STS-33

STS-33 was the 31st Space Shuttle mission and the tenth flight of the orbiter Discovery. It carried a classified payload for the U.S. Department of Defense, making it the sixth shuttle mission dedicated to the DoD. This flight was also the seventh since the Challenger disaster and the final shuttle mission of the 1980s. Because of the secret nature of the operation, most details about the payload remain undisclosed.

The mission was originally designated STS-33R to avoid data-tracking conflicts with earlier missions that used the same number sequence. Flights STS-26 through STS-33 after the disaster carried an "R" in official documentation for this reason.

Discovery launched from Kennedy Space Center's Launch Complex 39B on November 22, 1989, at 7:23:30 p.m. EST, marking the third night launch in shuttle history and the second since flights resumed in 1988. The launch was originally set for November 20 but was delayed by issues with the electronics controlling the solid rocket boosters' ignition and separation.

The crew included pilot John Blaha, who replaced S. David Griggs after Griggs was killed in a vintage aircraft crash in June 1989. Griggs is honored on the mission patch with a gold star. Mission specialist Sonny Carter, who flew on this mission, later died in a commercial plane crash in April 1991 while training for STS-42.

During the flight, Discovery deployed a single satellite, designated USA-48. Experts believe it was a secret Magnum ELINT satellite destined for geosynchronous orbit, similar to the one launched on STS-51-C in 1985. According to ABC News, the satellite was meant to intercept communications from the Soviet Union, China, and other communist states, and it replaced an earlier satellite running low on station-keeping fuel. However, astronaut Gary E. Payton stated in 2009 that the STS-51-C payload was still operational.

Aviation Week reported that Discovery first entered a 204 km by 519 km orbit at a 28.45° inclination. Three OMS burns followed, the last on the fourth orbit, circularizing the orbit at 519 km. The satellite was deployed on the seventh orbit, and its Inertial Upper Stage fired at the ascending node of the eighth orbit, placing it into geostationary transfer orbit. This was the eighth IUS launched from a shuttle and the seventh successful deployment.