Chapter 2

Chapter II - Events Leading up to the Challenger Mission

Preparations for the launch of mission 51-L were not unusual, though they were complicated by changes in the launch schedule. The sequence of complex, interrelated steps involved in producing the detailed
schedule and supporting logistics necessary for a successful mission always requires intense effort and close coordination.

Flight 51-L of the Challenger was originally scheduled for July,
1985, but by the time the crew was assigned in January, 1985, launch had been postponed to late November to accommodate changes in
payloads. The launch was subsequently delayed further and finally
rescheduled for late January, 1986.

After a series of payload changes, the Challenger cargo included two satellites in the cargo bay and equipment in the crew compartment for experimetns that would be carried out during the mission. The
payloads flown on mission 51-L are listed in this table:

Mission 51-L Payloads
Tracking and Data Relay Satellite-B
Spartan-Halley Satellite
Comet Halley Active Monitoring Program
Fluid Dynamics Experiment
Phase Partitioning Experiment
Teacher in Space Project
Shuttle Student Involvement Program
Radiation Monitoring Experiment

The primary payloads were the Tracking and Data Relay Satellite (a
NASA communications satellite0 and the Spartan satellite that would be deployed into orbit carrying special instruments for the observation of Halley's Comet.

The NASA communications satellite was to have been placed in a
geosynchronous orbit with the aid of a booster called the Inertial
Upper Stage. The satellite would have supported communications with the Space Shuttle and up to 23 other spacecraft.

The Spartan satellite was to have been deployed into low Earth orbit using the remote manipulator system. The Spartan instruments would
have watched Halley's Comet when it was too close to the Sun for other observatories to do so. Subsequently, the satellite would have been retrieved and returned to Earth in the Shuttle payload bay.

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