Mir 25/NASA 7 Status Report NASA Release for March 27, 1998 MISSION CONTROL CENTER, Korolev - U.S. Astronaut Andy Thomas and his Mir 25 crewmates, Commander Talgat Musabayev and Flight Engineer Nikolai Budarin, commemorated two important space anniversaries this week. Tuesday, March 24, 1998, marked two years of continuous US presence aboard Mir. On March 24, 1996, at 4:30 p.m., Dr. Shannon Lucid officially became a Mir crew member when she transferred from the Space Shuttle to the Mir space station. (Dr. Norm Thagard was the first U.S. astronaut on Mir; he arrived on Mir March 14, 1995, and stayed 116 days in space.) Friday, March 27, 1998, marked an important but solemn day -- the 30th anniversary of the death of Cosmonaut Yuri Gagarin. On April 12, 1961, Gagarin became the first human to escape Earth's atmosphere and orbit the planet, and April 12th is still celebrated in Russia as Cosmonautics Day. As Thomas continued his science program, Musabayev and Budarin began preparation for next week's space walk. On Friday the crew was scheduled to spend about nine hours in the airlock preparing for the space walk. Plans called for the cosmonauts to replace old ancillary latches on the hatch with new latches which were brought up by the Progress resupply ship. Prior to any space walk, crew activities include a review with Russian ground controllers of the procedures to be used, a check of their space suits, medical checks, and a suited dry run of the space walk. Next Wednesday, April 1, the crew will go outside the space station to reinforce the damaged solar array on the Spektr module. That space walk had been scheduled for March 3, but was postponed when one latch on the Kvant-2 airlock hatch refused to unlatch. The problem has since been corrected. The hatch is scheduled to open at 8:20 a.m. EST. The space walk should last a little under 6 hours. Once the damaged solar array is braced, the crew will perform four additional space walks to replace the propulsion system for the Mir's boom jet assembly (known as the "Sofora"). The old propulsion system atop the boom which rises from the Kvant-1 module has been operating since its delivery to the station in August 1992, and is almost depleted of fuel. The series of space walks by Musabayev and Budarin to replace the boom jet assembly will begin April 6. The space walks will be spaced approximately five days apart and will last from five to six hours each. Besides preparing for next week's space walk, the crew performed various maintenance tasks this week. On Wednesday, they completed repairs on the trace contaminant removal unit. Replacement parts, including a new valve and charcoal filter, were brought up on the previous Progress. The crew reported that there was no visible damage to the old charcoal filter after hot air had accidentally been blown over the unit a few weeks ago. The station's air conditioning system continued to experience difficulty starting this week, but the crew was able to start it on every attempt. Russian ground controllers are investigating possible causes of these difficulties. Meanwhile, Thomas is continuing his scientific research program. This week he continued an immunity experiment, for which he is periodically taking blood and saliva samples. This life science investigation is designed to study and compare the human body's ability to produce antibodies to fight illness in a microgravity environment with the body's ability to produce antibodies on Earth. Previous research has indicated that some of the human body's immune responses appear to be suppressed during long duration space flight. Understanding the effects of space flight on the human body's immune system may be important in protecting the health of future space travelers on long duration flights. Astronauts Shannon Lucid, John Blaha, Jerry Linenger, and David Wolf also participated in this investigation during their research aboard Mir. Thomas also continued to troubleshoot the Biotechnology System Co-Culture (COCULT) experiment, designed to grow two different cell types in order to form three dimensional tissue samples in microgravity. Thomas processed seven samples for the material science experiment QUELD, the Queens University Experiment in Liquid Diffusion. This is a joint U.S., Canadian, and Russian experiment that uses a special furnace to analyze the phenomenon of diffusion. Diffusion is the slow mixing of materials by the random movement of molecules of one substance into another. While commonplace, the physical process of diffusion is not completely understood. Researchers hope to learn more about this process by studying diffusion in a microgravity environment. Science investigations by Thomas on Mir are part of 27 studies in the areas of Advanced Technology, Earth Sciences, Human Life Sciences, Microgravity Research, and International Space Station Risk Mitigation. The investigations are a combination of experiments performed on previous Mir missions as well as new research. Thomas has reached the half-way mark in his mission, having completed his ninth week aboard Mir and with nine more weeks to go before completing his mission in early June. He is scheduled to return to Earth aboard the Shuttle Discovery during the STS-91 docking mission to the Mir. He is the seventh and final NASA astronaut scheduled to live and work aboard the complex.