Unexpected but necessary adjustments to a satelliteborne test of relativity theory have consumed more than a quarter of the 13-month period the mission had allotted to collecting data. On Aug. 27, the Gravity Probe B (GP-B) experiment, which was launched into Earth orbit on April 20, finally began what's now expected to be a 10-month run of gravity measurements.
Despite the anticipated shortfall of data, the experiment should achieve the measurement precision originally expected, says Bob Kahn, a mission spokesman. As a consequence of the delay, however, observations of a reference star won't be as thorough and so won't give scientists as much backup data as planned.
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