– A newly released study of the Pentagon’s planned Space Radar satellite constellation provides new ammunition to lawmakers who believe program officials have not placed sufficient priority on the development of the data-processing technologies needed for the system, according to a congressional source.


The study, prepared by the nonpartisan Congressional Budget Office (CBO), said Space Radar will be an improvement over existing imagery-collection systems but it also raises questions about Space Radar’s likely effectiveness in tracking movement on the ground. The study also said huge amounts of data collected by the Space Radar will heavily tax the
military’s satellite communications infrastructure, both existing and planned.


The Space Radar, a joint effort of the U.S. Air Force and National Reconnaissance Office (NRO), has long been hailed as a boon to military operations, largely because it would be able to detect moving targets on the ground, such as mobile missile platforms like the Iraqi Scud launchers that proved elusive during the 1991 Persian Gulf War. According to the CBO study, however, 35 to 45 satellites would be required for the system to have a 95 percent probability of locating a mobile platform following a missile launch. Once the launch platform has moved, which the study assumes would happen about five minutes after it fires its weapon, it would be virtually impossible to distinguish from other vehicles operating in the area, the study said.


The CBO study, “Alternatives for Military Space Radar” and dated January 2007, examined the relative effectiveness of four different systems: constellations of five, nine and 21 satellites, each equipped with a 40-square-meter sensor aperture; and a constellation of nine satellites, each with an aperture measuring 100 square meters. For the purposes of the study, the nine-satellite system was considered to be the reference constellation.


The report, requested by Sens. Wayne Allard (R-Colo.) and Bill Nelson (D-Fla.) back when they were serving as chairman and ranking member, respectively, of the Senate Armed Services strategic forces subcommittee, makes no recommendations.


The Space Radar’s effectiveness as a moving target detection and tracking system has been questioned before in report language accompanying various defense bills. The CBO study, based on unclassified sources, reinforces that language and makes a strong argument for allocating more resources to developing ground-based data-processing technologies necessary for moving-target detection, even if that comes at the expense of the space segment, the congressional source said.


Space Radar program officials, meanwhile, said the satellite designs evaluated in the CBO are larger, heavier and more challenging than the system designs being considered by the program office. In a written statement provided by Air Force spokeswoman Maj. Regina Winchester, these officials further noted that the CBO study did not evaluate Space Radar performance in conjunction with other air, space and ground sensors.


“Our analysis of alternatives showed that a more modestly sized Electronically Steered Array used in concert with other air, space and ground sensors is a better and more affordable option to meet the requirements than the isolated, stand-alone, larger arrays CBO studied,” the statement said.


The Air Force and CBO also disagreed on the Space Radar’s likely cost.


According to the study, the 20-year life-cycle cost of a nine-satellite Space Radar system would range from $35 billion to $52 billion. “The high estimate takes into account the cost growth that has commonly occurred for other space-based systems of the Department of Defense,” the CBO study said.


The Space Radar program officials said their estimates show a nine-satellite system costing between $20 billion and $25 billion. “To meet this estimate, the Integrated Program Office is committed to using a conservative, phased acquisition strategy that heavily emphasizes systems engineering during the early phases of development,” the officials said. “…We’re focused on maturing and proving technology through demonstrations and experiments using a mix of air, ground and existing space assets to reduce technical and cost risks.”


The CBO study had positive things to say about the planned Space Radar’s ability to collect static imagery. Currently the intelligence community and the military rely on classified satellites operated by the NRO for this type of data, but the Space Radar is expected to take over this collection task once it is in operation. The Space Radar is supposed to start launching in 2015.


According to the report, the Space Radar will be able to collect imagery at resolutions as sharp as one-tenth of a meter. The CBO also said that while none of the constellations it studied would be able to provide continuous coverage of a given region, “the response times of those constellations should be better than current systems can achieve.”


The report did not specify whether the expression “current systems” was a reference to the NRO’s radar satellites, the number and capabilities of which are classified. Generally speaking, the amount of imagery that could be collected by the Space Radar would be proportional to the number of satellites in the constellation, the report said.


For the moving target detection and tracking mission, the picture is murkier, with capabilities dependent in part on unknown variables such as advances in technologies and data-processing techniques; the size of the moving objects; their speed; and the background terrain. The study assumes that so-called space-time adaptive processing techniques would be used for moving-target detection. Since this is a relatively new technology, the study has scenarios: aggressive, in which the processing technique is assumed to be performing at or near its theoretical limit; and conservative, which assumes practical limitations will be encountered.


The slower a target moves, the more difficult it is to track, the CBO study said. Under the conservative scenario, the CBO concluded that the reference constellation would be in position to detect objects moving at 5 meters per second less than 5 percent of the time. For objects moving at 10 meters per second, that figure rises to about 20 percent. Under the aggressive scenario, the velocity of the object makes little difference: the reference system would detect objects moving either 5 or 10 meters per second about 30 percent of the time, the study said.


None of the notional Space Radar constellations examined by the CBO would be able to track any object for more than five to six minutes. “In the absence of other surveillance systems, those track lives are generally too short for a target to be attacked because they are unlikely to provide enough time for strike aircraft to locate a target,” the study said.


The area that the constellation could scan for large-scale movements of troops is far wider than for smaller objects such as trucks, the study said.


Adding to challenges inherent in the time-sensitive task of moving-target detection is the vast amount of data that must be processed and transmitted to the ground, the study said. To conduct wide-area searches at high resolutions, for example, the Space Radar would have to downlink data at rates that exceed the capacity of the military’s planned Transformational Satellite communications system, the study said.


The congressional source said the burden Space Radar would place on military communications satellites was perhaps the most alarming aspect of the CBO report. The staffer said the Air Force’s plans to delay the first Transformational Satellite launch until 2016 make little sense given that the Space Radar is supposed to begin launching a year earlier.