TOPIC: O1 Space Communications

• Software for transcoding of compressed bit streams from CCSDS Image Data Compression recommendation to commercial JPEG2k bit stream;and
  
• Demonstration in either PC-based or workstation-based systems with minimal loss of quality during the transcoding process.
  

• A design for a set of coded modulations operating at bandwidth efficiencies from 0.5 bits/symbol/Hz to 3+ bits/symbol/Hz, in steps of approximately 0.5 bits/symbol/Hz. Each point design shall require a bit signal-to-noise ratio not higher than 1 dB above the unconstrained-input, 2-dimensional capacity of the additive white Gaussian noise (AWGN) channel. The preferred input block frame length is 4K to 16K bits.
  
• Special emphasis is placed on a channel coding design suitable for near Earth missions, operating at least at over 80% coding rate with an error floor lower than Bit-Error-Rate (BER) of 10e-10, and encoder/decoder complexity consistent with implementations at data rates up to 1 Gbps. The new design, when compared with current CCSDS Reed-Solomon (255,223) coder at BER of 10e-5, should have over 2dB Eb/No gain. The preferred code block frame length is from 4K to 16K bits.
  
• High-speed implementation of the coded modulation suite with processing throughput close to 300 Mbits/sec and demonstration in test bed. The test bed shall include functions of encoding, modulation, demodulation, and decoding. The ability for the test bed to incorporate channel impairments, an over-the-air RF component, and software re-configurability, are desirable.
  
• RF receivers with symbol synchronizer providing soft-decision output over 8 bits/sample, as input to Maximum Likelihood Detector to provide metrics for decoding Trellis-coded-Modulation.
  

• 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 H₂0, 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.
  

• 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.
  

• Advancements in bandwidth capacity, reduced resource consumption, or adherence to standard and open hardware and software interfaces. Techniques should include fault tolerant, reliable software execution, reprogrammable digital signal processing devices;
  
• Reconfigurable software and firmware that provide access control, authentication, and data integrity checks of the reconfiguration process including partial reconfiguration, which allows simultaneous operation and upload of new waveforms or functions;
  
• Operator or automated reconfiguration, or waveform load detection failure, and the ability to provide access back to a known, reliable operational state. An automated restore capability ensures the system can revert to a baseline configuration, thereby avoiding permanent communications loss due to an errant reconfiguration process or logic upset;
  
• Dynamic or distributed on-board processing architectures to provide reconfigurability and processing capacity. For example, demonstrate technologies to enable a common processing system capacity for communications, science, and health monitoring;
  
• Adaptive modulation and waveform recognition techniques are desired to enable transceivers to exchange waveforms with other assets automatically or through ground control;
  
• Low overhead, low complexity hardware and software architectures to enable hardware or software component or design reuse (e.g., software portability) to demonstrate cost or time savings. Emphasis is on the application of open standard architectures to facilitate interoperability among different vendors and to minimize the operational impact of upgrading hardware and software components;
  
• Software tools or tool chain methodologies that enable both design and software modeling and code reuse, and advancements in optimized code generation for digital signal processing systems;
  
• 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 continues to increase, and size decreases, the susceptibility of the electronics to single event effects also increases. Novel approaches are sought to mitigate single event effects in reconfigurable logic caused by charged particles, thereby improving reliability. New methods may show advancements in reduced cost, power consumption, or complexity compared to traditional approaches (i.e., voting schemes and constant updates {e.g., scrubbing}).
  
• Techniques and implementations to provide a core 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 capability (e.g., "gold" waveform code) is automatically executed to provide access control and restore operation;
  
• Innovative solutions to software-defined radio implementations that reduce power consumption and mass. Solutions should enable future hardware scalability among different mission classes (e.g., low-rate, deep space to moderate or high-rate near planetary, or relay spacecraft) and should promote modularity and common, open interfaces; and
  
• In component technology, advancements in analog-to-digital converters or digital-to-analog converters to increase sampling and resolution capabilities; novel techniques to increase memory densities; and advancements in processing and reconfigurable logic technology, each reducing power consumption and improving performance in harsh environments.
  

• Use of 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 (e.g., quantum key distribution), and/or transferring information or knowledge in space-to-space or space-to-ground links;
  
• 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;
  
• RF Micro Electro-Mechanical Systems (MEMS) devices. MEMS devices have low spatial volume, are lightweight, and have low-power consumption, making them attractive to operate as high Q components and perform frequency selectivity (i.e., 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. At present, most high rejection diplexers for space-based radios are quite large. 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; and
  
• Other areas of investigation to consider 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. Development of RF MEMS circuitry that applies and demonstrates significant advantages that proliferate the implementation of next-generation lightweight communications systems.
  

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