STS-75 Day 8 Highlights
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- On Thursday, February 29, 1996, 9 a.m. CST, STS-75 MCC Status Report # 15
- Columbia's crew continues its work with the United States
Microgravity Payload experiments supporting a variety of
investigations including crystal growth, materials solidification and
fluid dynamics. Meanwhile, payload controllers continue to obtain
snapshots of data from the tethered satellite as it passes within
range of available groundstations around the world.
- As TSS battery power diminishes, plans are in work to turn on
science instruments, Earth sensors and stabilizing gyros in
anticipation of the closest approach of TSS to Columbia at about 11
p.m. central time today (approximately 07/08:50 mission elapsed
time). At that point, the orbiter should pass within about 50 miles of
the satellite possibly allowing payload bay instruments a chance to
gather data on the satellite as well.
- Because of the instability of the satellite and its varying
gravitational drag, the distance between the two spacecraft and the
time of closest approach likely will change. In any case, there is no
concern about Columbia passing too close to the satellite. Whether or
not the crew can visually observe the satellite during the fly-by will
depend on lighting conditions at that time.
- The Tethered Satellite is currently about 3,000 nautical miles ahead
of Columbia with the distance between the two spacecraft closing at
the rate of 340 nm with every revolution of the Earth.
- On Thursday, February 29, 1996, 6 a.m. CST, STS-75 Payload Status Report # 13
reports: (6/15:42 MET)
- The third United States Microgravity Payload (USMP-3) completed
another night of successful operations aboard the Space Shuttle
Columbia, with the four experiments that make up the payload
processing good data in the microgravity environment of Earth's orbit.
The smooth ride aboard Columbia, in free fall around Earth, was made
even smoother yesterday as crew members restricted their movements in
"quiescent" periods. This allowed USMP-3 researchers with the
MEPHISTO experiment to gather baseline data about the effects of
movement on their delicate semiconductor material samples by comparing
them to times of no activity.
- The scientific activities of the MEPHISTO experiment, led by
Dr. Jean-Jacques Favier of the French Atomic Energy Commission,
included a study of "g-jitter," or microgravity disturbance effects
such as those caused by crew activities and orbiter thruster firings.
As expected, the first 25-second thruster firing, or "burn," produced
accelerations of more than 10,000 micro-g's, a force equal to one-
hundredth of Earth's gravity, and provided a significant response in
the experiment's real-time data transmission. Another 15- second
firing also produced a marked change in this signal. The science team
observed that the measurements continued to increase for a few minutes
after each of these burns before slowly decreasing. Before and after
each thruster firing, the crew remained in a relatively still mode to
allow scientists to perform real-time correlations of MEPHISTO's data
with information collected from the Space Acceleration Measurement
System (SAMS) aboard the Shuttle.
- The understanding gained from the MEPHISTO experiment may ultimately
lead to improvements in materials preparation and processing on Earth.
MEPHISTO uses very selective methods to study the role of
gravity-driven fluid flows in the solidification of materials.
Microgravity reduces fluid flows caused by sinking and rising,
allowing researchers to explore effects normally hidden by gravity.
- This morning, the Marshall Space Flight Center's Advanced Automated
Directional Solidification Furnace (AADSF) began its first experiment
operations, melting a lead-tin-telluride sample to test theories about
gravity's effects on growing semiconductor materials. Today, the
instrument's science team, led by Principal Investigator Dr. Archie
Fripp, will continue melting and positioning all three samples, then
actually start growing crystals by seeding and re-solidifying the
- Yesterday afternoon, Pilot Scott Horowitz and Mission Specialist
Claude Nicollier performed runs of the Lewis Research Center-managed
Forced Flow Flamespreading Test (FFFT) experiment in the Middeck
Glovebox Facility. They burned flat paper samples to help the science
team, led by Glovebox Investigator Kurt Sacksteder, study how air
motion affects flame spreading in microgravity.
- Scientists who study combustion want to know the details of how air
motion affects flame spreading and how to better control fires that
may occur on orbit. On Earth, gravity causes hot air to rise and cool
air to fall. Because of the complexity of the physical and chemical
processes involved, the theoretical understanding of flame spreading
in space is still a relatively new science. The microgravity
environment available in the self-contained Glovebox aboard the Space
Shuttle is an important tool for scientists and engineers to study
this important phenomenon.
- The Isothermal Dendritic Growth Experiment (IDGE), developed by the
Rensselaer Polytechnic Institute, has completed 15 dendrite growth
cycles during its primary science phase. Images of free-floating
dendrites, acquired during melting after a growth cycle, show no
detectable motion compared with images of dendrites attached to the
experiment's container. Analysis of such post-melting images help
researchers define the mobility limits of the free-floating, pine
tree-shaped dendrite crystals in the microgravity environment.
- The ZENO Critical Fluid Light Scattering Experiment's sample cell
temperature continues to approach the critical temperature and
pressure at which xenon exists simultaneously in both the liquid and
vapor phases. ZENO uses precise light-scattering measurements as an
unintrusive way of seeing changes in a xenon sample as it fluctuates
rapidly between two states of matter.
- In addition to continued sample processing by the four USMP-3
investigations, the next 12-hours will begin with the first in a
series of Comparative Soot Diagnostics combustion experiment runs in
the Middeck Glovebox.
- On Thursday, February 29, 1996, 5 p.m. CST, STS-75 MCC Status Report # 16
- Columbia and the Tethered Satellite will pass within about 51
nautical miles of each other at 11:17 p.m. central time today
(approximately 7/08:59 MET), providing the astronauts a chance to
glimpse the errant spacecraft since it separated from the orbiter
- Tonight's encounter with TSS marks the point of closest approach for
the two spacecraft before they begin to separate once again.
Currently, the orbiter trails TSS by a distance of about 1900 nautical
miles, with Columbia closing on the satellite at the rate of 340 nm
with each revolution of the Earth. Whether or not the crew will be
able to see the satellite during the fly-by will depend on lighting
conditions and orbiter position.
- This afternoon, crewmembers discussed the progress of the flight
during an in-flight interview with two Philadelphia television
stations. A second interview, at 6:08 p.m., is with the United States
Information Agency's Worldnet program.
- Columbia is functioning normally, with no problems being tracked by
the flight control team as the Shuttle orbits the Earth every 90
minutes at an altitude of 180 statute miles.
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