Bittersweet Voyage

On 2 December, Kregel told a journalist from the Orlando Sentinel that Chawla had taken the events in her stride, refusing to discuss blame. ''We'd be very foolish if we tried to second-guess or tried to figure out what the actual turn of events were without having all the information,'' he said. ''We're six folks up here, we know what happened on our side, we'll get together with the folks on the ground and we'll put the whole story together and make sure it never happens again. Sure, we're always a bit disappointed if we don't get the full mission accomplished, but we did retrieve the satellite, and so the important thing is we're bringing Spartan back down to Earth and it'll get to fly another day.'' Floating at Kregel's shoulder, Scott agreed: ''We think it's more important to get the spacecraft back, refurbish it and fly it again. After all, the Sun will be there and we don't want to risk losing the satellite altogether.''

Whatever the exact cause of the failure was, Flight Director John Shannon confirmed on 4 December that NASA had formed an investigative team. ''We are planning to impound the Spartan after landing and the crew will be part of the investigation process,'' he said. Some engineers at KSC believed that the fiasco was due to an oversight by Chawla, although Lee Briscoe came to her defence by speculating that a Payload General Support Computer (PGSC) could have malfunctioned and prevented her inputted commands from reaching the satellite properly.

''The guys have gone back and looked at the data, they've dumped the PGSC log files and when they look at [those], they don't see some of the indications there that the command was issued to the spacecraft that puts it in the mode to be ready to deploy,'' Briscoe said. ''Did the crew miss that step? That's a possibility. Was there something in the PGSC software that didn't issue it? That's a possibility.''

As discussions, and private recriminations, got underway on the ground, the crew pressed on with the last few days of what had otherwise proved to be a highly successful mission. In addition to USMP-4 operations and Scott and Doi's two spacewalks, a number of other scientific investigations were carried out. One of these was the Collaborative Ukrainian Experiment (CUE), under Kadenyuk's supervision, which explored the impact of the space environment on the pollination and fertilisation of Brassica rapa (turnip) and soybean seedlings.

Watching the experiment, and participating in identical 'control' studies on the ground, were around half a million students and teachers in the United States and over 20,000 others in Ukraine. The underlying objective of CUE was to develop an understanding of how to grow food plants in microgravity, which will prove highly desirable in future years when long-duration missions to the Moon or Mars become a reality, and key focal points included comparing ultrastructural changes, biochemical composition and functional differences in space.

The experiment was approved and signed by then-NASA Administrator Dan Goldin and his counterpart Alexander Negoda of the National Space Agency of Ukraine in 1995; later that same year, then-President Bill Clinton announced that a cosmonaut would accompany CUE on its Shuttle flight. Two years later, Leonid Kadenyuk was assigned to join Kregel's STS-87 crew, with Yaroslav Pustovyi backing him up and performing control experiments in parallel on the ground. In general, the plants returned to Earth were healthy, but some were smaller than expected, averaging 4 or 5 cm long rather than the 12 cm that was hoped for.

Leonid Kadenyuk tends seedlings as part of the Collaborative Ukrainian Experiment (CUE) in Columbia's middeck.

Other experiments mounted in Columbia's payload bay included a passive heat pipe being flown to validate technologies for upcoming space missions and an evaluation of a new sodium-sulphur battery cell for future geosynchronous- and low-Earth-orbiting satellites. Elsewhere, housed in a GAS canister, was a study of the characteristics of transitional and turbulent gas-jet diffusion flames; such research could not be conducted on Earth because gravity-driven buoyancy introduced flow instabilities. Two final sensors - the Shuttle Ozone Limb Sounding Experiment (SOLSE) and Limb Ozone Retrieval Experiment (LORE) - investigated the distribution of ozone and measured changes in atmospheric composition in high resolution.

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