Global Positioning News

Tag: GAO

  • Out in Front: What’s in a Number?

    Computers killed a trusty companion of my teenage years. That is, after those proto-computers known as pocket calculators knocked him out and left him unconscious on the cooling floor.

    But I come to praise my slide rule, not to bury him.

    I marveled at the way he worked. You had a tactile relationship with numbers on a slide rule. You could see — and feel — how a small adjustment here effected a big change over there. With computers, it’s just numbers in, numbers out.

    Maybe that high-tech approach led both the GPS Wing and the Government Accountability Office into trouble with constellation gaps. GPS satellites have proven themselves very hardy in space, outlasting their predicted lifetimes. The GPS Wing has grown to lean on those longer lives a bit, and what with Congress and the Administration booting budgets a year or two to the right with addictive regularity, the Air Force has saved money by replenishing upon need. And need has been not all that great, so replenishment, and the contract awards and manufacturing that feed the replenishing line, have been allowed to relax.

    But not the mathematical models that someone has held to more conservative standards. Those models use the shorter predicted satellite lifetimes. When those models were projected against the real-world timelines for IIF and Block III — whoa GAO! Some black gaps suddenly yawned.

    Now we learn that GAO and the Wing will re-undertake this exercise, factoring instead the longer lifetimes that the satellites have proved capable of. Tinker a small adjustment here, see a big change out there.

    Speaking of numbers, I’ve grown fond of 20, and lately enamored of 200. The former being the number of years we have published this magazine, the latter the new world record for GNSS technical articles, attained by one Richard B. Langley.

    With characteristic Canadian unbravura, Langley fidgets and frets that we have made too much of him on this magazine’s cover and page 42. It looks too braggy for him and he feels uncomfortable with it. But I have prevailed upon him to swallow his humility, to take one for the team. We bask in his reflected glory.

    Quick, what’s the difference between 160 and 144.5? Not in absolute terms, but in tactical advantage. If I add a metric, east longitude, geosynchronous orbit, does that help? I’m puzzling out why Compass would move its G1 satellite from one location to another after only ten days in space. Better ground control might be the answer. But more mystifying, why China’s spokespersons at the Munich Summit would proffer the first location, when they must know very well — in fact, they so admitted when I confronted them with it — that the second is actually the case.

    Numbers don’t obfuscate. People do.

  • GPS Gaps Closing Up; West Coast Launches Aired

    Anthony Russo, director of the U.S. National Space-Based PNT Coordination Office, told the Munich Satellite Navigation Summit last month that, regarding the May 7, 2009, U.S. General Accountability Office report that forecast gaps in constellation availability, “The GAO will revise its report somewhat. They were using a model that was a little too cautious, one used by the [GPS] Wing. But satellites on orbit have been performing past estimated life. Further, we can turn off secondary payloads to conserve energy onboard satellites [and thus extend life] if needed.”

    GPS satellites have proven themselves very hardy in space, outlasting their predicted lifetimes. Relying on those longer lives, the Air Force has saved money by replenishing upon need. But the GAO report apparently used more conservative lifetimes for the mathematical models of constellation availability. When those models were projected against the real-world timelines for IIF and Block III, some gaps appeared. Now the GAO and the Wing will re-undertake this exercise, factoring instead the longer lifetimes that the satellites have proved capable of.

    In a hearing before the U.S. Senate Subcommittee on Strategic Forces, Committee on Armed Services on March 10, the following exchange occurred.

    Senator BEN NELSON.  “Ms. Chaplain, last year, the GAO issued a report that resulted in some significant and very negative press coverage about the health and reliability of the GPS system. Could you update us on the GAO’s assessment, now, of the GPS system?”

    Ms. CHAPLAIN (Director, Acquisition and Sourcing Management,
    from the Government Accountability Office (GAO)).
    “Yes. We’re currently conducting a review—a follow- on review. And the two programs we looked at, on the satellite side last year, were the IIF program and the IIIA program. And the IIF program has made some progress, and it’s getting ready for a launch fairly soon.

