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Attitude stability of LDEF: Refinement of results from the silver pinhole cameraA measurement was previously described of the angular offset and attitude stability of the LDEF spacecraft using a simple pinhole camera device in the UAH experiment A0114. This device uses a silver surface to record the impact zone of atmospheric atomic oxygen passing through a small pinhole on the front surface of the satellite. The shape and size of this zone are well defined if the satellite velocity and gas temperature are known. The circular symmetry of the zone would be distorted by oscillation of the LDEF about its stable attitude, or by the effect of the co-rotation of the Earth's atmosphere for cases of satellites in nonequatorial orbits. The observed ellipticity of 1.05 with the major axis in the yaw direction is equivalent to an oscillation of + or - 0.2 deg about the stable attitude. The uncertainty in that measurement was estimated at about 0.1 deg. A refined analysis based on summing distributions of flux versus incidence angle for a large number of orbital positions, and including a co-rotating atmosphere, indicates that the combined distributions produce a result consistent with the measured exposed spot. It is suggested that, within the precision of the measurements, no actual oscillation of the LDEF is required to produce the results. Thus, the LDEF may have maintained a stable attitude to better than 0.1 deg, even under conditions of maximum aerodynamic perturbation when the silver oxygen record was made. This error is some two orders of magnitude lower than the predicted uncertainty in yaw oscillation and may indicate that the predict methodologies are too conservative.
Document ID
19920017976
Acquisition Source
Legacy CDMS
Document Type
Conference Paper
Authors
Peters, P. N.
(NASA Marshall Space Flight Center Huntsville, AL, United States)
Gregory, J. C.
(Alabama Univ. Huntsville., United States)
Date Acquired
September 6, 2013
Publication Date
June 1, 1992
Publication Information
Publication: NASA. Langley Research Center, Second LDEF Post-Retrieval Symposium Abstracts
Subject Category
Spacecraft Design, Testing And Performance
Accession Number
92N27219
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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