ADVANCED ORBIT/EPHEMERIS SUBSYSTEM (AOES) TIME TRANSFORMATION REVIEW
AEROSPACE CORP EL SEGUNDO CA SYSTEMS ENGINEERING OPERATIONS
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The space-time reference frame most convenient for the calculations of satellite ephemerides is not, because of the earths motion, the most convenient reference frame in which satellite positions may be measured by an observer on the earth. Integration of the equations of motion describing the satellite motion is most conveniently carried out in an inertial coordinate system, while observation is most conveniently carried out in a coordinate system fixed with respect to the surface of the earth. Transformation from the inertial to the earth fixed systems and vice-versa is a straightforward, though often tedious, computational exercise. This transformation requires a knowledge of the earths motion with accuracy commensurate with the accuracy required from the transformation. The present report concentrates attention on the coordinate systems and transformation schemes employed by the Advanced OrbitEphemeris Subsystem AOES computer programs presently being implemented by the Air Force Satellite Control Facility. The relations between the time scales employed by it and the computation of time dependent inputs to the spatial transformation procedures of AOES are reviewed. The basic equations are presented and the numerical constants appearing in the programs are evaluated.
- Celestial Mechanics
- Spacecraft Trajectories and Reentry