STS-91 Day 8 Highlights

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On Tuesday, June 9, 1998, 6:00 a.m. CDT, STS-91 MCC Status Report # 14 reports:

With astronaut Andy Thomas aboard and on his way home, Discovery and crew will focus on science investigations today and participate in several special interviews and phone calls.

Following yesterday's undocking with the Russian Mir space station, crew members will each have a couple of hours off duty during the day as well to provide a brief rest break from the hectic pace of their flight.

Observations will continue today with the Alpha Magnetic Spectrometer (AMS) science instrument mounted in Discovery's payload bay. The 3 1/2 ton instrument is an innovative particle collector hoped to provide scientists with insight into the existence of dark matter and antimatter in the universe. Aboard Discovery, astronauts Franklin Chang-Diaz and Janet Kavandi are monitoring the experiment.

Also today, Pilot Dom Gorie and astronaut Wendy Lawrence will study the process of combustion in weightlessness using the Solid Surface Combustion Experiment (SSCE) in Discovery's cabin. The investigation studies how air motion affects the spread of flames. The convection currents that cause hot air to rise on Earth are not present in weightlessness, and fires burn differently.

Although the problem with high-rate communications will not allow television to be transmitted from Discovery, the crew will take part in several audio events with students and media today. At 6:26 a.m. Central, Commander Charlie Precourt and Chang-Diaz will answer questions from students in Lisbon, Portugal, and in Washington, D.C., in an event that will honor the 500th anniversary of Portuguese explorer Vasco De Gama's discovery of a sea route to India. Portugal also is a participant in the international AMS experiment aboard the shuttle.

At about 7:06 a.m., Thomas will offer thanks and congratulations to NASA operations personnel who have supported him at the Mission Control Center-Moscow in Korolev, Russia, through a special link-up. At 9:31 a.m. Central, reporters with the Mutual Broadcasting System, KMOX Radio in St. Louis and King TV in Seattle will have an opportunity to interview Precourt, Thomas, Chang-Diaz and Kavandi.

At 11:21 a.m Central, Precourt and Chang-Diaz will take a special phone call from Costa Rican President Dr. Miguel Angel Rodriguez, U.S. Ambassador to Costa Rica Thomas J. Dodd and Costa Rican scientists Dr. Bert Kohlmann and Sith Ying. Kohlmann leads the space research team that has conducted experiments on the shuttle that ma y help find insight into the illness of Chagras disease. Ying is a student at Earth College in Costa Rica who also has worked with NASA.

On Tuesday, June 9, 1998, 6:30 p.m. CDT, STS-91 MCC Status Report # 15 reports:

Following four busy days of docked operations with the Mir station, Discovery's crew enjoyed an afternoon of off -duty time today as they move into the home stretch of their flight.

This morning's activities included work with the Orbiter Space Vision System (OSVS) experiment, a system that creates a graphic digital display of the payload bay environment on laptop computers. The SVS equipment will be used during the assembly of the International Space Station to provide astronauts operating the Shuttle's mechanical arm with precise alignment information as station components are brought together.

The crew continued stowing items that were transferred over from the Mir for return to Earth and monitored some of the science experiments being carried on the flight. Additional tests were made of the Spacehab Universal Communications System (SHUCS), although the system is still experiencing problems with the ability of its antenna to find and hold communication with the satellites that support the experiment.

The Alpha Magnetic Spectrometer payload, located in Discovery's payload bay, was powered off for a period of time earlier today due to concerns that the payload might be getting too warm. After an adjustment was made to the orientation the Shuttle was flying in, thermal conditions improved. The AMS was subsequently powered back up and high rate data collection has resumed. The 3 1/2 ton instrument is an innovative particle collector hoped to provide scientists with insight into the existence of dark matter and antimatter in the universe. Aboard Discovery, astronauts Franklin Chang-Diaz and Janet Kavandi are monitoring the experiment.

While the crew enjoyed some time off, flight controllers reviewed a problem seen with the Shuttle's onboard computer system.

Last night while the crew was asleep, General Purpose Computer (GPC) #1 was supporting guidance, navigation and control requirements and GPC #4 was supporting systems management. Flight controllers noted that on GPC #1, within the software program supporting the Global Position Satellite operation, there was a growing discrepancy between where the GPS system was telling the Shuttle it was located and where the GPC had calculated the Shuttle should be. Resets of the GPS system software did not resolve the discrepancy. The cause of the discrepancy is not yet understood.

A decision was made to bring up a different computer to support Shuttle guidance and navigation with the GPS portion of the program turned off. Since doing that, all guidance and navigation activities have been nominal. The GPS portion of the navigation system remains powered off. Consideration is being given to installing a software patch for the guidance support program that would block out the GPS portion of the guidance software.

Discovery's crew will begin an eight-hour sleep period at 7:06 p.m. this evening and receive a wake-up call from Mission Control at 3:06 a.m. Central time tomorrow to begin their ninth day in space.

Discovery is currently in a 207 by 195 nm orbit, circling the Earth once every 91 minutes.

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