DOD Seeks Options for Forging Ahead on GPS III
With the continuing strains on the U.S. national budget and the possibility that the Administration’s sequestration program could last for several more years, Pentagon planners are said to be worrying that the costs of the future GPS III system could become out of reach, despite its major advances and the need to have modernized replacement satellites ready to be deployed as the orbital lives of current satellites end.
But to simply replace current satellites with more of the same would be a backward step for the Department of Defense and, to a lesser extent, the civil user community. The DOD’s needs are fundamental, because the system’s primary purpose is, and always has been, defense. (However, the number of civil users around the world, who today enjoy its benefits at no cost–including even those who appear to be our adversaries–vastly exceeds the number of systems employed by DOD and its overseas allies.) And from the beginning, the U.S. has committed to the world that the GPS civil service will always remain free to all users.
So the money crunch comes with the increased impact of the next-generation GPS III system, where the cost of each of its satellites is already forecast, several years before their first production and launch, to be nearing half a billion dollars. Compounding that, experience in the mountainous areas of Afghanistan and elsewhere, where signals can be blocked by high terrain, now shows that the normal 24-satellite constellation is no longer adequate for full-time worldwide military signal availability, and even the current 30-satellite configuration is marginal, should one or two in-orbit failures occur, raising the possibility of a future 33-satellite system, with some in non-circular orbits. But DOD officials are said to consider such costs to be beyond the department’s budget.
Consequently, DOD and industry engineers are seeking ways to reduce costs, and a number of intriguing proposals are now being investigated. The military electronics payload, most of which is classified, accounts for just over half of each satellite’s cost. At least two of these costly systems have been identified. Nudets–a nuclear detonation and explosion tracking system that instantly pinpoints nuclear explosions anywhere on earth and relays that information down to listening earth stations–is said to be by far the highest-cost element, while nuclear “hardening,” to shield the satellites’ electronics from nearby nuclear weapon blasts, is also reportedly costly. But neither is likely to be removed from future satellites, although newer technology may reduce their size, weight and (probably marginally) cost.
The DOD is also planning to extend the acceptable orbital lives of its current satellites, sources have told AIN. The satellites carry a number of triple-redundant systems, and when two of those triple systems fail, the satellite has been removed to a parking orbit and a fully serviceable replacement launched. The new approach will be to leave the partially failed, but still operating, satellite in the constellation, to be replaced with another from the parking orbit when it finally fails. This technique works, and does provide a quicker replacement and save money. In one recent case, a satellite down to its final thread continued to operate satisfactorily until it reached its 19th year in orbit, compared with the normal 10 to 12 years. That sounds commendable, until one considers that its 2013 operation depended on 1993-vintage technology and software, which would appear to lessen the attractiveness of the scheme.
What other options are there? Brad Parkinson, now a university professor but formerly a USAF colonel who led the original GPS concept development team, has proposed the development of “NibbleSats” that would carry only the basic GPS signal transmissions and could potentially replace roughly half of the constellation’s full military/civil space vehicles. “Nibble” suggests the process of “nibbling away” at the heavy and costly military–and possibly some civil–elements to end up with a less expensive satellite that retains all the essential GPS navigation capabilities. This would also have a valuable domino effect, in reducing the NibbleSat’s size, weight, power requirements, solar panels and heat dissipation needs. In turn, the size reduction would allow two, and maybe as many as four, NibbleSats to be launched into orbit on one booster rocket, compared to the single heavy mission booster required to place a “full” GPS military/civil satellite into orbit. Parkinson proposed that the NibbleSats would alternate one for one with the full satellites around the three GPS orbits. Apparently he has also shown that halving the number of Nudet satellites in the constellation, and spacing them appropriately, would not diminish their detection capabilities.
AIN understands that, possibly in view of the absence of any better alternatives, the concept has received fairly wide support from military and industry sources, with the major concern being whether, if and when approved through myriad federal service and bureaucratic levels, NibbleSat prototypes can be designed, built and their interfaces with full satellites tested for space-flight and then installed in the first three of the GPS III satellites before their expected launch in 2016. It will be a tight schedule that DOD is said to be reluctant to delay.