Orbital decay of Rohini /RS-1/ satellite

A comparison of the predicted and observed orbital decay of the recently launched Rohini satellite using the SLV-3 rocket in its E-02 flight is presented, highlighting the adequacy of some of the modelling aspects. The decay prediction involves an analytical method, the general perturbation technique, which treats the atmosphere as an oblate with the same ellipticity as the earth and rotating in a west-to-east direction. The ratio of the angular velocity of the atmosphere to that of the earth is assumed to be 1.2. Satellite orbital parameters and their estimated standard deviations as computed from observed Doppler data are shown. The deviations at the end of 200 days in semimajor axis and eccentricity are of the order of 30 kms and 0.0035, respectively. To assess the impact on lifetime estimation, parameters for ten previously launched satellites are considered. The predicted and observed lifetimes agree fairly well.