Scientists are doing a little bit of astrophysics research as activities aboard the fourth U.S. Microgravity Payload (USMP-4) wind down in preparation for Friday morning's landing.
Astrophysics is not really a part of the bill for the mission, but it's an important part of ensuring that data are interpreted for the Confined Helium Experiment, said Peter Curreri, the mission scientist here at NASA's Marshall Space Flight Center.
CHeX used a dewar full of liquid helium to measure the finite size effect where materials behave as if they are two-dimensional. The sensitivity of the experiment is so great that even cosmic rays can add heat and disrupt the activities.
The liquid helium ran out of CHeX at 12 days, three hours mission elapsed time, which was just about when engineers predicted it would be depleted. However, scientists have left the instruments on to measure cosmic ray and background radiation effects. One area of special concern is the South Atlantic Anomaly where the Van Allen radiation belts dip closer to Earth.
The radiation measurements will be used in figuring out how much background heating noise should be subtracted when the CHeX data are analyzed. The data will also be useful for other missions that have electronics that might be affected by the South Atlantic Anomaly or by cosmic rays, Curreri said.
Only one other USMP-4 experiment, the Isothermal Dendritic Growth Experiment (IDGE), remains active, Curreri said. IDGE, and the Space Acceleration Monitoring System, will run through late Thursday when the USMP-4 is shut down in preparation for landing.
The MEPHISTO furnace shut down early Wednesday when it finished processing its samples. The Advanced Automated Directional Solidification Furnace (AADSF) was shut down early Tuesday when its last sample cartridge apparently broke, leaking vapor into the furnace proper which destroyed the thermocouples.
IDGE, CHeX, MEPHISTO, and AADSF all are mounted in the payload bay on a special multipurpose carrier.
Inside the shuttle, the three middeck glovebox experiments - Enclosed Laminar Flames, Particle Engulfing and Pushing, and Wetting Characteristics of Immiscibles - completed all of their planned runs, too.
"The glovebox investigators had just great results," Curreri said. This included having the crew revise procedures with the scientists when experiments ran differently than expected.
The science teams are writing their end-of-mission summaries, and a final science press conference will be held Thursday morning. We will publish the final science story Thursday afternoon.