A look at CNN's live broadcast of the Challenger shuttle launch on January 28, 1986.
Seven crew members died in the explosion, including Christa McAuliffe, who would have been the first teacher in space.
The explosion was a result of a rocket booster failure which ignited the fuel tank.
Some of the objectives of Mission STS-51L included the "Comet Halley Active Monitoring Program" (CHAMP), a fluid dynamics experiment, and lesson plans and telecasts by Christa McAuliffe.