Iml2 An International Triumph

On her last scheduled mission before a planned year-long overhaul, Columbia was again outfitted with the EDO equipment to support her crew for a fortnight aloft. Mounted in her payload bay for the sixth time was the European-built Spacelab module, this time devoted to a variety of life and microgravity science investigations and known as the second International Microgravity Laboratory (IML-2). As its name implies, the mission featured more than 70 experiments provided by 200 scientists from 13 countries, including the multinational ESA, together with Canada, France, Germany, Japan and the United States.

Unlike the IML-1 mission, flown on Space Shuttle Discovery in January 1992, the second flight was twice as long in duration and carried double the number of experiments and research facilities. Several of these were controlled remotely by ground-based scientists, with European and US research teams connected by intercontinental voice, video and data links. Such 'telescience' was seen as useful practice for running long-duration space station experiments. Further, said IML-2 Mission Manager Bob Snyder, ''with this amount of science, squeezed into a 14-day mission, it is critical to have both telescience and remote operations''.

In another indication of the importance of the experiments, and the need to squeeze as much scientific output from IML-2 as possible, Bob Cabana's crew was split into two 12-hour shifts to operate the laboratory around-the-clock. The Red Team comprised Cabana, Pilot Jim Halsell, Payload Commander Rick Hieb and Japanese Payload Specialist Chiaki Mukai, while their Blue counterparts included Mission Specialists Carl Walz, Leroy Chiao and Don Thomas. The inclusion of Mukai, who became the first female Japanese spacefarer and represented her country's National Space Development Agency (NASDA), highlighted Japan's immense contribution to the IML-2 mission.

The experiments spanned a wide range of the facilities in the Spacelab module, covering both life and microgravity sciences and highlighting the mission's international nature. Germany's Biostack, for example, sandwiched biological specimens between plates of radiation detectors as part of efforts to determine the impact of high-energy cosmic rays passing through the module's outer hull. The specimens were then examined after Columbia's landing to identify the paths and entry points of heavy ions and assess physical changes or damage. The impact of such radiation could, it was recognised, prove detrimental to astronauts on future long-duration space station or Mars trips.

The STS-65 crew gathers in the IML-2 module. Front row (left to right) are Chiaki

Mukai, Bob Cabana and Jim Halsell and back row are Rick Hieb, Don Thomas, Carl

Walz and Leroy Chiao.

Previous investigations had already confirmed that high-energy particles of solar and galactic origin, and their interaction with Earth's atmosphere, have potentially serious side-effects on living organisms. However, it is not possible to adequately measure these side-effects in ground-based laboratories because our planet's atmosphere - fortunately for us - filters out most of this radiation. During IML-2, three sealed Biostack containers were loaded with shrimp eggs and salad seeds to assess their reactions. Other radiation-measuring experiments were conducted using a Japanese-built monitoring device. Moreover, IML-2 marked the first occasion that such radiation data had been transmitted to Earth in real-time.

Such radiation data was not only important from the points of view of the astronauts themselves, but also the many other biological specimens, animals and fish who called Spacelab their home for the two weeks that Columbia was aloft. One particularly important life sciences facility was ESA's Biorack, which supported a wide range of investigations looking at the side-effects of microgravity and cosmic radiation on genetically modified rapeseed roots, cress seedlings, fruit flies and even human skin cells. Elsewhere in the module was the Aquatic Animal Experiment Unit (AAEU) with its complement of Japanese red-bellied newts, goldfish and Medaka fish.

Obviously, the 'perishable' nature of these living specimens meant that loading them on board Columbia could only take place a few hours before her launch on 8

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