It was already common practice on research missions of this type for the crew to work in two 12-hour shifts to maintain operations around-the-clock: the Red Team comprised Bowersox, Rominger, Thornton and Sacco, while the all-rookie Blues included Lopez-Alegria, Coleman and Leslie. As with USML-1, which carried two world-class research scientists as Payload Specialists, this second mission proved no exception: Sacco had developed several of the onboard zeolite crystal investigations, while Leslie helped to design a unit called the Geophysical Fluid Flow Cell (GFFC), which was intended to mimic the dynamics of planetary and stellar atmospheres.
''We're primarily researchers and scientists," Leslie said of the role of the Payload Specialist, ''and the disadvantage is that often you only fly once.'' The advantages, however, were that he received a flight assignment much more quickly than 'career' NASA astronauts: ''I went into the programme in 1994 and flew in '95. So it was fast!" He also added that, since he was on government business, he received extra pay, but after 'transport' and 'accommodation' deductions, this amounted to just a couple of dollars per day! ''You know the government," Leslie grinned. ''You can't go anywhere without travel orders!''
During the mission, Leslie had ample opportunity to work with the GFFC, which consisted of two 'hemispheres' - a baseball-sized one, made from stainless steel, mounted inside a larger, transparent one of sapphire - both of which were affixed to a turntable. A thin layer of silicone oil filled the gap between the hemispheres. During operations, the temperatures of both hemispheres, together with the rotation speed of the turntable, were minutely adjusted by the experiment's computer, which also introduced thermally driven motions into the oil. This allowed physicists to simulate and model fluid flows in the atmospheres of rotating stars and planets.
A similar experiment flew on Spacelab-3 in April 1985 and revealed several types of convection difficult to study on Earth, as well as enabling researchers to observe their structures, instabilities and turbulence. During USML-2, the GFFC was employed, among other tasks, to mimic conditions in Earth's 'mantle' - a region of predominantly magnesium-rich silicate rock sandwiched between the core and lithosphere, which undergoes solid-state flow - as well as plasma flows on the Sun. After activation late on 21 October, Principal Investigator John Hart and his team at the University of Colorado at Boulder controlled their experiment remotely from the ground.
Simulating plasma flows very close to the solar surface had been another of the investigations conducted during Spacelab-3 and research on Columbia 10 years later allowed them ''to compare USML-2 results with our previous experiment,'' said Hart. ''The instrument seems to be working great.'' It was hoped that data from GFFC would enable solar physicists to develop better computer models of fluid behaviour on the Sun. ''This is all kind of new and exciting stuff,'' Hart told journalists a few days later, as he watched time-lapse movies of simulated solar flows from the Spacelab module.
The movies were made from a series of still images, snapped every 45 seconds, as the fluids swirled between the unit's two rotating hemispheres. ''You can see a lot of the evolution of these solar dynamic flows we've been interested in, and we've seen some surprising turbulence," Hart told Columbia's crew. ''We are comparing these results with our computer simulations and other theoretical ideas to understand the extensive turbulence which starts near the polar region and spreads rapidly towards the equator."
Despite minor problems relaying temperature parameters to the GFFC, Leslie was happy with its performance, calling it ''a planet in a test tube.'' Later in the mission, efforts were made to simulate activity in Jupiter's atmosphere, which is of particular interest because this planet radiates significantly more heat than it receives from the Sun, contracting and liberating gravitational potential energy as heat. ''These early runs show dramatic changes in flow types, with very small variations in the instrument settings,'' said University of Colorado team member Scott Kittelman. This focus on mimicking solar and Jovian atmospheric dynamics continued throughout the mission.
''We hope this will give us ideas about the hidden inner atmosphere of Jupiter,'' said co-investigator Dan Ohlsen on 1 November. However, several experiments had applications that were potentially useful in understanding our own planet. ''We can isolate certain phenomena with the experiment,'' said Leslie during a news conference from orbit on 3 November, ''and take out some of the complicating things in terms of climate - things like rainfall and clouds.'' During each experiment, parameters such as voltage, rotation speed and temperature were adjusted to create unstable and turbulent flows to better explore the dynamics of both oceans and atmospheres.
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