OTD…May 15 and Faith 7

#OTD in 1992…Discovery launched with the first International Microgravity Laboratory.

#OTD in 1993…Endeavour launched a new NASA Tracking and Data Relay Satellite.

Today marks the 40th anniversary — July 20, 1976 — of the first U.S. robotic landing on another planet by the Viking 1 spacecraft on Mars.