The B4/B5 Satellite was launched on 3 Oct 85. This mission was the first and only DSCS satellites launched on the space shuttle.
The B4 and B5 satellites were lifted into geosynchronous orbit by the Inertial Upper Stage (IUS). These were the first production DSCS III satellites built.
It was also the first DSCS III that carried an SHF downlink for the Single Channel Transponder (SCT).
Three months later the Challenger disaster happened and changed
how all DSCS IIIs would be launched. No other DSCS IIIs would be launched aboard a Space Shuttle. The next DSCS III
launch would not occur for another four years.