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Discoverer II (DII)

The Discoverer II (DII) program is an Air Force, Defense Advanced Research Projects Agency (DARPA),and National Reconnaissance Office (NRO) joint initiative. The program is based on Defense Advanced Research Projects Agency (DARPA) work on a new lightweight satellite called STARLITE. The STARLITE concept was advanced in early 1997 following the completion of a DARPA-sponsored study. This study reported the feasibility of developing, deploying and operating a constellation of relatively inexpensive radar satellites designed to affordably provide near-continuous, day/night, all-weather, synthetic aperture radar (SAR) imaging support to the warfighter that could be directly tasked by the warfighter and directly downlinked to theater for processing and exploitation. Shortly thereafter, the concept was modified to incorporate a low cost approach to space-based High Range Resolution Ground Moving Target Indication (HRR-GMTI) collection as well as SAR imaging capabilities in response to Air Force interest in complementing the Unmanned Air Vehicle (UAV), U-2 and Joint Surveillance Targeting Attack Radar System (JSTARS) battlefield HRR-GMTI surveillance with near-continuous, deep-look HRR-GMTI coverage from space.

At the time STARLITE was proposed, the NRO was in the midst of defining its Future Imagery Architecture (FIA) intended to serve as the basis for acquiring the next generation of imaging satellite systems. The Department of Defense, the Directors of DARPA and the NRO asked the Defense Science Board (DSB) to establish a Task Force on Satellite Reconnaissance (the so-called “Hermann Panel”) to review the operational, technical, industrial and financial aspects of both the STARLITE and FIA initiatives. In January 1998, the DSB Task Force on Satellite Reconnaissance issued its report. The Task Force recommended that a modified STARLITE program be initiated, as a “Military Space Radar Surveillance Program,” in an effort to achieve broad-area, all-weather, near-continuous radar access that could be integrated with military operations.

In late February 1998 DARPA, the Air Force and the NRO signed a Memorandum of Agreement (MOA) establishing a joint program to undertake a “Space-based Radar Risk Reduction and Demonstration Program” and a Joint Program Office (JPO) to execute the program. In April the joint SBR HRR-GMTI/SAR demonstration program was designated Discoverer II. This new objective constellation of 24 satellites configured with Synthetic Aperture Radar (SAR) will allow for direct tasking control to a deployed Joint Task Force [JTF] tactical commander. The constellation would allow for a very rapid revisit rate (about 15 minutes) to most areas of the earth. The Discover II system would be capable of generating very high resolution elevation data (1 meter post spacings) and highly accurate radar imagery. The preliminary list of demo objectives include a determination of the feasibility and utility of delegated collection management authority to a tactical (i.e. joint task force) commander; and a demonstration of SAR data downlink using lightweight satellites. It will develop and demonstrate an affordable space-based radar (SBR) with High Range Resolution Ground Moving Target Indication (HRR-GMTI), Synthetic Aperture Radar (SAR) imaging capabilities and Digitized Terrain Mapping Elevation Data (DTED) that will provide reconnaissance, surveillance and precision geolocation support to the tactical warfighter.

On February 22, 1999, three contractor teams were selected for Phase One of the Discoverer II space-based radar technology demonstration program. The selected contractor teams are lead by Lockheed Martin Astronautics, Littleton, Colo., Spectrum Astro Inc., Gilbert, Arizona, and TRW Defense Systems Division, Redondo Beach, Calif. Each Phase One team has been awarded a firm, fixed-price, initial contract valued at about $10 million. A contract option is planned to complete the 18-month Phase One effort. The total Phase One effort is estimated at about $60 million. Each team will perform concept definition, system capabilities and performance trade studies, cost-performance trade-off analyses and preliminary system design. Phase One of the Discoverer II program will last about 18 months and allows the most promising contractor teams to complete preliminary prototype system designs. At the end of Phase One, one or two contractors will be selected to proceed to Phase Two to perform final design and fabrication of the two Discoverer II satellites.

Discoverer II is an R&D prototype demonstration program to identify and validate the technology growth path required to a launch a capability by 2008 [if full funding was approved, deployment of the additional 22 STARLITES was projected by DARPA for FY03-05]. Launches using GFE EELV or Delta II class launch vehicles are programmed for 4 th quarter FY 2003 and 1 st quarter FY 2004. The DISCOVERER II constellation consists of 24 low cost satellites, with a constellation constructed in 8 planes of 3 satellites evenly spaced per plane, in a Walker orbit with phase value 4 and inclination of 53 degrees, at 770 km altitude. By designing the orbitology this way, DISCOVERER II answers a commander's request for an imaging operation within fifteen minutes after receiving tasking, 90% of the time, averaged across 65 degrees north and south latitude.

Sensor characteristics include grazing angle of 12 degrees (6 degrees for ground moving target indication -GMTI), slope angle of 70 degrees, and squint angle of 45 degrees (no squint angle for GMTI). SAR collection can only occur in one "wing" of the "butterfly" ground coverage area at a time, antenna slewing is required to image in the other "wing." Synthetic aperture radar was selected to provide day/night all weather collection capability.

DISCOVERER II provides in-theater tasking capability to the services during training and exercises, and JTF and component commanders during crisis or hostilities using an Apportionment by Pass, Allocation by Operations methodology. Specifically, the JTF possesses the complete collection capability of the constellation for all those passes that will view the JTF Area of Operational Responsibility (AOR), once a contingency has been declared.

