NASA missions, but development cost and cost risk were a concern. These technologies included 5.1.1 Detector Development, 5.1.4 Acquisition and Tracking, 5.1.2 Large Apertures, 5.4.7 Auto Approach and Landing, and 5.5.3 Cognitive Networks. Despite the potential for significant benefits, these technologies were assessed to have a high probability of encountering pitfalls which could complicate the effort and cause additional development problems, possibly leading to significant cost growth and schedule delays. The remaining three medium-priority technologies and six low-priority technologies were judged to have only minor benefits to NASA missions within the next 20 to 30 years. These technologies included 5.2.2 Power Efficient Technologies, 5.2.4 Flight and Ground Systems, 5.2.1 Spectrum Efficient Technologies, 5.5.6 RF/Optical Hybrids, 5.2.3 RF Propagation, 5.2.5 Earth Launch and Reentry Communication, 5.5.5 Hybrid Optical Communication and Navigation Sensors, 5.5.4 Science from the Communication System, and 5.3.3 Information Assurance. Each of these technologies falls into at least one of two categories: (1) technologies that are fairly mature with limited room for additional improvements (e.g., 5.2.3 RF Propagation) or (2) technologies where even substantial improvements in component or subsystem technology will not easily translate into order-of-magnitude improvements in mission performance or mission risk (e.g., 5.5.3 Information Assurance). The remaining seven low-priority technologies were judged to be so immature or impractical that no benefit is projected in the 20- to 30-year timeframe of interest. These technologies were all part of the Revolutionary Concepts section of the roadmap, and include 5.6.6 SQIF Microwave Amplifiers, 5.6.7 Reconfigurable Large Apertures Using Nanosat Constellations, 5.6.4 Quantum Key Distribution, 5.6.1 X-Ray Navigation, 5.6.5 Quantum Communications, 5.6.2 X-Ray Communications, and 5.6.3 Neutrino-Based Navigation and Tracking. The panel noted technologies where investment from other organizations outside NASA would overshadow any potential NASA investments. When this is the case, NASA’s limited funds could be better spent on areas where DOD, international space agencies, or commercial industry are not making substantial financial contributions. This impacts technologies such as 5.3.1 Disruption Tolerant Networking, 5.3.4 Integrated Network Management, and 5.1.5 Atmospheric Mitigation. NASA’s key work in these areas could focus on adapting advances made by other organizations to the specific requirements of NASA missions. OTHER GENERAL COMMENTS ON THE ROADMAP All NASA missions require communication and navigation to some degree, so the priorities developed in this section are mostly independent of the mission mix. For some missions, advances in communication throughput could enable them to carry more advanced, high-data rate instruments with significant science benefit (e.g., hyper - spectral imagers). Similarly, improvements in navigation accuracy, when coupled with coordinated improvements in guidance, autonomy, sensors, and EDL technologies, will enable high precision pinpoint landing on planetary surfaces. But in most cases, the prioritization of communication and navigation technologies is not impacted by specific missions in the mission model. PUBLIC WORKSHOP SUMMARY The workshop for the TA05 Communication and Navigation technology area was conducted by the Robot - ics, Communications, and Navigation Panel on March 29, 2011, at the Keck Center of the National Academies,
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177 APPENDIX H Washington, D.C. The discussion was led by panel chair Stephen Gorevan. He started the day by giving a general overview of the roadmaps and the NRC’s task to evaluate them. He also provided some direction for what topics the invited speakers should cover in their presentations. After this introduction, the day started with an overview of the NASA roadmap by the NASA authors, followed by several sessions addressing the key areas of the road - map. For each of these sessions, experts from industry, academia, and/or government were invited to provide a 30 to 45 minute presentation/discussion of their comments on the NASA roadmap. At the end of the day, there was approximately 1 hour for open discussion by the workshop attendees, followed by a concluding discussion by the panel chair summarizing the key points observed during the day’s discussion. Roadmap Overview by NASA The presentation by the NASA roadmap development team identified challenges faced by future interplan - etary missions, and described how improved communications and navigation can mitigate these challenges. From a technology development portfolio standpoint, the key challenge is ensuring that advancements in communica - tion and navigation are out ahead of new missions, so that the technology is sufficiently advanced that it can be incorporated in future missions without adversely impacting the critical path. The existing roadmap was developed using a previous decadal survey, but a new one was released a few weeks before the workshop. NASA recognized the need to update the roadmap to reflect the new decadal survey, but they did not feel this would substantially change the technologies in the roadmap. Even without pull from specific future missions, NASA indicated that they would pursue the same technology list to ensure that current technology would stay ahead of potential communication and navigation demand. The discussions mostly focused on the challenges for deep-space (interplanetary) communication and navigation, though some near-Earth-space solutions for optical communication repeaters were described. NASA outlined the issues for each of the level 2 WBS subareas: optical communication and navigation; RF communication; internetworking; position, navigation, and