<Tr> <Th> Epoch </Th> <Td> Planned </Td> </Tr> <Tr> <Td_colspan="2"> <P> </P> Space Shuttle program ← STS - 61 - C STS - 26 → </Td> </Tr> <P> STS - 51 - L was the 25th mission of the United States Space Shuttle program, and disastrous final mission of the Space Shuttle Challenger . The mission to carry out several lessons from space and observe Halley's Comet never made its target landing date of February 3, 1986 . A structural failure during its ascent phase 73 seconds after launch on January 28 from Kennedy Space Center Launch Complex 39 killed all seven crew members--Commander Dick Scobee, Pilot Michael J. Smith, Mission Specialists Ellison S. Onizuka, Judith A. Resnik and Ronald E. McNair, and Payload Specialists Gregory Jarvis and Christa McAuliffe--and destroyed the orbiter . The Rogers Commission determined that the cause of the destruction was due to the failure of an O - ring seal on the starboard Solid Rocket Booster (SRB). Space Shuttle flights were suspended for 32 months while the hazards with the shuttle were addressed . </P> <P> The tenth mission for Challenger, STS - 51 - L was scheduled to deploy the second in a series of Tracking and Data Relay Satellites, carry out the first flight of the Shuttle - Pointed Tool for Astronomy (SPARTAN - 203) / Halley's Comet Experiment Deployable in order to observe Halley's Comet, and carry out several lessons from space as part of the Teacher in Space Project and Shuttle Student Involvement Program (SSIP). The flight marked the first American orbital mission to involve in - flight fatalities . It was also the first American human spaceflight mission to launch and fail to reach space; the first such mission in the world had been the Soviet Soyuz 18a mission, in which the two crew members had survived . Gregory Jarvis was originally scheduled to fly on the previous shuttle flight (STS - 61 - C), but he was reassigned to this flight and replaced by Congressman Bill Nelson . </P>

What was the purpose of the last challenger mission