Upper-atmosphere rotation rate determined from the orbit of China 6 rocket (1976-87B)

Abstract

The orbit of CHINA 6 rocket, 1976-87B, has been determined at 51 epochs during its 17-month life, using the RAE orbit refinement computer program, PROP 6, with over 4000 radar and optical observations from 49 stations. The orbital accuracy is about 100 m, radial and cross-track, on average. The rotation rate of the upper atmosphere, Λ rev/day, for the height-band 200–230 km, was calculated from the decrease in orbital inclination (after being cleared of perturbations) to give the following results: 1. (1) for morning conditions, Λ = 0.9 for May–June and August–September 1977, at 215km mean height; Λ = 0.7 for October–November 1977, at 210km; Λ = 0.8 ± 0.05 for January–February 1978, at 200 km; 2. (2) for evening conditions, Λ = 1.2 for July and September–October 1977, at 215 km; 3. (3) for mean (morning plus evening) conditions, Λ = 1.0 ± 0.1 between October 1976 and May 1977, at 230 km; Λ = 0.8 ± 0.1 for December 1977 to January 1978, at 215 km and mean latitude 57°S. Values of density scale height have been obtained from the variation in perigee height, including several values during the final 16 days to decay. Comparison with CIRA 1972 values shows agreement mostly within 10%.