OTD…May 14 and Skylab

#OTD in 1995…Columbia launched on a microgravity science Spacelab flight

#OTD in 1994…Endeavour launched on the second Space Radar Laboratory mission

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.