OTD…Sept. 21 and Endeavour retirement

Today in 2011, shuttle Discovery made a graceful landing at Kennedy Space Center, returning from her final voyage after a remarkable three-decade life of service.

#OTD in 2007…NASA’s Dawn probe launched to explore the uncharted worlds of Vesta and Ceres in the heart of the asteroid belt.

Today in 1986…Space shuttle Challenger and her seven astronaut crew were lost during launch.