Abstract

Accurate orbits of the high-drag satellite 1968-59A, which had an initial perigee height of 160 km, have been obtained at 9 epochs during its 117-day life with the aid of the R.A.E. orbit determination program PROP. All available optical and radar observations were used. On most of the orbits the perigee height has a standard deviation less than 0.4 km; for the longitude of the node and the inclination i, the average s.d. is 0·003°. The value of i decreased from 89·88° initially to 89·75° just before decay, mainly due to the effect of atmospheric rotation, and by fitting a theoretical curve the following values were obtained for the atmospheric rotational speed, expressed as times the Earth's rotational speed: = 1·20 ± 0·07 at 170 km height; = 1·1 ± 0·1 at 150 km.