Microvibration effects on a line of sight attitude stability appear to become a significant constraint for several future missions. The overall performance is highly sensitive to the amplification factor brought by the structural distortions. Orbit microvibration tests on a SPOT 1 satellite were performed in order to characterize the structural damping factor of a spacecraft's major eigenmodes in orbital conditions under a very low dynamic environment. The experiment principle consists in the comparison of two images of the same area taken in the same conditions: same instrument, same aspect angle, same position on orbit. The first image is used as a reference, while the second one is disturbed by a calibrated dynamics disturbance. SPOT 1 images are a very good microvibration sensor since they are sampled at a 600 Hz frequency. Special attention was put on the geographic areas selection for the images which allowed to decrease the correlation noise to a very low level. The dynamic disturbance was generated by a random sequence of torque commands on a reaction wheel, while the AOCS (Attitude and Orbit Control System) control was inhibited. Thus, the disturbance signal had a large spectrum range where the NASTRAN analyses of SPOT 1 on orbit behavior had computed the major spacecraft eigenmodes. The spectrum of disturbance on the images compared to NASTRAN prediction allowed a good damping factor order of magnitude characterization.
In Orbit Microvibration Tests on SPOT-1 Satellite Experiment Principle and Results
1991
4 pages
Report
Keine Angabe
Englisch
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