TOPIC: O1 Space Communications

• Highly phase-stable RF ground systems are critical to high accuracy radiometric tracking. Present systems rely upon analog transmission over 0.5 to 10 km distances of a broadband (100 - 600 MHz) spectrum. Transmission induced phase errors could be greatly reduced by developing highly phase stable digital sampling and time tagging systems that can be placed near (~10m) to the RF feedhorn without measurably degrading the RF signal capture with spurious tones and noise. Phase stability goals are given above. The sampler should Nyquist sample the 100 - 600 MHz band with at least 8-bit resolution and be capable of digitally transmitting the resulting samples over fiber optic lines;
  
• The VLBI parameter estimation software used to build the radiometric reference frames used for precise tracking relies on a Square Root Information Filter that makes use of Householder transformation techniques. These solutions often take several days of CPU on a modern workstation. Block matrix techniques have the potential to optimize the interaction of the CPU and cache memory thereby greatly reducing the CPU time needed for solutions. The goal is a factor of three improvement in total solution time for problems with 7 million data points and 500,000 parameters, which include at least 5000 parameters that are active over the entire data set;
  
• Microwave radiometry of atmospheric emission lines (22 GHz H₂O, 60 GHz O₂) has been successful in demonstrating 1 mm level calibration of tropospheric path delay. However, the usefulness of this technique has been limited by the large mass and size of the instrument packages. Identifying/developing low mass, low cost implementations of this technique without significantly sacrificing accuracy would greatly enhance precise tracking;
  
• Develop low mass, (Less than 1 kg) low cost onboard radio frequency standards for generating highly phase-stable onboard radio signals which achieve Allan standard deviations of 1 x 10^-15 at 1000 seconds and drift of less than 10^-15/day;
  
• Develop innovative tracking technologies using new wavelengths (X-ray, Infra-red, etc.), such as systems using celestial and planetary emissions and reflections (not limited to the visible spectrum) that can produce three-dimensional absolute and relative position and velocity in regions where Earth-based GPS measurements are not available, The technologies can exploit either ground based or on-board techniques;
  
• Develop innovative technologies for improving the state of the art in terms of cost and performance in making spacecraft-to-spacecraft measurements, such as omni-directional range and bearing sensors and robotic-vision-based systems; and
  
• Develop innovative navigation algorithms and software supporting analysis, design, and mission operations that will reduce operations costs and support multiple systems in simultaneous, tightly-coupled, non-quiescent operations, such as robotic servicing and formation flying.
  

• Low power consumption;
  
• Low mass/volume;
  
• Compliance with range safety standards;
  
• Flexible tracking loop programmability;
  
• Programmable output formats; and
  
• Operability in high G environments.
  

• Minimizing the life-cycle cost of an array that produces a given EIRP by selecting the optimum combination of antenna size, transmitter power, and number of antennas. This becomes much more difficult if the option of using the same antenna for both uplink and downlink is considered;
  
• Identifying/developing low-cost, highly reliable, easily serviceable components for key systems. This could include highly integrated RF and digital signal processing electronics, including mixed-signal ASICs. It could also include low-cost, high-volume antenna manufacturing techniques. (For the receiving array, another key component is a cryogenic refrigerator for the 15 - 25K range.) Also, low-cost transmitters (including medium-power of the order of 100s of Watts) amplifiers are key;
  
• Phase calibration techniques are required to ensure coherent addition of the signals from individual antennas at the spacecraft. It is important to understand whether space-based techniques are required or ground-based techniques are adequate. In general, a target spacecraft in deep space cannot be used for calibration because of the long round-trip communication delay;
  
• Design of ultra phase-stable electronics to maintain the relative phase among antennas. These will minimize the need for continuous, extensive and/or disruptive calibrations;
  
• Understanding the effect of the medium (primarily the Earth's troposphere) on the coherence of the signals at the target spacecraft. Generally, turbulence in the medium tends to disrupt the coherence in a way that is time-dependent and site-dependent. A quantitative understanding of this is needed; and
  
• Techniques for integrating a very low-noise, cryogenically-cooled receiver with medium power (1W to 200W) transmitter. If transmitting and receiving are combined on the same antenna, the performance of each should be compromised as little as possible while maintaining low cost and high reliability.
  

