quote:

---

From GatorGuy
A report today in GPS World highlights the dire straits facing the current GPS satellite system. As early as next year, the Air Force may no longer be able to maintain a constellation of 32 active satellites, with 8 in danger of imminent failure. A niminum of 24 must be maintained to assure sufficient positioning capabilities for ground based location. Some excerpts from the article follow:

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 . . ." 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."

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.

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.

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 . . . has been implementing both practices on an intermittent basis.

. . . 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.

The essence of the report is that if current satellites cannot be maintained until new ones are in place and operational, then civilian use may be restricted to a single band rather than the more precise positioning that Pres. Clinton allowed civilian access to a few years back. Military needs will get priority. And this may start ocurring as early as next year. Just thought you ought to know.

---