Astronauts and Cosmonauts celebrated in orbit today afterthe Shuttle Atlantis docked neatly with the Russian space station Mir. Overcoming his initial discomfort concerning a Russian custom, Atlantis commander Hoot Gibson presented Mir commander Vladimir Dezhurov with the traditional three carnations and three roses. In return, the Russian skipper gave the shuttle crew bread and salt. Spirits were high after this morning's highly difficult docking procedure went off without a hitch. Astronaut Norman Thagard, who has been working with the crew aboard the Russian station since mid-March, confessed to mixed emotions about hitching a ride back to Earth. "I'm ready to go home," he said, "but at the same time you think, well, I'd like to do this for just a while longer." A first priority for the Mir crew: showers. Water supplies aboard the Russian space station are so tightly limited that crew members can shower only once a month. Atlantis delivered water to Mir today.