• Multiple waveforms and multiple channel support strive to reduce radio count to reduce power consumption of the overall communication system. Tradeoffs in radio count and radio complexity are considered in the analysis. Reconfiguration for software and firmware upgrades shall provide access control, authentication, and data integrity checks for the reconfiguration process. Partial reconfigurable logic allows simultaneous operation and upload of new waveforms or functions. Upon operator or automated load detection failure, capability to provide access back to a known, reliable operational state is needed. An automated restore capability ensures the system can revert to a baseline configuration, thereby avoiding permanent communications loss do to an errant reconfiguration process. Approaches should minimize size and power consumption for deep space transceivers incorporating fault tolerant, reprogrammable digital signal processing devices.
  
• Implementations demonstrating the concept function, and benefits of dynamic or distributed on-board processing architectures to provide maximum reconfigurability and processing capacity are sought. A common processing system capacity for communications, science, and health monitoring is envisioned.
  
• Demonstration of adaptive modulation and waveform recognition techniques are desired to provide capability to reconfigure to the waveform identified based on an on-board library or enable new waveform upload to the on-board library from the ground.
  

• Development and demonstration of low overhead, low complexity hardware and software architectures to enable software component or design reuse, or common testing standards that demonstrates cost or time savings. Emphasis on the application of open standards architecture to facilitate interoperability among different vendors to minimize the operational impact of upgrading hardware and software components.
  
• Methods that enable portability among reconfigurable logic hardware devices among different vendors, different device families and types of digital processing technologies.
  
• As the use of software and firmware increases with more flexible and portable software defined radio technologies, methods are sought to reduce the complexity and cost to space qualify and verify software operation for use in space yet maintain or increase on-orbit reliability.
  
• Techniques to ensure reliable software execution and failure detection and self-correction.
  
• One promise of a software defined radios is software and design reuse maintained in a common repository. The cost or ability to reuse software depends on implementation, development practices, code complexity and other circumstances. This subtopic seeks the development and demonstration of software tools or tool chain methodologies to enable both design and software code reuse.
  

• The use of reconfigurable logic devices in software defined radios is expected to increase in the future to provide reconfigurability and on-orbit flexibility for waveforms and applications. As the densities of these devices continue to increase and feature size decreases, the susceptibility of the electronics to single event effects also increases. Novel approaches to mitigate single event effects caused by charged particles are sought that reduces power consumption and complexity compared to traditional approaches (i.e., voting schemes and constant updates (scrubbing)).
  
• Techniques and implementations to provide a core waveform capability within the software defined radio in the event of failure or disruption of the primary waveform and/or system hardware. Communication loss should be detected and core or "gold" waveform automatically executed to provide control access to diagnosis system and over-the-air reload operational waveform and control software.
  

• Innovative solutions to provide software defined radio implementations to reduce power consumption and mass. Solutions should promote modularity and common, open interfaces.
  
• Software defined radio implementations that enable future hardware scalability among different mission classes (e.g., low rate deep space to moderate or high rate near planetary, or relay spacecraft). Operational characteristics range from 1's to 10's Mbps at UHF and S-band frequency bands up to 10's to 100's Mbps at X, and Ka-band frequency bands.
  

• Advancements in analog-to-digital converters or digital-to-analog converters to increase sampling and resolution capabilities while reducing power consumption.
  
• Novel techniques to advance memory densities, reduce power consumption, and improve performance in harsh environments.
  
• Advancements in reconfigurable logic technology including processing advancements, radiation hardened commercial technology and advancements in advanced computing such as polymorphous computing.
  

• Dramatic reduction of mass;
  
• Dramatic reduction in power requirements;
  
• High selectivity components, reducing interference and overlap;
  
• High reliability through Fault Tolerant design;
  
• Frequency agility;
  
• Software defined waveforms and modulation/demodulation.
  