timing (PNT); and revolutionary concepts. Within each subarea, the presentation described the current state of the art, recent advancements, desired future developments, and mission-level impact. Challenges identified include laser pointing and stabilization (optical communication subarea), communication through challenging RF environments such as rocket plumes and reentry ionization (RF communication), utilizing arrays of antennas to increase the effective aperture (RF communication), onboard computing’s mass/power/volume constraints as they relate to onboard routing (internetworking), and autonomy for navigation (PNT). NASA mentioned that the integration of optical communications and disruption-tolerant networking (DTN) offers combined benefits that are stronger than each one alone. The DTN program is structured around near-term improvements in single-hop DTN, which will demonstrate benefits to automation rather than networking. Rather than scripting data transfers with manual downlink plans, DTN would allow for this to happen automatically onboard the vehicles. This provides a motivation for DTN even without a vision for a deep-space multi-node network of relays. After NASA’s presentation, a brief discussion period allowed the panel and interested members of the general public to ask questions of the NASA presenters. There were questions about the composition of future missions in the latest roadmaps, internetworking simulators, deep-space infrastructure for internetworking, networking interoperability/compatibility with international partners, technologies and architectures for space-to-ground opti - cal communications, technology hurdles for pinpoint landing, and prioritization/linking of technologies within the roadmap. Briefing 1: Satellite Networking Eylem Ekici (Ohio State University) provided a brief background of his work in wireless communication net - works, wireless network analysis and modeling, and protocol development. His comments on the TA05 roadmap focused primarily on the internetworking section. He stated that the roadmap captured the most important existing projects and test cases, but also emphasized the room for growth in this subarea. He believes there is significant
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178 NASA SPACE TECHNOLOGY ROADMAPS AND PRIORITIES potential for research and development in space-based networking, which can take advantage of terrestrial improve- ments in autonomous network operations for ad hoc mesh networks. Ekici identified disruption tolerant networking as the most critical challenge and a game-changing capability within the roadmap. However, he feels that existing work on DTN is insufficient to address needs of actual space missions due to poorly partitioned objectives, assets, functions, and interoperability. In addition, he believes that work on adaptive network topology should be a part of a forward-looking vision for networking, including work on requirements analysis, general network architectures, and protocol and solution development. While he felt that information assurance was important for medium-term applications, existing solutions (or new solutions developed by other agencies) are likely to address about 90 percent of NASA’s challenges at very low cost to the agency. In the question and answer session following his presentation, there were questions about the suitability of space-qualified, radiation-hardened electronics for networking applications. Existing commercial and government hardware typically have issues with radiation including single event upsets and latchups. Because NASA deep space missions operate in a much higher radiation environment than missions in LEO and GEO, there may be hardware-based challenges to implementing space networking solutions. Ekici indicated that there are likely to be hardware/processing issues that will have to be addressed, and recommended that this work occur in parallel with the networking and protocol development. Briefing 2: Optical Communications Gary Swenson (University of Illinois at Urbana Champaign) followed Ekici’s presentation with a discussion on observations generated by himself and a group of professors at UIUC with backgrounds in fiber lasers, quan - tum electronics, and optical remote sensing. Based on the background of the involved professors, this assessment focused on TA 5.1 Optical Communication and Navigation. They identified laser transmitters as a key challenge for optical communication, including desired improvements in weight, reliability, and efficiency. Secondary chal - lenges in this area are laser beam expanders, the uniformity of the beam in single mode, and methods for mitigat - ing atmospheric disturbance of the beam. For high bandwidths, sensor efficiencies, dark current (cooling), and amplifiers are all areas recommended for improvement. As a technology development effort, Swenson recommended that NASA address methods to extend the life - time of optical communication components, including reducing susceptibility to damage by energetic particles and reducing fiber degradation/darkening over time. However, Swenson also stated that NASA’s highest near- term priority should be performing an in-space demonstration of optical communications systems, rather than component-level improvements in apertures or atmospheric turbulence mitigation. Swenson also identified optical communications as low risk, but during the discussion period he clarified that this was low risk for near-term demonstration objectives. For long-term objectives with very large receivers, NASA needs to better understand the sensitivity and efficiency issues before a realistic assessment of the development risk can be made. There was additional discussion about the need for a local sync for generating path lengths between optical arrays on the ground. NASA indicated that they had some