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An Examination of Coarse Sun Sensor Contingencies in Attitude Determination and the Sun Vector CalculationSatellite pointing is vital to the success of a mission. One element of that entails describing the position of the sun relative to the frame of the satellite. Coarse Sun Sensors (CSS) are typically used to provide the information to calculate the sun's position in Safe Modes or contingency operations. In the OCO-2 configuration there are 13 CSS total, which provide redundant 4 celestial coverage. Failures of the individual CSS elements can introduce holes in the celestial coverage resulting in potential loss of sun knowledge. These failures must be analyzed to determine if the contingency plan is sufficient to assure mission success. First the static case was looked at and determined that at a maximum, 3 CSS failures can be sustained on the body and 1 on the array without causing coverage holes. Also array sensors are more important to mission success. The Sun Vector calculation has been transcribed to MATLAB code and failure scenarios are being examined to determine the maximum error given a set of failure scenarios. This activity indicated that if there is a loss of the sun, the sun-searching algorithm could be modified to use XZ rotation as that is guaranteed to find it whereas the design using the YZ rotation misses the sun if it is at the + or - Y orientation.
Document ID
20150005602
Acquisition Source
Jet Propulsion Laboratory
Document Type
Other
External Source(s)
Authors
Coffey, Brenman
(Jet Propulsion Lab., California Inst. of Tech. Pasadena, CA, United States)
Welch, Ray
(Jet Propulsion Lab., California Inst. of Tech. Pasadena, CA, United States)
Burt, Brad
(Jet Propulsion Lab., California Inst. of Tech. Pasadena, CA, United States)
Date Acquired
April 13, 2015
Publication Date
August 1, 2012
Subject Category
Solar Physics
Distribution Limits
Public
Copyright
Other
Keywords
celestial bodies
Coarse Sun Sensors (CSS)
attitude control system (ACS)

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