WITH the space shuttle Atlantis heading home, United States and Russian orbital activities will temporarily go their separate ways. But neither nation any longer views its manned spaceflight program in the old nationalistic perspective.
As Tommy Holloway, National Aeronautics and Space Administration manager for the shuttle-Mir missions put it, ''this is NASA's finest hour, and I expect it will continue for many years to come.'' For his part, Anatoly Solovyev, now commanding Russia's space station Mir, observed that a ''linking of ideas, wills, peoples in order to form a very great scientific program'' is taking place.
The successful US-Russian linkup is also the kind of achievement NASA needs to boost agency morale and underscore its manned spaceflight mission at a time when funding cuts are squeezing its operations.
''It's just one of the small milestones along a much greater journey,'' says Atlantis commander Robert Gibson. ''But at least we have begun that very long journey.'' Officials of both the American and Russian space programs have said they hope this will convince politicians to continue the trek.
It is one thing to plan to meld the national programs to begin building an international space station in 1997. It has been a quite different experience to see that planning become reality over the past week in the spectacularly successful Atlantis-Mir joining. That drove home the fact that these two spaceflight programs, which evolved quite separately, are indeed converging toward a united effort.
Robert Walker, chairman of the House Committee on Science, acknowledged this by noting that, 20 years after their first brief joint-space mission, ''America and Russia meet again in space. The knowledge to be gained from these activities is vital to a successful space station.''
The six American astronauts and two Russian cosmonauts on Atlantis were scheduled to land their spacecraft today at the Kennedy Space Center in Cape Canaveral, Fla. Astronaut Norman Thagard - the first American to serve on a Russian space facility - and his Mir team mates Vladimir Dezhurov and Gennady Strekalov were undergoing physiological tests to see how they had adapted to weightlessness. When they land, they will be the first Russian spaceflight team ever to be debriefed in the US.
Meanwhile, technicians at the Kennedy Space Center are preparing two other shuttles - Discovery and Endeavour - for launch later this summer. Discovery, with the woodpecker holes on its external fuel tank repaired, is due to take off July 13. It is to deploy a new tracking and data-relay satellite and conduct experiments. Endeavour's launch has been delayed for a third time, but is set for the end of July or early August.
Endeavour's mission is to deploy and retrieve two research satellites. One of these is the wake shield device that failed to operate properly in February 1994 during the first shuttle mission with a Russian cosmonaut - Sergie Krikalev - as a crew member.
On Mir, the new crew with Cosmonauts Solovyev and Nikolai Budarin is settling in for a duty tour that runs into September. For the first time ever, a Russian crew flew to the Russian station on an American spaceship. The cosmonaut's duties include a spacewalk to free a jammed solar array using tools brought by Atlantis.
They also will be preparing to receive European Space Agency astronaut Thomas Reiter, who is to begin a 135-day mission in August. For the first time in ESA-Russian joint-space missions, a European astronaut will act as flight engineer responsible for maintenance and operation of Mir.
Though European astronauts have flown on Russian craft for years, those efforts did not foresee uniting national programs like the shuttle-Mir project.