DISCOVERY'S historic visit to the Mir space station turned out to be what its planners expected - a test of how well Russian and American flight control teams can work together.
Two separate control centers - linked only by voice and fax lines - overcame differences of language and tradition to bring off the mission's success.
Lack of intimate knowledge of each other's spacecraft gave way to a growing sense of mutual trust as the two teams ``worked the problem'' raised by Discovery's leaking maneuvering thrusters. Russian technicians were concerned that chunks of frozen fuel from Discovery's leaky jet would hurtle into the Soyuz spaceship - which is the cosmonauts' ride home - attached to Mir.
Engineers at the Houston control center conferred with engineers at the Kaliningrad center near Moscow to develop a plan for Discovery to approach Mir safely. Kaliningrad controllers gained enough confidence in the shuttle's capabilities to let it come within 37 feet of Mir on Feb. 6.
For the two teams, this was a successful beginning to a spate of seven shuttle-Mir missions over the next two years. Discovery's commander James Wetherbee appeared to have this in mind when he called the close-up view of Mir ``the most beautiful thing I've ever seen in space.''
BOTH Russian and United States space-flight officials wanted to test rendezvous procedures as much as possible before the shuttle Atlantis tries to dock with Mir in June. But the National Aeronautics and Space Administration has also stressed that the entire shuttle-Mir program is intended to help the two countries learn how to work together in space, leading up to an international space station with its Japanese, European, Canadian, US, and Russian personnel.
Therefore, the experience of coping with Discovery's thruster problem is as valuable as the rendezvous knowledge the mission has gained.
Dual control of shuttle-Mir missions requires trust and coordination. Russian controllers want the final stages of rendezvous and docking to take place within direct communication of a Russian ground station. Houston has main control of the maneuvering, since the shuttle is the active craft. But Russian controllers want to keep an eye on the process.
Therefore, Houston defers to Kaliningrad in matters that the Russians consider vital. On Feb. 5, Houston mission-operations director Randy Stone explained that his Russian counterparts were being ``very methodical and conservative'' because they didn't fully understand Discovery's capabilities. But he added that ``it's their call.''
With the more historic part of its mission over, Discovery has gone on to more basic scientific experiments and has released a 2,800-pound astronomy satellite. Discovery's eight-day flight is scheduled to end on Feb. 11.