Processing Optical Observation Data to Efficiently Verify Maneuver History and Orbital Tolerances of Geostationary and Geosynchronous Satellites

Abstract

Geostationary and geosynchronous satellites are meant to reside permanently at a desired longitude for reliable communications capabilities. However, they are sub- ject to numerous perturbations that cause movement in both the latitudinal and longitudinal directions over the course of their orbits, potentially eradicating their usefulness as ”stationary” or predictable communications objects. These perturba- tions include the gravitational force of the moon and sun, the triaxiality effect and solar radiation pressure. The extent of these effects on geostationary satellites has been determined empirically and mathematically to a level of accuracy that allows for predictions to be made about the amount of ∆v required for a satellite to perform orbital station-keeping and reside within desired tolerances in both the latitudinal and longitudinal directions, creating a ”Geostationary Orbital Budget Box” (GEO Box) in which the satellite can always be found. Using the equations governing these effects and measurements from optical observations of the TDRS 10 and TDRS 11 geosynchronous satellites, this paper outlines the engineering of a process that will verify the station-keeping maneuvers completed by these satellites by obtaining Right Ascension and Declination measurements and using orbital determination concepts. With this knowledge, the GEO Box of each of the satellites can be verified. This process is necessary for ensuring the proper operation of these satellites and is cur- rently expensive and inaccessible. This paper aims to approach this process in a novel and efficient way for use as a standard for more easily being able to verify desired tolerances for the lifetime of a geostationary satellite. It is not the creation of new theory, but the gathering and application of acquired knowledge to solve this verifica- tion problem that is the goal of this paper. The method produced is satisfactory for these goals and is able to be replicated using any orbital determination software in conjunction with known orbital mechanics equations. Maneuvers for both TDRS 10 and TDRS 11 were verified and confirmed using proprietary Python code for quickly iterating maneuver epochs and the ∆v required for those epochs.