Passive Accelerometer System (PAS) - MGBX

PAS Experiment PAS Experiment PAS Experiment


The objective of the passive accelerometer system (PAS) is to measure, at various locations in the spacecraft, the small (10-6 mg) quasi-steady residual acceleration caused by a combination of atmospheric drag effects and the gravity gradient.

Shuttle-Mir Missions

PAS was deployed on 10 separate occasions between October 20 and December 17, 1996. The acceleration measurement is obtained by recording the motion of a spherical proof mass along an oriented liquid-filled tube. Modified Stokes' Law uses trajectory and speed to calculate acceleration.

Successful operation. Measured accelerations up to 1.9 mg and as low as 5 X 10-2 mg. High and low accelerations measured at the same location but at different times.

Higher acceleration values consistent with orbital attitude and estimated atmospheric drag. Lower values suprising. Explanation: simulations show that proximity to CG + quasi-inertial attitude can lead to periods of practically no proof mass motion when the drag accelerations are low enough (low average acceleration).

J. Iwan D. Alexander and M.J. B. Rogers, Passive Accelerometer Measurements on Mir and STS-50, to be submitted to Microgravity Science and Technology, 1999.

Principal Investigators
J. Iwan D. Alexander
Case Western Reserve University

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Page last updated: 07/16/1999