GPS experts suggest new approach for high-tech satellites
In a presentation to the National Space Based Positioning, Timing and Navigation Advisory Board, Bradford Parkinson, professor emeritus of aeronautics and astronautics at Stanford University and co-inventor of the GPS program, and Martin Faga, former director of the National Reconnaissance Office, said technological enhancements that the Air Force has asked for in the next generation GPS III contract raise the cost and the risk that the contract will miss deadlines. The advisory board reports to an executive committee whose members come from the departments of Defense, Transportation and Homeland Security, as well as other agencies.
Boeing and Lockheed Martin are competing for the GPS III contract, which the Air Force plans to award next year. The Air Force wants the winning bidder to develop satellites with an advanced space-based communications systems and powerful spot beams that will provide positioning and mapping services to a specific geographic area on Earth, according to a briefing by Thomas Powell, a GPS project engineer from The Aerospace Corp. and who works for the Air Force Global Positioning System Wing. Powell gave the briefing to the Civil GPS Service Interface Committee.
Parkinson and Faga told the advisory board that a 30-satellite constellation "is much more important than spot beams and wide-band cross links." They described the cost of such technology as reminiscent of the science-fiction technology seen in the television series Battlestar Gallatica. "Battleship Galactica or Affordable First Step?" they ask on a slide titled "Why Affordability Is so Critical."
The Air Force wants to put the advanced technology on the 27 satellites called for in the GPS III contract. (The current constellation is made up of 30 satellites, but it changes based on the age of satellites in orbit and the launch of new ones. Currently, Defense aims to maintain a 24-satellite constellation.) But Parkinson and Faga said the 27 satellites will not meet requirements for accuracy in mountainous terrain or urban canyons. In the mountains of Afghanistan, the GPS signal availability for U.S. troops is low, the two said. "Blindly pursuing all the current [GPS III] requirements would be expensive, risky and late," according to their presentation. "The complex satellites will threaten the schedule and ultimately the constellation size."
However, building smaller and more affordable satellites would reduce the total cost of the GPS III contract because two of the smaller, less expensive satellites could be launched at the same time in one rocket. Only one of the satellites equipped with the advanced technology could be launched at a time. Launching two satellites at the same time would save the Air Force as much as $50 million per satellite, Parkinson and Faga concluded.
Defense uses GPS for a wide variety of missions, including guidance of precision munitions and by ground troops with handheld receivers, and these missions would benefit from the improved accuracy provided by a 30-satellite constellation, Parkinson and Faga said.
They also reported that there is a need for a 30-satellite constellation to support the next generation FAA air traffic control system, called the Automatic Dependent Surveillance-Broadcast program, which derives its baseline navigation information from GPS.
Richard Day, FAA vice president for en-route and oceanic services, told the advisory panel that a 30-satellite constellation would provide accurate measurements of how far apart aircraft are during their landing approaches and while taking off.
Parkinson and Faga recommended that the Air Force put the simpler GPS III satellites under contract with an early delivery date, but that strategy looks problematic because the GPS III program is already missing deadlines. Air Force officials have said that securing certain approvals from the Pentagon, including demonstrating the technology works, have been postponed from August until December.
Air Force Maj. Patrick Ryder, a Defense spokesman, said the Office of the Assistant Secretary of Defense for Networks and Information Integration (ASD NII) will receive a briefing on the advisory board's reports Oct.18 and will give the pair's report "proper review and consideration."
Commenting on Parkinson and Faga's suggestion that Defense focus on development, Ryder said the office views it "prudent to build the most cost-effective space vehicles possible. That must be determined in evaluating bidder proposals against a government specification written to satisfy [Joint Requirements Oversight Council] validated requirements."