The Services have equipped or are in the process of developing Distributed Common Ground/Surface Systems (DCGSs), for receipt, processing, exploitation and dissemination of intelligence data from multiple sensors. These systems include the Navy Tactical Input Segment (TIS), Marine Corps Tactical Exploitation Group (TEG), Army Tactical Exploitation System (TES), and Air Force Contingency Airborne Reconnaissance System (CARS). Each of these possesses imagery subsystems, which the Defense Airborne Reconnaissance Office (DARO) has required to migrate toward commonality and interoperability under the Common Imagery Ground/Surface System (CIG/SS) initiative. Required elements for CIG/SS compliance include use of the CDL, the Common Imagery Processor (CIP), the Imagery Exploitation Support System (IESS), and the Imagery Product Library (IPL).

DCGSs supporting the JTF and/or air/ground/naval component commanders task and downlink satellites on each pass that views the AOR, with changes in tasking priority among the ground systems operating for the contingency potentially changing on each spacecraft pass.

For each 24-hour period of operations during a contingency, the JTF Commander apportions the collection capabilities according to the objectives for that day. For example, during the air campaign early in Desert Storm, the JTF may have apportioned 35 percent of passes (59) to the Air Component Commander, 35 percent (59) to the Naval Component Commander, 20 percent (34) to the Ground Component Commander, with 10 percent (16) reserved for JTF needs. In the days prior to movement of combined ground forces across the Iraq and Kuwait borders, the apportionment may have shifted to 20 percent (34) to Air, 20 percent (34) to Naval, 50 percent (84) to Ground and 10 percent (16) reserved for JTF. With a 24 satellite constellation, approximately 168 passes can view the Iraqi theater of operations during a typical day. Allocation by Operations provides for assignment of individual passes to specific ground systems directly supporting the JTF or a Component Commander based upon Component requests, considering their anticipated combat operations for a particular day. In the event that requests arrive from more than one component for a particular pass, the JTF J2 Collection Manager will adjudicate the priority between the two requests, based on the JTF Commander's mission priorities. Or the Collection Manager will require that the selected Component DCGS system that gets the pass provide primary imagery to the other Component's DCGS.

DCGSs that can also receive intelligence from multiple sources would use DISCOVERER II data complementary with those sources. This takes advantage of each sensor's unique strengths, maximizes efficiency and ensures truly synergistic operations. The result for JFCs is more responsive and timely battlespace information and greater employment efficiency for collection systems. DISCOVERER II radar data can be used to cue airborne sensors to provide dwell surveillance or airborne or national sensors for target identification and classification. National and airborne sensors can also cue DISCOVERER II collection of movement or stationary targets at high resolution. Cross-cueing can be highly valuable when other GMTI sensors have collection gaps in time and space, as in beyond line of sight or radar shadowed areas, or when adverse weather, diplomatic/political or airspace restrictions prevent other systems from flying.

DISCOVERER II SAR imagery taken over a period of several hours or days of a particular assembly area, when subjected to Coherent Change Detection processing, may show changes in levels of activity for forces based in that general locale. GMTI data will also indicate relevant military activity through indications of traffic flow and movement into and out of known or suspected areas of operation. This data would be used to cue unmanned aerial vehicles (UAVs) or other airborne and national sensors for vehicle/target identification and classification, for purposes of interpreting the opposing commander's intent. The DISCOVERER II high-revisit-rate feature, wide area coverage, and on demand assured access SAR capability could reduce the tasking on national and theater assets, to increase their effectiveness in collecting targets of a strategic nature.

Signals Intelligence (SIGINT) platforms may indicate a potential for vehicle movement into or out of a certain garrison location, or for the presence of high value assets. This information would be used to task DISCOVERER II GMTI coverage in the vicinity of the site to confirm or deny such movement, or to task DISCOVERER II SAR coverage to attempt to identify the characteristics of the hostile forces gathered at that location.

The Enhanced Tactical Radar Correlator (ETRAC) was planned by DARPA to support the demo as the ground processing segment, responsible for tasking, receiving the direct down link, processing, and exploiting the data. DARPA planned to cover the costs to include modifications to the ETRAC. The Government desires to leverage the migration path of the CIG/SS infrastructure, which employs the Common Imagery Processor (CIP) and Modular Interoperable Surface Terminal (MIST). The ground interface for the Phase II operational demonstrations will use CIG/SS compliant infrastructure resident in the Tactical Exploitation System (TES), and disseminated using existing infrastructure. It is anticipated the Phase II SI(s) will establish a relationship with the CIP prime contractor, Northrop-Grumman

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 slide is annotated with an estimate of the number of configurable devices that might be required to meet these requirements in 1996 and in 2000. These estimates present an overly optimistic view of the technology capabilities today because of the limited ability to deliver raw performance to an application. The 2000 goals in terms of component count remain a challenge for the community.

The government intends 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 will be added to the library. Frequency management activities have 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 are not yet underway but are 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 have 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 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 provides 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 is 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 is needed and is being 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 will be extrapolated from the performance and characteristics of airborne systems. Preliminary results will be 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 will 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 will present results of theoretical analysis showing the dependency of minimum detectable velocity, bandwidth, classification accuracy, and revisit on track purity. The Government will also 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 will 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 will be completed and results will indicate system performance for alternative configurations, including coverage rate, latency, and mode availability. Initial version of error model will be completed for high-resolution terrain mapping with proposed allocation of errors to individual error sources. Errors will include navigation and timing errors, noise errors, and errors due to atmospheric and scene-based phenomena.

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Maintained by Robert Sherman
Originally created by John Pike
Updated Monday, January 24, 2000 11:00:47 AM