STS-93, Mission Control Center
Status Report # 07

Sunday, July 25, 1999, 7 p.m. CDT

The five astronauts aboard the Space Shuttle Columbia began their
fourth flight day at 4:31 p.m. CDT, preparing to make additional celestial
observations through the shuttle's windows and continue work with a
variety of experiments.

The day started off with a wake-up call sent up in honor of Pilot Jeff
Ashby. It was a song called "Some Day Soon," written by Judy Collins
and performed by Suzy Boguss.

The first job for Ashby and Mission Specialists Steve Hawley and Michel
Tognini was to set up an exercise treadmill and the Treadmill Vibration
Information System (TVIS) which will measure vibrations and changes in
microgravity levels caused by on-orbit workouts. These workouts are
needed to maintain astronauts' cardiovascular fitness and muscle tone,
which can suffer in the absence of gravity. Each crewmember was
scheduled to take a turn on the treadmill before it is put away at the end
of the day.

Astronomer Hawley once again is scheduled to make observations of
Jupiter, Venus and the Moon with the Southwest Ultraviolet Imaging
System (SWUIS) as Commander Eileen Collins and Ashby put the
shuttle in the proper orientation for his observations.

Tognini and Mission Specialist Cady Coleman will check on the
bioprocessing experiments, and harvest mouse-ear cress plants as part
of the Plant Growth Investigations in Microgravity experiment. These
genetically engineered plants are expected to yield clues to the sensitive
mechanisms the plants use to monitor their environment and help
scientists develop plants that respond better to the stresses of space
flight.

Collins and Ashby will fire the shuttle's engines so that the sophisticated
sensors of the Midcourse Space Experiment (MSX) satellite will be able
to collect ultraviolet, infrared and visible light data on the firing. The
satellite was launched from Vandenberg Air Force Base in California in
1996. The commander and pilot also will practice landings on a laptop
computer, simulation software and joystick combination called the
Portable In-Flight Landing Operations Trainer (PILOT).

Meanwhile, Mission Operations' Wayne Hale reported that engineers on
the ground continue to evaluate the short in one of the shuttle’s electrical
systems, which occurred shortly after launch as well as the slightly
reduced performance of the main engines. Neither problem poses any
risk to the remainder of the mission, Hale said.

Hale said the crew's discovery that a circuit breaker had popped during
the climb to orbit provides reassurance that the problem has been
isolated and will not affect any of the shuttle's other electrical systems
used for reentry and landing. He also said that the right engine's reduced
performance may have been due to a small hydrogen leak in tubes that
help cool the nozzle. While it won't be confirmed until the shuttle returns to
Earth, Hale said the evidence pointing to the leak includes a slightly
higher than normal temperature in that engine, and launch photos
showing a white streak that could be escaping hydrogen.

At this point, Columbia is flying smoothly, orbiting the Earth every 90
minutes at an altitude of 182 statute miles.

The next STS-93 status report will be issued about 6 a.m. CDT Monday.