karn (04/05/83)
As many of you may know, there was a serious problem with the TDRS/IUS payload after separation from the Challenger last night. I am currently listening to a press conference in which it now appears that the problem occurred in the second stage IUS burn, the burn which was supposed to circularize the orbit at geostationary altitude. Telemetry was lost during the burn, but it was reacquired this morning. The resulting orbit should have been geostationary, but currently has an orbit inclination of about 2.4 degrees and a perigee of about 12,000 miles. Contrary to earlier reports, it appears that separation from the IUS did occur properly and the TDRS spacecraft oriented itself properly despite a relatively high attitude rotation rate imparted by the IUS. The spacecraft itself is in relatively good shape. The reason for the IUS anomaly is not yet known. It is currently anticipated that the spacecraft can put itself into a geostationary orbit over the next several days by using several hundred pounds of hydrazine stationkeeping fuel. The total loading was 1,300 pounds. [My guess is that this will work but limit the operational lifetime of the spacecraft somewhat.] Phil Karn