STS-75 Mission Control Center 
Status Report # 28

Thursday, March 7 -- 4 p.m. CST

Columbia's astronauts have readied their ship to return to Earth after
a journey of more than 6 million miles.  Landing at the Kennedy Space
Center is targeted for 7:52 a.m.  central time, the first of two
opportunities to KSC tomorrow.

Early this morning, during the standard pre-landing check of
Columbia's flight control system, one of four data channels
failed. The command path involved is one of four that commands an
actuator to move flight control surfaces during reentry.  The command
path is considered "failed", but the three remaining command
paths remain healthy and in position to support tomorrow's planned
landing.

Throughout the night, the reentry flight control team will continue to
review weather conditions at the primary landing site at KSC, as well
as the alternate landing site at Edwards Air Force Base in California.

Flight controllers opted to forego an earlier KSC landing opportunity
at 6:16 a.m. central time, because of forecast low clouds and the
possibility of rain and gusty winds.  Weather conditions are expected
to improve later in the morning to support the two KSC landing
opportunities.

The first landing opportunity would see a deorbit firing of
Columbia's engines at 6:49 a.m.  central time, with a landing on
Runway 33 at 7:52 a.m.  The second opportunity, one orbit later, has a
deorbit burn at 8:25 a.m., followed by landing at 9:27 a.m.

If weather precludes a landing at KSC, there are two opportunities for
a Friday landing at Edwards Air Force Base.  The first would see a
deorbit burn of Columbia's engines at 8:15 a.m. central time, with
landing on Runway 22 at 9:27 a.m.  The second opportunity, has a
deorbit burn at 9:54 a.m. central time with landing at 10:54 a.m.
Weather in California is predicted to be acceptable to support
landing.

If Columbia remains in orbit an additional day due to weather
conditions, there are three landing opportunities available on
Saturday at KSC and three at Edwards.

The JSC newsroom will close at 5 p.m. and will reopen at 6 a.m. Friday
to support Columbia's planned landing.

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