discussion on this subject while generating the roadmap, but the technical details were not addressed in the roadmap document itself. This was recognized as an area that will require additional simulation before an appropriate assessment of risk can be made. Briefing 3: Guidance and Control Mimi Aung (JPL) presented an assessment of TA05 from a guidance, navigation, and control perspective. She identified four classes of next-generation missions that will drive improvements in guidance and control: (1) precision landing for large bodies (reducing the landing error ellipse, autonomous safety); (2) landing on small bodies and primitive bodies; (3) formation flying (including swarms and distributed clusters); and (4) autonomous rendezvous and docking. Together, these missions will drive the need for onboard autonomous target-relative GN&C, multiple- spacecraft GN&C, and onboard target-relative navigation sensors. In all of these, target-relative navigation was identified as a key technology challenge. Aung indicated that improvements in GN&C will stress current onboard
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179 APPENDIX H computing elements, and recommended that NASA invest in advanced computing (including multi-core processing and field-programmable gate arrays, or FPGAs) to keep pace with the demand for additional processing. Aung stated that improvements in this area will require both subsystem and system demonstrations, includ - ing development and utilization of ground-based integrated testbeds and on-orbit demonstrations. Currently, each mission has to develop its own testbed; future efforts could focus on developing an open-architecture adaptable hardware-in-the-loop integrated testbed which could be re-used for multiple applications. Aung also mentioned that JPL feels that the integration of individual technology pieces into a high-functioning system will be a challenge on par with individual technology developments. JPL believes that an integrated test of precision EDL should be a higher priority than advancement of specific pieces. (This echoed the importance of system-level testing from Swenson’s previous presentation.) Several other workshop participants echoed this response, emphasizing the possible advantages of moderate-performance technologies that work well when integrated over the absolute best component technology. However, other comments from the public described a desire to focus the roadmap on technologies that OCT could bring to TRL 6, rather than integrated capabilities that were more program-specific (e.g., radiation-hardened FPGAs rather than terrain-relative navigation (TRN)). TRN as a discipline is more important for NASA to invest in, but each mission will still require substantial customization for their applications and operational concepts, which limits the effectiveness of investments in general TRN capabilities. Similarly, other public comments recommended that general-purpose testbeds could be developed by the programs/missions, rather than an independent technol - ogy program. The panel pointed out that science missions are focused much more on science than on technology, and are not generally interested in spending limited program resources on technology maturation. If the testbed or general-purpose research is not funded by a technology organization, the science program is unlikely to do it. Aung recommended adding a new section to the roadmap dedicated to autonomous integrated GN&C. This led to significant discussion on this approach, and highlighted the need to address the topic of GN&C in an integrated fashion. Currently, navigation is carried under TA05, but guidance and control is split between TA04 (Robotics, Tele-Robotics, and Autonomous Systems) and TA09 (Entry, Descent, and Landing). Briefing 4: X-Ray Navigation Darryll Pines (University of Maryland at College Park) described the X-ray NAVigatation and Autonomous Position (XNAV) program that he ran while he was at DARPA from 2003 to 2006. This presentation focused on only one technology: 5.6.1 X-Ray Navigation. Pines described the motivation for using pulsars as navigation beacons, and described potential accuracies of 24 to 36 meters in Earth orbit for long-duration observations, and accuracies less than a kilometer at other locations in the solar system. Newly researched navigation algorithms can provide accurate along-track solutions using the measured Doppler delay in the X-ray pulses. According to Pines, XNAV offers benefits over GPS due to the higher theoretical accuracy from short wavelengths (with appropriate clock updates from the ground), utility throughout the solar system, inherent radiation hardening, and robustness to radiation damage, jamming, and contamination. Because of these benefits, there have been several follow-on programs including the X-ray Timing program at DARPA and several smaller NASA programs. One drawback of XNAV is that past systems required instruments on the order of a few square meters in cross-section and approxi - mately 25 to 50 kg in weight. Recent developments, however, have improved detector signal-to-noise sensitivity and reduced the size, weight, and volume of prototype navigation instruments. Nevertheless, greater position and attitude accuracy will require improvements in X-ray photon detection and optics to produce instruments small enough for deep space navigation. Briefing 5: Deep-Space Navigation Lincoln Wood (JPL) provided a briefing with comments on specific sections of the roadmap that impact accuracy and performance of deep space navigation. Wood assessed the roadmap as conservative in estimates of deep space navigation accuracy for single antenna applications (e.g., line-of-sight Doppler and ranging) as well as multi-antenna applications (very long baseline array). In addition to new technologies related to frequency and