    “The IIIA program is on—it’s meeting its schedule currently. We still have concerns about the compressed nature of the schedule, and all the very difficult activities ahead for GPS IIIA, but it is not encountering any severe problems at this point.

    “When we look at the health of the Constellation, our findings are pretty similar to last year’s. One thing we weren’t discussing in last year’s report, that should probably brought out more when we talk about it this year, is some of the options the Air Force has available to it to manage GPS if they do have—experience some dips in the Constellation availability. There are options that they have to get through those periods.

    “Our concern is, you just—you don’t want to find yourself in a state where you’re looking at those kind of options; you want to make sure you do everything you can to keep the program healthy, resourced, and on track.”

    A recent story in Spaceflight Now attributes to Gary Payton, the undersecretary of the Air Force for space, a statement that the Air Force currently has under review an option  is to move some high-inclination flights, including future GPS satellite launches from Cape Canaveral to Vandenberg Air Force Base in California.

    “We would like to be able to get to the point where we can project six months or a year down the road that we’re going to have a surge of launches all ganged too close together, that we may pull a GPS launch over to Vandenberg,” the story quotes Payton as saying. “The same rocket and orbitology allows you to launch out of Vandenberg.”

  • GPS at Risk: Doomsday 2010

    The United States Government Accountability Office (GAO) issued on May 7 an alarming report on the future of GPS, characterizing ongoing modernization efforts as shaky. The agency appears to single out the IIF program as the weak link between current stability and ensured future capability, calling into doubt “whether the Air Force will be able to acquire new satellites in time to maintain current GPS service without interruption.” It asserts the very real possibility that “in 2010, as old satellites begin to fail, the overall GPS constellation will fall below the number of satellites required to provide the level of GPS service that the U.S. government commits to.”

    Prepared at the request of the U.S. House of Representatives’ Subcommittee on National Security and Foreign Affairs, Committee on Oversight and Government Reform, and titled “Global Positioning System: Significant Challenges in Sustaining and Upgrading Widely Used Capabilities,” the report concludes that “it is uncertain whether the Air Force will be able to acquire new satellites in time to maintain current GPS service without interruption. If not, some military operations and some civilian users could be adversely affected.”

    “In addition,” the report summary continues, “military users will experience a delay in utilizing new GPS capabilities, including improved resistance to jamming of GPS signals, because of poor synchronization of the acquisition and development of the satellites with the ground control and user equipment. Finally, there are challenges in ensuring civilian requirements for GPS can be met and that GPS is compatible with other new, potentially competing global space-based positioning, navigation, and timing systems.”

    Among the report’s principal recommendations is a proposal often made in past years by a range of experts, but never implemented: the Secretary of Defense should appoint “a single authority to oversee the development of GPS, including space, ground control, and user equipment assets, to ensure these assets are synchronized and well executed, and potential disruptions are minimized.”

    While the Department of Defense (DoD) concurred with this recommendation, and while quite possibly it might effectuate the streamlined decision-making and corollary processes to remedy the highlighted deficiencies, it would run counter to the integral “dual-use” principle of GPS as dedicated to both civil and military users. Such a move could thus conceivably and adversely affect the interests of civil users.

    The full report can be downloaded from the GAO website.

    Testimony from invited GPS providers and users before a related National Security Subcommittee hearing (“GPS: Can We Avoid a Gap in Service?”), some of which is briefly encapsulated within this news story, can be downloaded.

    Why GAO Did This Study. A highlights document attached to the GAO report asserts that GPS “has become essential to U.S. national security.” The GAO conducted its own analysis of Air Force satellite data, in addition to interviewing key officials and analyzing program documentation. Specifically, the agency assessed progress in:

    • acquiring GPS satellites
    • acquiring the ground control and user equipment necessary to leverage GPS satellite capabilities
    • coordinating efforts among federal agencies and other organizations to ensure GPS missions can be accomplished.

