REVIEW OF AIR DENSITY MODELS FOR ORBIT DETERMINATION

This paper discusses an assessment of some of the thermospheric models considered during Indian Remote Sensing Satellite (IRS) Orbit Determi nation analysis. The impetus of such study is originated to choose an accurate and appropriate density model for precise orbit determination , orbit keeping and scene referencing. The accurate prediction of the motion of a near-Earth artificial satellite is primarily dependent upo n two factors, one is how well the initial conditions can be estimated and the other is how well the dynamics are understood, modeled and in tegrated. It is also a well-known fact that atmospheric drag is one of the major contributors of uncertainty in prediction of the motion of the near-Earth satellite. In this paper basic thermospheric properties are explained. Comparisons of preselected density models, along with results, are presented. Orbit determination analysis to choose an accu rate density model along with impact of solar activity on ground track control are briefly described. The MSIS-86 density model is chosen as being the best compromise between accuracy, flexibility and computati onal aspects.