First called STA-099, Challenger was built to serve as a test vehicle for the space shuttle program.
In early 1979, NASA awarded shuttle orbiter manufacturer Rockwell a contract to convert STA-099 to a space-rated orbiter, OV-099. The vehicle's conversion began late that year. Nearly two years later, final assembly of Challenger started. Before installing its reentry-enabling thermal heat shield, fit-check tiles were fabricated and installed on the orbiter's body. These "stand-in" tiles were then referenced to manufacture their flight-ready counterparts. Challenger rolled out of its California assembly facility June 30, 1982.