May 1982:letters

Recovery Times of Cosmos Modules

Sir, After about a month into their respective flights, it was reported that Cosmos 929 and Cosmos 1267 had separated large modules (possibly large enough to be manned on future missions) which were recovered on Soviet soil. Although recovery dates have been quoted, the times of the recoveries have not been listed.

The two flights were in orbits inclined at 51.6 degrees and were in the same general altitude range as the manned Soyuz craft. Therefore, it is possible to estimate the landing times of the modules from a comparison with the Soyuz recoveries. Past experience shows that from 1979 to date, manned recov¬ eries have been made on tfie orbit which crosses the equator passing northbound between longitudes 11 degrees E and 20 degrees E.

When Cosmos 929 was operating, however, the Soyuz craft were being recovered one orbit later than this, and if Cosmos 929 followed these early flights, 89 minutes should be added to the times quoted below for that mission to give the corre¬ sponding times for the next orbit. The recovery of the Cosmos 929 module is thought to have taken place between 16-18 August 1977: a consideration of the times of passing over the nominal landing site, and also that the recovery took place before the manoeuvre to the 90.8 minute orbit, rules out 18 August. On 16 August Cosmos 929 crossed the equator northbound at 19.19 GMT (all times here are GMT) over 18.3 degrees E. This suggests a recovery at 19.54 for the object whith would already have separated from the Cosmos. On 17 August the corresponding crossing was at 18.56 over 17.7 degrees E. This implies a recovery at 19.31.

Turning to Cosmos 1267, the recovery seems to have been on 24 May 1981, approximately mid-way between the recoveries of Soyuz 40 and Soyuz T-4. On 24 May Cosmos 1267 crossed the equator at 20 degrees E around 12.50, and this suggests a recovery time of 13.25. This estimate can be checked with the Soyuz recoveries, which may have been subject to similar constraints. Soyuz 40 came down on 22 May at 13.58, while Soyuz T-4 came down on 26 May at 12.38. For 24 May, the corresponding landing time would have been 13.18, not taking into account the Cosmos 1267 ground track differing from that of Salyut 6.

To conclude, taking the launch time of Cosmos 929 as 17 July at 09.00 (1977) and that of Cosmos 1267 as 25' April at 02.01 (1981), the lifetimes of the recoverable vehicles are as noted below (in the case of Cosmos 929 one should remember that the landing time may be 89 minutes in error for the reasons already noted):

Kosmos 929 30d 10h 54m (16 August)

31d 10h 31m (17 August)

Kosmos 1267 29d 11 h 24m