Columbia returned to service in August 1989 after post-Challenger modifications with a classified mission for the Defense Department. As with the era's other military flights, details were withheld: the crew of five is understood to have deployed a satellite relaying data from reconnaissance spacecraft to the ground.
The five-day flight passed with little public fanfare, exactly as its planners intended. For Columbia, the oldest orbiter, the mission marked a quiet resumption of duty after a long stretch of upgrades, slotting it back into a fleet now sharing an intense schedule of satellite deployments, planetary launches and, increasingly, the science laboratories that would come to define its later career.
Columbia returned to flight in August 1989 after three and a half years on the ground — the oldest orbiter, extensively modified and largely left out of the post-Challenger recovery while the newer ships flew first. Its cargo was classified, and remains officially so.
Outside observers, tracking the orbit and watching what appeared afterwards, concluded the mission deployed a relay satellite serving the reconnaissance fleet — the intelligence community's equivalent of the TDRS network, allowing imaging satellites to send their take down without waiting to pass over a friendly ground station.
The flight is a good illustration of how much of the Shuttle's early life is simply undocumented. Of the programme's 135 missions, ten were flown entirely for the military, and for most of them the public record consists of a crew list and a set of times. The astronauts involved flew the same risks and did the same difficult work as their colleagues, without any of the recognition that normally came with it.