• Innovative methods of using X-ray or radio pulsar signals for precise navigation or positioning of spacecraft. Small, low mass, reliable detectors, improvements in position accuracy, digital signal processing advances for time of arrival, drift estimation, and position estimation.
  
• Development of nano-scale communication devices and systems (e.g., FET arrays, nano-antennas, nano-transceivers, etc.) for nano-spacecraft applications.
  
• Quantum entanglement or innovative breakthroughs in quantum information physics to specifically address curious effects and critical unknowns relevant to revolutionary improvements in communicating data, information or knowledge between independent entities across space-time. Methods or techniques that demonstrate extremely novel means of effectively packaging, storing, encrypting, and/or transferring information or knowledge.
  
• Breakthrough power-efficiency in communications brought about through the use of natural phenomenon, e.g., soliton pulse/wave/energy propagation.
  
• Innovative uses of radiofrequency spectrum, planetary atmospheres, or planetary electromagnetic properties for the breakthrough communication of data, information or knowledge directly between independent entities.
  
• RF Micro Electro-Mechanical Systems (MEMS) devices. Besides low spatial volume, lightweight, and low-power consumption, these devices are also attractive to operate as high Q components and perform frequency selectivity - namely, agile pre-selectors, multi-couplers, and diplexers. Selectivity, or Q, for band pass filters currently comes at an unacceptably high penalty in size and mass. For example, most high rejection diplexers for space-based radios are almost as enormous as the modern radio package itself. To build and design high performance, tightly coupled, low volume space radios, compact selectivity-determining devices are a critical enabler. Most high Q filters above 400MHz, such as inter-digital filters and others involving resonant cavities, are wholly mechanical assemblies which can be "folded" in their design and lend themselves to micro machining techniques.
  
• Other rich areas of investigation may lie within the area between MEMS and Micro-Machined devices, including electromechanically tuned filters, 3D micro machined RF resonators, filter configurations consisting of cantilevered structures, as well as carbon nano-tube waveguides. Develop, apply and demonstrate advantages of RF MEMS circuitry that proliferate the implementation of next-generation lightweight communications systems (e.g. extravehicular activity (EVA) radios).
  

• Space-qualifiable, efficient (greater than 25% wall plug), lightweight, variable repetition-rate (1 - 60 MHz), tunable (± 0.1 nm) pulsed 1064 nm transmitter sources (diode-pumped fiber amplifier or bulk crystal laser/amplifier) with greater than 1 kW of peak power per pulse (over the entire pulse-repetition rate), and greater than 10 W of average power, and narrow (< 10 pm) spectral width;
  
• Space-qualifiable, high-peak power (> 1.2 W), average-power (> 300 mW), operating wavelength less than 1000 nm single-mode-fiber pigtailed laser diode transmitters (includes necessary modulator; internal or external driver) with narrow spectral width (< 100 pm) supporting 4-ary pulse-position-modulation for data rates of 0.5 - 1000 Mbps with high wall-plug electrical-efficiency (> 25%);
  
• Space-qualifiable, photon counting 1064 nm and/or 1550 nm detectors a temperature of 220 K or greater, with the gain greater than 3000, detection efficiency greater than 50%, dark rate < 1 MHz per mm² active area, > 0.2 mm in active area diameter, bandwidth greater than 500 MHz, saturation levels > 50 Mcounts/s and non-gated (continuous operation), and lifetime > 3 years at 100 Mega photons /sec continuous photon flux;
  
• Lightweight, compact, high precision (less than 0.1 micro-radian), high bandwidth (0-2 kHz), inertial reference sensors (angle sensors, gyros) for use onboard spacecraft;
  
• Novel schemes for stray-light control and sunlight mitigation, especially for large (> 5 m) ground-based optical telescopes that must operate when pointed to within a few (about 3) degrees of the Sun;
  
• Lightweight, high precision (one micro-radian accuracy) star-trackers for spaceflight application that can be integrated with an optical communications terminal;
  
• Novel techniques and technologies that will enable very low cost, large aperture (> 5 m equivalent aperture diameter) telescopes for ground or space-borne use;
  
• High power ground-based, relatively low-cost diode-pumped laser technology capable of reaching 100 kW average power levels in a TEM₀₀ mode, for uplink to spacecraft;
  
• Artificial laser guide-star and beam compensation techniques capable of removing all significant atmospheric turbulence distortions (tilt and higher-order components) on an uplink laser beam;
  
• Novel techniques to reduce the development cost and risk of future space-borne optical communications transceivers (e.g., automatic focusing or alignment techniques); and
  
• Systems and technologies relating to sub-microradian pointing, acquisition, and spacecraft vibration.
  

