Discoverer II (DII)
The Air Force / NRO / Army Discoverer II program was to launch of two satellites to demonstrate tracking mobile (as opposed to fixed) targets on the ground. The FY2001 DOD appropriations (P.L. 106-259) and authorization (P.L. 106-398) acts terminated Discover II, and provided $30 million to NRO to develop and mature technologies for this purpose.
The Discoverer II (DII) program was an Air Force, Defense Advanced Research Projects Agency (DARPA),and National Reconnaissance Office (NRO) joint initiative. The program's title reflected the revolutionary objectives to be pursued in the proposed effort. Discoverer was the public cover name for the Corona program, which provided the first satellite imagery - a completely new capability.
The Discover II system was to be capable of generating very high resolution elevation data (1 meter post spacings) and highly accurate radar imagery. The preliminary list of demo objectives included 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 was to 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.
The DISCOVERER II constellation was to consist 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 answered 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 included 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.
- In strip map SAR mode, DISCOVERER II would provide 3 meter impulse response (IPR) imagery at a collection rate of 700,000 km2 per hour. Such collection would typically be used for object detection, to cue collection in other modes or using other sensors for classification and/or identification.
- In scan SAR mode, DISCOVERER II would provide 1 meter IPR imagery at a collection rate of up to 100,000 km2 per hour. Such collection would typically be used for object classification.
- In spot SAR mode, DISCOVERER II would provide up to 160 images per hour at 0.3 meter IPR of 4 km x 4km target areas. Such collection would typically be used for object identification
- In GMTI mode, DISCOVERER II would provide 3 meter target location error at a collection rate of 2,000,000 km2 per hour for object detectable velocities between 1.3 and 58 knots.
DISCOVERER II was to provide 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.
By the late 1990s the Services had equipped or were 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 included 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 possessed imagery subsystems, which the Defense Airborne Reconnaissance Office (DARO) 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 would 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
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