Analysis of the orbit of the satellite Cosmos 482 in its last 15 days

Abstract

The satellite Cosmos 482 (1972-23A) was launched on 31 March 1972 into an orbit of eccentricity 0.42 inclined at 52° to the equator, and decayed on 5 May 1981. Orbits have been determined daily in the last 15 days of its life from NORAD and U. S. Navy observations, with the aid of the R. A. E. orbit determination program PROP 6. The orbital accuracy was about 40 m radially and cross-track. Various properties of the upper atmosphere were determined by analysing four of the orbital elements. The decrease in orbital inclination gave two values for atmospheric rotation rate at heights near 200 km, a morning value of 0.90 ± 0.05 rev/day and an average value of 1.05 ± 0.10 rev/day. The variation in the right ascension of the node, after removal of perturbations due to gravity and atmospheric rotation, gave a value for the meridional wind at a similar height: the wind was weak, 20 ± 20 m/s north to south at 08 h local time. From the decrease in perigee distance, density scale heights were determined at heights of 180-220 km accurate to 3%, and were found to be significantly higher (by 6%) than those indicated by the COSPAR International Reference Atomsphere; at the high levels of solar activity prevailing in 1981, CIRA gives too low a scale height. Finally, the angular motion of perigee was analysed, and indicated a day-to-night variation in density 0.7 ± 0.1 of that given by CIRA , implying a value of 1.14 ± 0.02 for the ratio of maximum day-time to minimum night-time density at 180 km height in April-May 1981.