MACPROP: A Revised Program for the Refinement of Satellite Orbital Parameters

Abstract

Computer programs for the refinement of the orbital parameters of an artificial Earth satellite have been in use since 1957. One of the programs in current use is PROP. This program takes an initial estimate of the orbital parameters of an Earth satellite, together with observations of the satellite, and refines the parameters by a least squares differential correction process. The current version of PROP, known as PROP6, has been investigated and a new version, MACPROP, written. A description of the refinement process is presented, together with a detailed investigation of each segment of the program. Changes to the program have been made to remove some programming errors. Additional facilities have been written into the program so that the user has greater control over some of the physical quantities used by the program. Further changes have been made to make PROP easier to use. Each change has been described and details of the use of the additional facilities are given. MACPROP has been tested, using some of the new facilities, and the results are compared with those obtained by using PROP6. MACPROP is found to be slightly smaller and much faster than PROP6. The performance of PROP is improved by using MACPROP, particularly if some of the physical quantities used within PROP are varied. The orbital parameters obtained from MACPROP differ slightly from those obtained from PROP6 and may be accepted by the user with greater confidence, in the light of this investigation.