    Gloomy Outcomes. Based on the most recent satellite reliability and launch schedule data from March of this year, the estimated long-term probability of maintaining a constellation of at least 24 operational satellites falls below 95 percent during fiscal year 2010 and remains below 95 percent until the end of fiscal year 2014, at times falling to about 80 percent. Program officials provided no evidence to suggest that the current mean life expectancy for satellites is overly conservative, the GAO stated.

    The results of fewer than 24 operational satellites could include:

    • Intercontinental commercial air carriers may have to delay, cancel, or reroute flights.
    • Enhanced-911 response to emergency calls could lose accuracy, particularly operating in urban and mountainous environments — exactly where emergencies tend to be most dire and hardest to locate.
    • Accuracy of precision-guided munitions could decrease, forcing the military to use larger munitions or use more munitions on the same target to achieve the same level of mission success, and increasing the risks of collateral damage. The urgent desire to decrease or eliminate collateral damage to civilians in or near conflict zones has often been cited by the founders of GPS as one of their key motivations in envisioning the program.
    • Both standard positioning service and precise positioning service could suffer, impacting large numbers of civil users, both professional (for example, surveyors) and casual (users of location-based services via cell phones) in moderately mountainous areas, in large cities, and under forest foliage.

    Block IIF at the Crux. Cristina T. Chaplain of the GAO presented the report to Congress, stating, “In recent years, the Air Force has struggled to successfully build GPS satellites within cost and schedule goals; it encountered significant technical problems that still threaten its delivery schedule; and it struggled with a different contractor. As a result, the current IIF satellite program has overrun its original cost estimate by about $870 million and the launch of its first satellite has been delayed to November 2009 — almost three years late.”

    The GAO reports cites specific problems with the IIF satellites contracted to Boeing. During the first phase of thermal vacuum testing in 2008, one of the test payload’s transmitters failed; consequently, the program suspended testing in August 2008 to identify the causes and take corrective action. Other hang-ups include maintaining the proper propellant fuel-line temperature, delaying final integration testing, and re-design of the satellite’s reaction wheels, used for pointing accuracy, because of on-orbit failures on similar reaction wheels on other satellite programs. Overall, about $10 million additional have accrued to program, according to the GAO.

    “Further, while the Air Force is structuring the new GPS IIIA program to prevent mistakes made on the IIF program, the Air Force is aiming to deploy the next generation of GPS satellites three years faster than the IIF satellites. GAO’s analysis found that this schedule is optimistic, given the program’s late start, past trends in space acquisitions, and challenges facing the new contractor.

    “Of particular concern is leadership for GPS acquisition, as GAO and other studies have found the lack of a single point of authority for space programs and frequent turnover in program managers have hampered requirements setting, funding stability, and resource allocation.

    “If the Air Force does not meet its schedule goals for development of GPS IIIA satellites, there will be an increased likelihood that in 2010, as old satellites begin to fail, the overall GPS constellation will fall below the number of satellites required to provide the level of GPS service that the U.S. government commits to. Such a gap in capability could have wide-ranging impacts on all GPS users, though there are measures the Air Force and others can take to plan for and minimize these impacts.

    “In addition to risks facing the acquisition of new GPS satellites, the Air Force has not been fully successful in synchronizing the acquisition and development of the next generation of GPS satellites with the ground control and user equipment, thereby delaying the ability of military users to fully utilize new GPS satellite capabilities.

    “Diffuse leadership has been a contributing factor, given that there is no single authority responsible for synchronizing all procurements and fielding related to GPS, and funding has been diverted from ground programs to pay for problems in the space segment. DoD and others involved in ensuring GPS can serve communities beyond the military have taken prudent steps to manage requirements and coordinate among the many organizations involved with GPS. However, GAO identified challenges in the areas of ensuring civilian requirements can be met and ensuring GPS compatibility with other new, potentially competing global space-based positioning, navigation, and timing systems.”

    Staving Off Disaster. In the course of its interviews with key officials, the GAO learned of and reports on some alternatives that have been examined. The Air Force Scientific Advisory Board considered the use of smaller GPS satellites in 2007. These could be developed more quickly and at lower cost. The board concluded that while small satellites could at some point serve to augment GPS capabilities, they would require a different and much more extensive ground control segment, program development would take too long, and necessary changes to user equipment would render the whole scheme cumbersome.

