Date: Mon, 8 Jun 1998 18:49:49 -0500
Subject: STS-91 Status Report # 13


Three years after Space Shuttle Atlantis accomplished the first docking
to the  Mir space station,  the STS-91 crew aboard Discovery undocked
from the orbiting Russian complex this morning to conclude the ninth and
final Shuttle-Mir mission.   Joining the STS-91 crew for the trip home
is NASA astronaut Andrew Thomas, the seventh and final astronaut to
serve as a station crew member, returning home after four and a half
months in space.

After the hatches between the two vehicles were closed for the final
time at 8:07 a.m., the Shuttle and Mir separated on time at 11:01 a.m.
CDT while flying above Russia, southwest of Moscow and north of the
Ukrainian border.  Following separation, STS-91 Pilot Dom Gorie
maneuvered the shuttle away from the Mir to a distance of approximately
2403,000 feet below the station.  He then performed a nose-forward
fly-around of Mir allowing the Shuttle to reach a point about 240 feet
directly in front of the Mir at 11:24 a.m.  

With Discovery stationkeeping at that position,  Mir 25 Commander Talgat
Musabayev and Flight Engineer Nikolai Budarin  then released a tracer
gas of acetone and biacetyl into the depressurized Spektr module.  The
gas release was done in the hope that the STS-91 crew would be able to
see the fluorescent substance as it passed through the hole in the
Spektr module's hull, pinpointing the location of the breach in the
Spektr that resulted from last year's collision of a Progress cargo
ship. No leak source was seen by Discovery's crew.

Finally, at 12:27 p.m., Gorie fired Discovery's maneuvering jets as the
shuttle passed directly above the Mir to separate from the vicinity of
the Russian station.  As of 6 p.m. CDT this evening, Discovery was 28
nautical miles ahead of the Mir with the distance between the two
spacecraft growing at eight n.m. each orbit.

Discovery's crew spent the remainder of its seventh day in space stowing
items transferred from the Mir in preparation for Friday's landing at
the Kennedy Space Center.  The crew also continued experiment work,
including  the Alpha Magnetic Spectrometer (AMS) science operations and
checks of the Spacehab Universal Communications System (SHUCS) system.
Scientists hope the AMS will provide insight into the existence of dark
matter and antimatter in the universe. The SHUCS communications system,
designed to send and receive telephone voice and data communications
globally via three ground stations and the INMARSAT satellite system,
continues to experience difficulties.  The SHUCS payload team plans to
continue troubleshooting and testing of the system tomorrow.

The next STS-91 status report will be issued at about 6 a.m. Central
time Tuesday.