(Above) Space Shuttle Discovery orbits above Earth in bottom-to-sun attitude, moments after TDRS-C’s release into space. TDRS-C is seen just below open payload bay (PLB). This artwork was done by Pat Rawlings for NASA.

This artist’s concept drawing depicts the Tracking and Data Relay Satellite-C (TDRS-C), which was the primary payload of the Space Shuttle Discovery on the STS-26 mission, launched on September 29, 1988.

STS-26 was the first Shuttle mission after the 1986 Challenger disaster. Challenger exploded 73 seconds after liftoff killing the crew and destroying the vehicle. Cause of the explosion was determined to be an O-ring failure in right SRB. Cold weather was a contributing factor.

The TDRS system provides almost uninterrupted communications with Earth-orbiting Shuttles and satellites, and had replaced the intermittent coverage provided by globe-encircling ground tracking stations used during the early space program. The TDRS can transmit and receive data, and track a user spacecraft in a low Earth orbit. The deployment of TDRS-G on the STS-70 mission being the latest in the series, NASA has successfully launched six TDRSs.