What was the first space telescope built by NASA?
OAO-2 was the first NASA observatory to successfully launch and complete its mission from 1968 to 1973.
The first space observatory successfully launched by NASA and managed to remain in orbit for the duration of its mission was the Orbiting Astronomical Observatory - 2 (OAO-2, nicknamed Stargazer). It was launched into orbit on December 7, 1968 and remained in contact until January or 1973.
It had 2 experiment packages; the Smithsonian Astronomical Observatory (SAO) and the Wisconsin Experiment Package (WEP). SAO contained four 1 ft diameter telescopes for studying UV light and finished its mission in 1970. WEP contained eleven telescopes, also for studying UV. Its mission ended when contact was lost in 1973
OAO-2's predecessor, OAO-1 was successfully launched in 1966 but lost control in orbit after 3 days due to power failure.