Discoverer II Technology

One of the key Defense problems involves the ability to locate and identify potential targets. This challenge has been quantified as the ability to search 40,000 square nautical miles per day with one meter resolution. This is equivalent to locating an object several meters in diameter in an area the size of a small country. For the purpose of this program we have artificially increased the resolution required for this application to provide a serious challenge for the Adaptive Computing researchers.

The problem can be simplistically divided into two categories, detection and identification. The detection problem is considered to be a bit-level problem while the identification is a byte-level problem. This analysis is based on techniques known as template matching. This granularity provides an interesting application for the dynamic and temporal reuse aspects of Adaptive Computing. The computation levels for this problem when the targets are partially obscured reaches the hundreds-of-teraflop range.

The government intended to support development of the tactical ground segment through risk reduction efforts in the areas of communication link studies, frequency management activities, 20/40 GHz space and ground communications technology development, ground processing and information infrastructure studies, and secondary dissemination interface specification.

Communication link studies focus on atmospheric and elevation dependent effects at the higher frequencies on area rates, revisit intervals, and system access. As ongoing studies are completed they would be added to the library. Frequency management activities resulted in preliminary frequency band recommendations, to be followed by detailed compatibility studies, final frequency recommendations, and frequency assignment filings, made in concert with Phase I contractors' input, by the first quarter FY00. Efforts for 20/40 GHz space and ground communications technology development were yet underway but were planned to study and develop space and ground transmitter technology, transmitter power management techniques, antenna feed technologies to support X, Ku and Ka in a single aperture, multi-rate modulator/demodulators, higher rate input/output technology in the TES/MIST interface, and other selected efforts to support the demonstration goals.

Ground processing and information infrastructure studies covered the CIG/SS, TES, MIST, and secondary dissemination interface specifications. Suitability of the Common Imagery Processor (CIP) and Modular Interoperable Surface Terminal (MIST) for the STARLITE Study Concept have been evaluated. The ground system evaluated for this effort was the Enhanced Tactical Radar Airborne Correlator (ETRAC) which is currently being migrated into the TES as part of the on-going P3I program.

Northrop Grumman evaluated the Common Imagery Processor [CIP] to determine the feasibility of the ground station architecture and the imagery processor viability to accept a higher density datastream from another source of unique operational characteristics, while retaining the capabilities inherent in the current configuration. In summary, it was determined the processor with appropriate system modifications, could be capable of handling the STARLITE satellite data processing and collection planning. Analysis of future server processing capabilities, applying Moore's Law, indicates the processing capability will likely exceed the DISCOVERER II objective constellation capabilities. Further evaluation is required to assess processing latencies, data formats, and other characteristics that will evolve from the space based radar design.

L3COM evaluated at the system level, those modifications to the ETRAC and MIST communication subsystem to support an increased downlink data rate of 548.352 Mbps also referred to as 2X from the STARLITE design. The MIST provided the antenna, RF electronics, modulator, demodulator and link controller that delivers the imagery data to the ground station. Several design options were identified for consideration to accommodate the increased data rate and further acknowledged the MIST is capable of accommodating a data rate up to 4X. Unknown was the cost impact to implement the 4X design and further analysis is needed to assess the maintainability and impact to operational capabilities. Additional work in the frequency allocation arena was needed and was pursued within the Discoverer II Joint Program Office.

Estimated navigation and timing accuracy requirements, minimum SNR requirement, and tasking constraints for high resolution, single-pass IFSAR collection were extrapolated from the performance and characteristics of airborne systems. Preliminary results were obtained from trade studies on terrain mapping modes (stereo SAR and IFSAR), orbit configurations for a satellite pair to allow monostatic and/or bistatic single-pass IFSAR operation, and performance, including coverage rates, latency, and mode availability.

The Government was to provide a requirements document describing algorithms and performance requirements (thresholds, goals and trades) for MTI/SAR/ECCM on-board/off-board processing. The specification includes HRR-GMTI Space Time Adaptive Processing (STAP), with subsequent target detection and multiple hypothesis tracking, including automatic target recognition. The package was to present results of theoretical analysis showing the dependency of minimum detectable velocity, bandwidth, classification accuracy, and revisit on track purity. The Government was to provide analysis results and phase history data from subsequent enhanced collections, including communications, A/D, and processor quantization effects, frequency jump burst (FJB) and stepped chirp effects, influences of two step nulling for ECCM, range sidelobe effects and as available, classification accuracy as a function of bandwidth and polarization. In this Government was to validate the processing algorithms using synthetic and actual targets, and man-made and natural clutter.

Trade studies to show the performance of stereo SAR and interferometric SAR modes in terrain mapping were completed in 1999. Orbit configuration trades studies were conducted to indicate system performance for alternative configurations, including coverage rate, latency, and mode availability. Initial version of error model were completed for high-resolution terrain mapping with proposed allocation of errors to individual error sources. Errors include navigation and timing errors, noise errors, and errors due to atmospheric and scene-based phenomena.