• Ultra-small, low-cost, low-power, modular deep-space transceivers, transponders, and components, incorporating MMICs and Bi-CMOS circuits;
  
• MMIC modulators with drivers to provide large linear phase modulation (above 2.5 rad), high-data rate (10 - 200 Mbps), BPSK/QPSK modulation at X-band (8.4 GHz), and Ka-band (32 GHz and 38 GHz);
  
• High-efficiency (> 70 %) Solid-State Power Amplifiers (SSPAs), of both medium output power (10 - 50 W) and high-output power (150 W - 1 KW), using power combining techniques and/or wide-bandgap semiconductor devices at X-band (8.4 GHz) and Ka-band (32 GHz and 38 GHz);
  
• Traveling Wave Tube Amplifiers (TWTAs), SSPAs, modulators, and MMICs for 26 GHz Ka-band (lunar communication);
  
• TWTAs operating at millimeter wave frequencies and at data rates of 10 Gbps or higher;
  
• Ultra low-noise amplifiers (MMICs or hybrid) for RF front-ends (< 50 K noise temperature); and
  
• MEMS-based RF switches and photonic control devices needed for use in reconfigurable antennas, phase shifters, amplifiers, oscillators, and in-flight reconfigurable filters. Frequencies of interest include S-, X-, Ka-, and V-band (60 GHz). Of particular interest is Ka-band from 25.5 - 27 GHz and 31.5 - 34 GHz.
  

• Low mass/power (100's of milliwatts) transceivers for very short range interfaces with sensors and other small devices to enable communications among humans, robots, and access network terminals;
  
• Reconfigurable, directionally selectable, steerable, multi-frequency switched patch or multiple-in multiple-out [MIMO] antenna arrays for human helmets, robots, and fixed structures (e.g. habitats);
  
• Miniaturized planar, omni-directional, dual-polarized, self-orienting, and sector antennas for surface-to-surface communications among mobile and fixed nodes;
  
• Low power space rated ASICs and FPGAs for wireless network products; short (< 1km) range access point, base stations, or wireless router bridges for extending surface network coverage;
  
• Fixed, long (up to 50km) range, wireless network terminals for extending high data rate communications over large distances;
  
• Integrated, autonomous tracking and navigation architectures and technologies;
  
• Self-healing, ad-hoc, disruption tolerant network protocols for intelligent, autonomous link management and reliable throughput.
  

• High rate, efficient solid state amplifiers capable of very high data rates over 1,000 - 10,000 km distances with ranging signal embedded;
  
• Very low power, data rate, and cost inter-spacecraft S-band transceivers for inexpensive spacecraft;
  
• Optical transceiver capable of very high data rates over 1,000 - 10,000 km distances;
  
• Agile, multi-beam antennas; mesh or other material flexible reflector unfurlable antennas for Ka-band and lightweight scanning phased array antenna systems;
  
• SEU and solar flare tolerant transponder capable of programmable wide carrier frequency range from S-band to Ka-band, taking GPS measurements, and handling IP at the digital level;
  
• Micro software radio technology for autonomous and intelligent space applications;
  
• Low mass, volume, power, and cost stable oscillators to provide accurate time and frequencies for autonomous operations;
  
• Autonomously reconfigurable receivers capable of automatic link configuration and management;
  
• Microwave ranging hardware built into communication system for rendezvous and collision avoidance;
  
• Ad-hoc, long-range spacecraft to spacecraft network protocols to set up links on demand such that each node can route data through to another node.
  

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