Gravity Probe B

is emphasizing small, inexpensive science missions, Gravity Probe B remains one of the most costly space physics missions that has ever been undertaken.

In any case, the proposed test of relativity, critics argue, simply is too complex for its results to be believable and the probe's tolerances too unforgiving to perform as promised in the rigors of space.

The project's survival hung in the balance most recently last year, when NASA suspended $50 million in project funding while a panel of a dozen academics from the National Academy of Sciences led by Princeton Nobel laureate Val Fitch aired misgivings about the project's scientific merits.

When a majority of the scientists on the panel concluded that "GPB is well worth its remaining cost to completion," NASA restored the project's funding. Agency officials allocated $75 million in August to keep the project moving toward its launch date.

Despite its endorsement, the panel still had many reservations about the sheer complexity of the endeavor Stanford was undertaking. "Nevertheless, the extraordinary experimental requirements and the impossibility of ground tests of some critical systems at the necessary level of accuracy introduce significant risks," the panel warned.

"A majority of the task group believes that GPB has a reasonably high probability of achieving its design goals and completing the planned measurements. However, based on their experience with complex experiments on the ground, several members remain skeptical.

"The task group notes in any event, should the GPB experiment be completed successfully but yield results different from those predicted by general relativity, the scientific world would almost certainly not be prepared to accept them until confirmed by a repeat mission."

The questions that dog Gravity Probe B in some instances go beyond issues of technical competence to reflect the deep faith the scientific community at large has invested in Einstein himself. An internal NASA memorandum that

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