STS-29R

The mission's primary payload was a Tracking and Data Relay Satellite (TDRS-D), which became TDRS-4 after deployment, and its attached Inertial Upper Stage (IUS). The satellite was deployed from the shuttle's payload bay less than six hours after launch, at 3:12 am EST. The first-stage orbit burn of the IUS took place an hour later, and the second burn to circularize the orbit occurred 12 hours and 30 minutes into the mission. The satellite was stationed at 41 degrees west longitude. Discovery also carried eight secondary payloads, including two Shuttle Student Involvement Program experiments. One student experiment, using four live rats with tiny pieces of bone removed from their bodies, was to test whether the environmental effects of space flight inhibit bone healing. The other student experiment was to fly 32 chicken eggs to determine the effects of space flight on fertilized chicken embryos.