Analysis and application of frozen orbits for the TOPEX mission

This paper identifies and analyzes frozen orbits for use by the Topography Experiment (TOPEX) mission. Frozen orbits are characterized by almost no long-term change in eccentricity or argument of periapsis. The standard method of frozen orbit prediction is shown to be inadequate for TOPEX inclinations due to the effect of higher degree zonal harmonic gravity terms. A method is described from which long-term motion in mean eccentricity, argument of periapsis, and inclination can be predicted without numerical integration and is used to locate frozen orbits. A zonal gravity field of degree 13 is shown to be necessary and sufficient for TOPEX frozen orbit prediction. Results are verified by numerical integration methods. Frozen orbits are available for most TOPEX orbits under consideration and short-term altitude variations and maximum altitude rates are specified. Alternatives to the frozen orbit which may result in lower altitude variations and rates are briefly examined.