OTD…Jan. 9 and STS-32

#OTD in 2002…Atlantis launched the outward expansion of the space station’s truss backbone

#OTD in 1997…Cassini was launched on its billion-mile trek to Saturn

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.