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180 NASA SPACE TECHNOLOGY ROADMAPS AND PRIORITIES timing, Wood stated that advancements in SWAP for existing capabilities/components should be technologies in themselves, and should be reflected in the roadmap alongside new capabilities. He stated that any game-changing capability would likely result from evolutionary advances with existing technologies, rather than revolutionary technologies. Wood’s assessment of the top technical challenges (within the frequency and timing section of the roadmap) include improvements in high-performance clocks (stability, SWAP, and reliability), oscillators, and space quali - fied lasers. These imply high-priority technology advancements in (1) improving frequency and timing reference sources by advancing the TRL, making SWAP advancements, and improving reliability, and (2) making reliability and SWAP improvements (rather than improving performance) for optical metrology hardware. Mercury ion atomic clocks were identified as a component technology near a tipping point, and neutrino navigation was identified as unfeasible on any kind of realistic development timescale. During the question and discussion phase, Wood recommended that NASA place navigation beacons around places of interest and locations that will be visited at higher frequencies, such as the Moon, Mars, Titan, and other locations. Briefing 6: Mission Design and Navigation Alberto Cangahuala (JPL) provided inputs on the roadmap’s treatment of navigation for lunar and interplan - etary applications. In this area, Cangahuala identified top technical challenges as: (1) high-fidelity modeling to mitigate the impact of long round-trip light times on numerical precision, (2) reducing onboard resources (mass, power, and delta-V) required for guidance and navigation, and (3) boot-strapping required to accrue necessary detailed environmental characterization information for target bodies. He also identified several trends for modern navigation systems, including the challenges of route planning for low-thrust systems, low-energy transfers, prox - imity operations, satellite and planetary tours, and operations in unstable and/or unknown dynamical environments. As a result of these trends, modern missions require a stronger integration of flight path and attitude control (i.e., coupling of control knowledge and thrust), highlighting the need for more onboard autonomy (both fully integrated systems and navigation “apps” that take advantage of existing flight system capabilities). Cangahuala identified mission/trajectory design as a potential technology gap in the roadmap. This is a cross- cutting capability with parts in modeling and simulation and navigation. Navigation and mission/trajectory design are connected by a common need for consistent modeling for planetary and spacecraft dynamics, and mission/ trajectory design can minimize navigation uncertainties as part of a design process. Within this field, high-priority challenges include improving the speed, agility, and robustness of trajectory optimizers and investigating new trajectory mechanisms (e.g., invariant manifolds, cycler trajectories). Public Comment and Discussion Session The following are views expressed during the public comment and discussion session by either presenters, members of the panel, or others in attendance. • Synergy with DOD investments. Some technologies in the roadmap may be synergistic with elements in the DOD. This includes a near-term experiment on atmospheric dynamics, knowledge about space-based IP-networking (though information assurance is a challenge), specific TWTA and SSPA component technologies, and minimization of SWAP for existing technologies. While some of these were tied to the now-cancelled TSAT program, other efforts in these areas are ongoing. NASA and DOD may benefit from working together on these technologies, or at least remaining cognizant of developments made by the other organization. NASA was encouraged to participate in the Space Industrial Council’s Critical Technologies Working Group, which addresses inter-agency technology development efforts. This could be a mechanism for NASA to communicate with their DOD counterparts and identify high-TRL develop - ment items that NASA could productize to claim early successes for OCT.
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181 APPENDIX H • International involvement. Based on a question about international cooperation, a representative from NASA OCT clarified that the near-term focus of the NRC is prioritization of the technologies, regard - less of who matures them. At some point in the future, OCT will address the potential overlap between NASA’s priorities and other organizations, but this will not be part of the NRC’s charter. • Systems engineering framework. A workshop participant stated that the roadmaps illustrate component technologies, but lack a systems engineering framework to identify synergies between technologies (espe- cially between different roadmaps). OCT responded that they will do this kind of strategic integration over the next 12 months, and that the NRC is not being asked to do this. • Technology pull from future missions. There was some discussion about how realistic the missions in the roadmap were. Many of the target missions may not be funded, and may not have high enough priority to become real. Participants discussed the value of using a more realistic assessment of potential missions, so that a better rationale for market pull (versus technology push) can be identified. • Industrial base. For navigation components (e.g., fiber-optic gyros, atomic clocks), there are potential industrial base/market size issues that may drive NASA toward a particular solution. There are only a few vendors in these areas, and some are not doing well and could strongly benefit from NASA developmental funding.