WASHINGTON — The U.S. Air Force estimates it could save billions of dollars over time by revamping its current GPS plans, but the lowest-cost approaches come with the highest risk, the U.S. Government Accountability Office (GAO) said in a report released Sept. 9.

Moreover, the money-saving options identified by the Air Force, which include using smaller satellites and hosted payloads, would require up-front investments that are difficult to make in the current budget environment, the congressional watchdog agency said. The GAO also said the Air Force’s cost estimates were not sufficiently refined to support programmatic decisions.

“Although the Air Force report is a good starting point, more information on key cost drivers and cost estimates, and broader input from stakeholders would help guide future investment decisions,” a report summary said.

The report, “Global Positioning System: A Comprehensive Assessment of Potential Options and Related Costs is Needed,” was an evaluation of a separate Air Force study of GPS cost cutting options. Both the original study and the GAO’s critique were requested by Congress.

The Air Force study focused exclusively on the GPS space segment, which the GAO said accounts for more than half the cost of the service’s overall positioning, navigation and timing system, including the ground system and user equipment. 

According to the GAO, the Air Force examined nine alternatives for the GPS space segment, including continuing with the GPS 3 constellation under contract to Lockheed Martin Space Systems of Denver and scheduled to begin launching in 2015. The baseline GPS 3 program and slightly modified version were the highest-priced options, at $23 billion and $25 billion, respectively, but also came with the lowest technical and programmatic risk, the report said.

At the other end of the scale was a constellation consisting entirely of smaller satellites, called NavSats, that came with a $13 billion price tag but also was assigned the highest level of risk, the GAO study said. That option, along with a similar, $14 billion option that includes augmentation from geostationary orbiting satellites, would eliminate the nuclear detonation detectors carried today aboard GPS satellites, the GAO study said.

In between is a range of options that include launching satellites two at a time on a single rocket and constellations populated with various combinations of GPS 3 and NavSat spacecraft, the GAO study said. Some of these constellations would be augmented with payloads in geostationary orbits 36,000 kilometers above the equator — GPS satellites currently fly at about half that altitude. These augmentation payloads would fly aboard dedicated satellites or as hosted payloads aboard other government or commercial spacecraft, the GAO report said.

The dual-launch option for GPS 3 has been under consideration for more than two years; Lockheed Martin officials estimate it would save as much as $50 million per satellite. Rocket maker United Launch Alliance of Denver in June announced it would partner with space hardware maker Ruag Space of Zurich, Switzerland, to develop that capability for its Atlas 5 launcher, but Congress has yet to fund that activity. 

“Program officials indicated that this ongoing effort will require reductions in the size, weight, and power of the GPS 3 satellites, as well as development of equipment (adaptors) that will allow two satellites to fly on a single launch vehicle,” the GAO report said of the dual-launch option.

The small-satellite concept surfaced more recently. The Air Force late last year awarded contracts with a combined value of $3.8 billion to three companies — Boeing, ITT Exelis and Surrey Satellite Technology U.S. — to study low-cost satellites to augment the GPS constellation. Boeing Space and Intelligence Systems of El Segundo, Calif., has a history of building GPS satellites but lost to Lockheed Martin in the GPS 3 competition; Exelis Geospatial Systems of Rochester, N.Y., is the historical provider of U.S. GPS payloads; while Surrey’s parent company, based in England, is a leading small satellite maker and plays a key role in Europe’s Galileo satellite navigation system.

According to the GAO, the Air Force report may have understated the risks involved in developing the NavSats. “While the report acknowledges that there are technical risks involved with developing higher efficiency signal amplifiers and other space, weight, and power reducing technologies, it concludes that none of these technologies is high risk,” the GAO said. “However, officials from the Air Force Research Laboratory, which is helping to develop some of these technologies for potential application on NavSats, noted that some of the new technologies are currently at a relatively low level of maturity … and will not likely be feasible for the GPS program until at least 2018.”

Generally speaking, the GAO noted that the Air Force options were based on a notional constellation of 30 satellites, whereas the service’s minimum requirement for full GPS coverage is 24 satellites. Because there are significant cost differences between the two, the Air Force should clarify the number of satellites required in a future navigation constellation, the GAO said.

The Air Force should include the ground and user segments and actively engage civilian GPS stakeholders in future assessments of satellite navigation options, the GAO said.

The Defense Department concurred with these recommendations, the GAO said.

Warren Ferster is the Editor-in-Chief of SpaceNews and is responsible for all the news and editorial coverage in the weekly newspaper, the spacenews.com Web site and variety of specialty publications such as show dailies. He manages a staff of seven reporters...