    The effects of satellite power loss over time, due to harsh space conditions, could be mitigated by shutting down satellite subsystems when not needed, reducing power consumption, also by shutting off a secondary (unnamed) GPS payload. DoD has long been reluctant to take either measure absolutely, particularly the second one, but according to testimony (see below) has been implementing both practices on an intermittent basis.

    Day in Congress. Other GPS community representatives testified to the House Oversight and Government Reform’s subcommittee on National Security and Foreign Affairs, alongside GAO spokesperson Chaplain.

    According to Lt. Gen. Larry D. James, Commander, 14th Air Force, Air Force Space Command, and Commander, Joint Functional Component Command for Space, U.S. Strategic Command, the Space Command maintains the required minimum of at least 24 GPS satellites in orbit, and the current level of 30 operational satellites, by keeping a “ghost fleet” of older, partially mission-capable satellites in backup mode. “Currently, three vehicles are held in residual status and are returned to the constellation every six months to ensure operational capability.” He stated that added life also is being squeezed from the satellites by reducing power to or turning off equipment for secondary missions aboard the satellites.

    Karen Van Dyke, acting director for Positioning, Navigation and Timing in the U.S. Department of Transportation’s Research and Innovative Technology Administration (RITA), told the Congressional committee that “GPS is vulnerable to interference that can be reduced, but not eliminated.” Citing the 2001 Volpe Report for which she was a key author, she stated that there has long been “an awareness within the transportation community of risks associated with use of GPS as a primary means for position determination and precision timing. Due to the reliance of transportation on GPS signals, it is essential that threats be mitigated and alternative back-ups be available, and the system be hardened for critical applications. DOT has determined that sufficient alternative navigation aids currently exist in the event of a loss of GPS-based services.”

    Nearly simultaneously with the GAO report and congressional hearings, the long-withheld Independent Assessment Team report on eLoran as a GPS backup has just been released.

    F. Michael Swiek, Executive Director, U.S. GPS Industry Council and a member of GPS World’s Editorial Advisory Board, reminded Congress of the dual-use nature of the system, saying “The U.S. Government has promoted and encouraged [GPS] development by establishing, maintaining and reinforcing a stable policy framework that has consistently received farsighted and bipartisan support. It has been a true partnership of shared visions, discussions and debates, cooperation, and coordination. This has been possible through the open dialogue that has taken place since the early days of GPS, some 25-plus years ago, between civilian and military, industry, and government on technical and policy issues as the technology, system, and applications have evolved.”

    Swiek made his recommendation that “successful adoption of modernized civilian GPS signals will occur if the installed user base can continue to trust the consistent and stable policy framework that the U.S. government has provided for GPS for two decades. The new signals will need to sustain the legacy of accuracy, availability, and reliability established over the past 20 years.”

    Chet Huber, president of OnStar, a wholly owned subsidiary of General Motors Corporation, and at nearly 6 million active subscribers probably the largest single group of civil GPS users, offered three recommendations:

    “First, we must address the health of the current constellation. We are concerned that a recent report shows eight of the current satellites are one component from total failure. Loss of signal will likely immediately affect GPS accuracy and availability (geographic coverage).

    “Second, as the GPS system is modernized, it is imperative that the U.S. government formally commit to preserving the L1C/A signal and to ensuring backward compatibility for legacy applications with no loss of performance from current levels.  . . . Any modernization initiative that degrades backward compatible performance — such as reducing the number of satellites making up the constellation — would likely adversely impact the provision of services by OnStar, including the quality of location information we provide to public safety, thereby potentially increasing the response time of public safety personnel to crash victims and others in need of emergency services.

    “Our third recommendation — and this is also important to legacy applications — is that we commit to maintaining the current PRN code (or satellite signature structure) for the primary orbital slots, as satellites in those slots are replaced. Legacy hardware is not capable of being expanded to accommodate more than 32 slots so renumbering above 32 will likely affect performance of legacy applications.”