MISSION CONTROL CENTER STATUS REPORT #12
STS-91
MONDAY, JUNE 8, 1998 - 6 a.m. CDT

The STS-91 astronauts and the Mir 25 cosmonauts will part company today,
with the Space Shuttle Discovery scheduled to undock from the station at
11:01 a.m. Central time, officially ending the three years of shuttle
dockings and astronaut flights aboard the Russian complex.

Discovery will be bringing home astronaut Andy Thomas, who has been in
space since Jan. 22. If Discovery lands as planned on Friday, the seven
Americans who have stayed aboard Mir will have spent a combined total of
977 days in space.

Discovery's crew was awakened at 3:06 a.m. Central today to "Manic
Monday" performed by The Bangles, played to the crew by Mission Control
in honor of an historic Monday for the U.S. and Russian space programs.
Today's schedule includes possible television from the Mir of a final
crew farewell and hatch closing at 7:51 a.m. Central; possible
television of Discovery's undocking from Mir at 11:01 a.m. Central as
the spacecraft fly above Russia, southwest of Moscow and north of the
Ukrainian border; possible television of Discovery's flyaround of the
Mir at 12:05 p.m. Central; and possible television scenes from the
shuttle through U.S. ground communications stations at 3:22 p.m.
Central.

During the four days Discovery has been docked to the Mir, more than
1,100 pounds of water and almost 4,700 pounds of cargo, experiments and
supplies have been exchanged between the two spacecraft.

After undocking, the shuttle will back away from the Mir until it
reaches a distance of approximately 240 feet below the station. Pilot
Dom Gorie will then perform a nose forward flyaround of Mir. About 20
minutes after undocking, as Discovery reaches a point about 240 feet
directly in front of the Mir, Mir 25 Commander Talgat Musabayev and
Flight Engineer Nikolai Budarin will release a tracer gas of acetone and
biacetyl into the depressurized Spektr module. The gas release into the
damaged module will begin about three minutes before sunrise and should
last about 20 minutes, hopefully enabling Discovery's astronauts to
document the dull green, luminescent gas as it passes through the hole
in the Spektr module's hull. The test is hoped to pinpoint the location
of the breach in the Spektr that resulted from last year's collision of
a Progress cargo ship. Finally, almost an hour and a half after
undocking, Gorie will fire Discovery's jets as the shuttle passes
directly above the Mir to separate from the vicinity of the Russian
station.

After undocking, experiment work will continue aboard Discovery,
including Alpha Magnetic Spectrometer (AMS) science operations and
checks of the Spacehab Universal Communications System (SHUCS) system.
The AMS instrument is hoped to provide scientists insight into the
existence of dark matter and antimatter in the universe. The SHUCS is a
communications system which may allow future scientists to communicate
directly with astronauts conducting experiments in the Spacehab module.

The Discovery-Mir space complex is orbiting the Earth at an altitude of
239 statute miles with all systems ready to support undocking. The next
STS-91 status report will be issued at about 6 p.m. Central time Monday.
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