A few short weeks ago, the U.S. GPS program had its posterior firmly planted in the catbird seat. Government spokespeople in international fora looked on benignly as European, Chinese, and Russian GNSS programs struggled to resolve their issues and meet their heady challenges. All was well with the world. A new GPS satellite launched, a segment of radio-frequency spectrum secured for a promising new signal, a next-gen satellite shipped to the Cape, and the next-next-gen program nearing successful preliminary design review (since completed).
In the blink of an eye, the world is turning.
A progression of seemingly unrelated events began to affect GPS outlook.
- While successfully broadcasting the new L5 signal, IIR-M (20) also began generating “out of family” measurements on L1 and L2 at low elevations.
- The long-withheld Independent Assessment Team (IAT) report on eLoran appeared, unanimously recommending that “the U.S. government complete the eLoran upgrade and commit to eLoran as the national backup to GPS for 20 years.” While in itself this is good news — that is, if you believe in backing up critical systems — it does not augur well that a two-year Freedom of Information Act fight had to be waged to pry the report loose from know-nothings in the Department of Homeland Security, and that the vaunted Obama administration, heralded as a breath of change, had earlier come down on the same-old same-old government side of taking Loran out.
- Then, the motherlode. The U.S. Government Accountability Office (GAO) issued a report on the future of GPS, characterizing the constellation as susceptible to falling below full operational capability between 2010 and 2018.
- It turns out that while a IIF payload did travel to Cape Canaveral on May 7, this was solely for the purpose of preliminary launch-system compatibility testing. The satellite itself is not ready to operate in space, and in fact the IIF currently at the Cape is just a placeholder. Or, to use press-release verbiage, to “serve as a risk-reduction pathfinder for SV1 processing later this year.” The real satellite, the IIF that may, repeat may, go into orbit at the end of this year or early next year, continues in critical payload testing at the contractor facility.
- Here’s a bright spot, at long last. Brad Parkinson, the first GPS Program Office Director, chief architect and advocate for GPS, has a plan for mitigating possible GPS brownouts — the gaps in service that may occur if the constellation should fall below quorum. Parkinson states that “It is possible that the constellation will be at a level of less than 24 satellites. I would like to focus on the options that would help reduce this risk.”
Parkinson cites two principal causes for the current at-risk status of GPS service. “The first is that the generation of replacement satellites called IIF has been greatly delayed. A substantial part of the reason for this is that the contract for IIF satellites was placed during a period when DOD imposed a grand experiment in contracting. In addition there were some changes to the satellite to modernize its design, but the bottom line is the satellite has been on contract since 1996 and will not be launched until 2010. The design is quite old, and the capability of the satellites does not meet the latest requirements.”
The second cause is protracted delays by the decision-making and budgeting processes in getting Block IIIA going. These issues have now been resolved, and Parkinson points out that both reasons “are now a matter of history. The current issue, that should concern us all, is: what options should we pursue to substantially reduce the risks of brownout.”
Parkinson makes three recommendations in his personal presentation to the PNT Advisory Board meeting; the same presentation was also submitted as written testimony to the Congressional hearing following on the GAO report. Download the full Powerpoint file, with written details.
“In my view, there are three major options for mitigating brownouts. Fortunately, these options could be done together. These are:
- To reactivate the previously retired GPS satellites that are still operating in normal GPS orbits.
- To speed up the GPS IIIA development space (expedite the milestone approvals).
- To develop a simplified GPS IIIA based design, Spartan satellite (IIIS) that would not include the extra payloads, and, once designed, could be built quickly and launched into space with two satellites on a booster. This would be done in parallel with the current program.”
Dr. Parkinson adds that “There is a fourth option, which may have been offered by some. This is to restart or expand the GPS IIF production line. The apparent advantage of this is that the GPS IIF is close to its first launch. Some might think major advantage would have been the fact that it is already designed. Weighing against this advantage is the fact that the design and the parts are obsolete. Virtually all the boxes and components would have to undergo a major redesign. Furthermore, the design is still untried, and was developed during an era of flawed procurements.”
Counterpoint. Boeing says its engineers are working “very closely with the Air force and its team” and that the company has taken “aggressive steps to resolve the technical issues on IIF with a strong emphasis on mission assurance.” It maintains that it is on track to deliver the first IIF satellite, ready for launch, later this year.
“Boeing’s GPS IIF satellites,” the press release continues, “will deliver more capability and improved mission performance to military and civilian users. . . . Design changes were required to ensure performance over the satellite design life and these have caused schedule delays, but these changes are in the final phase of implementation and a fully integrated satellite (SV1) has already successfully completed the thermal-vacuum test program — the most stressing system level test. SV2 was shipped to the Cape (Canaveral) on May 6 to perform system-level compatibility tests and serve as a risk reduction pathfinder for SV1 processing later this year.”
The Department of Defense also made a presentation to the May 14–15 National Space-Based PNT Advisory Board meeting, and in it highlighted three risks: delay of IIF, delay of the ground control segment (OCX) contract award, and delay of GPS IIIA.
Some in the GNSS community feel that the GAO-generated furor focuses too much on Block IIF and not enough on these other unknowns. They foresee a strong likelihood that the IIF satellites will get aloft on time, suitably “following on,” as they have been named. The real scary part will come later, in the 2015-2017 timeframe when GPS IIIA doesn’t get into orbit in sufficiently quick
Further, the GAO report did not account for two mitigation tools that the DoD has in reserve: three retired satellites still in space that could be brought back into operation, and power-shedding as a means to extend satellite life.
Back to the Mitigation Talk.Coming up are some of the strongest words Parkinson employed in the PNT Advisory Board presentation: further congenital defects.
“While the Air Force has undertaken a very rigorous test program,” read the presentation notes, “it is still conceivable that we will find further congenital defects. The IIF satellite lacks the powerful military signal that will be extremely helpful against potential hostile jammers. In addition, it does not broadcast the new international signal L1C. Because of the extensive redesign it seems probable that the satellite would have to be re-competed. Finally, this would be a major near-term budget hit in a period when the IIF satellite is still over running its budget.”
Not Even Half the Picture. GPS program planners have one of the most complex tasks going. They must consider many other issues in addition to keeping an integer number of satellites flying. Dual handling of the space and ground segments while both undergo modernization so that they remain in phase with each other, further synchronization with military user equipment on its own track of development, operating under a leadership and decision-making structure that lacks unity at the top, structuring future interoperability with other GNSS neither aloft nor complete in their signal-structure design — and then the various PR issues involved with servicing a worldwide, multinational, multi-industry, multi-requirement customer base.
Personally, I feel much more comfortable here in my armchair.
And despite all the grim news this month, I remain confident that GPS will continue to lead the field of GNSS, providing exemplary service round the clock, round the world.