STS-75 Day 2 Highlights

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On Friday, February 23, 1996, 7 a.m. CST, STS-75 MCC Status Report # 02 reports:

Setting up shop was the order of business aboard Columbia overnight and early Friday as the seven astronauts split into three shifts to support the many experiments scheduled throughout the 14-day mission.

Much of the astronauts' time was spent verifying the health of the Tethered Satellite System in anticipation of its scheduled deployment Saturday afternoon. The 1,400 pound satellite will be deployed to a distance of almost 13 miles while it remains attached to its support structure in the orbiter's payload bay by a pencil-thin cable. TSS deployment is currently scheduled for Saturday at 2:37 p.m. Central time.

Before turning in for his first on-orbit sleep period, Mission Specialist Jeff Hoffman tested the latching mechanisms that secure the satellite atop its docking ring on an extendable boom structure. These latches will be released just prior to the start of the six hour process to reel out the satellite.

The crew also checked out and activated several other experiments that will be carried out after the Tethered Satellite is retrieved Monday. A glovebox device on the middeck was set up and will be used later in the flight to conduct combustion experiments in an enclosed environment.

The astronauts also activated the Commercial Protein Crystal Growth experiment designed to grow nearly perfect crystals for study back on Earth for the possible development of better pharmaceuticals.

Columbia will remain in a near circular 160 nautical mile orbit for most of the mission, circling the Earth every 90 minutes to provide the crew with views of a sunrise and sunset 16 times each day.

On Friday, February 23, 1996, 6 a.m. CST, STS-75 Payload Status Report # 01 reports: (0/15:42 MET)

Mission Specialist Claude Nicollier, Payload Commander Franklin Chang-Diaz and Payload Specialist Umberto Guidoni started their duty shifts by activating the Shuttle Electrodynamic Tether System (SETS), the Deployer Core Equipment (DCORE), the Tethered Satellite System (TSS) carriers and the TSS deployer. The SETS investigation, by Dr. Brian Gilchrist of the University of Michigan, will study the electrical characteristics of the Tethered Satellite System and also will explore the use of space tethers as science tools. The Core experiment, by Dr. Carlo Bonifazi of the Italian Space Agency, will demonstrate the ability of a tethered system to produce electricity.

In addition to increasing understanding of physical processes in the near-Earth space environment, these studies will help provide explanations for events witnessed elsewhere in the solar system, such as the formation of comet tails and the bursts of radio "noise" detected from Jupiter. Tether science research will allow scientists to conduct unique, new types of electrical experiments and to develop new and promising tether applications in space technology.

Mission Specialist Jeffrey Hoffman then tested the Tethered Satellite System reel motor assembly and the Satellite restraint latches. These latches, which worked very well, will release the Tethered Satellite on Saturday, allowing the satellite to be reeled out to its maximum deployment of twelve miles (20.7 kilometers), making the Tethered Satellite-Shuttle system the longest electrically conductive object ever flown in space.

Nicollier and Chang-Diaz also checked out the Tether Optical Phenomena (TOP) experiment and the computers associated with deployment of the Tethered Satellite. The experiment, conducted by Dr. Stephen Mende of Lockheed Martin, will provide visual data that will aid scientists in answering a variety of questions concerning the Tethered Satellite's objectives during its flight in Earth orbit.

The Marshall-managed Tethered Satellite System Reflight (TSS- 1R) mission is a reflight of the Tethered Satellite System (TSS-1), which was flown on the Space Shuttle in July/August 1992. Building on the knowledge gained on the first Tethered Satellite mission about tether motions, the Tethered Satellite System will circle the Earth, placing the tether well within the electrically charged layer of the atmosphere known as the ionosphere. There, a satellite attached to Columbia by a thin conducting tether will be deployed into the ionosphere from the Shuttle payload bay, providing scientists with unique experimental opportunities.

The United States Microgravity Payload (USMP-3), also managed by the Marshall Space Flight Center, soon will have completed its first 24 hours in orbit, nestled safely within the confines of the Shuttle Columbia's cargo bay. Mission Specialist Maurizio Cheli activated the payload's support equipment, and Chang-Diaz turned on the experiments in the cargo bay.

Following the successful power-up of the experiments onboard, science teams located at Marshall's Spacelab Mission Operations Control Center began remotely monitoring and interacting with the Microgravity Payload. The USMP-3 experiments are designed to increase scientists' understanding of materials science and condensed matter physics. These experiments include the MEPHISTO directional solidification furnace, the Advanced Automated Directional Solidification Furnace (AADSF), the Isothermal Dendritic Growth Experiment (IDGE) and the Critical Fluid Light Scattering Experiment, or Zeno.

Working in Columbia's cabin, Chang-Diaz examined the Middeck Glovebox Facility while Nicollier activated the Commercial Protein Crystal Growth experiment. The glovebox, managed by the Marshall Space Flight Center, is a contained work area where crew members will conduct three combustion investigations that would be impractical and potentially hazardous if performed outside the glovebox in the open cabin environment. These experiments include the Forced-Flow Flamespreading Test and Comparative Soot Dynamics, developed by Kurt R. Sacksteder and Dr. David L. Urban, both of the Lewis Research Center, and the Radiative Ignition and Transition to Spread Investigation, developed by Dr. Takashi Kashiwagi of the National Institute for Standards and Testing. The Protein Crystal Growth investigation will process nine different proteins for the development of new therapeutic treatments for infections, human cancers, hormone disorders and Chagas disease.

On Friday, February 23, 1996, 4:30 p.m. CST, STS-75 MCC Status Report # 03 reports:

Although running into tethered satellite computer problems that remain under investigation by flight controllers and scientists, Columbia's crew pressed ahead this afternoon with checkouts and preparations for a Saturday deploy of the satellite.

The tethered satellite itself was powered up and appears to be in excellent condition. However, activation and checkout of the satellite-related experiments that are mounted in Columbia's cargo bay fell behind schedule when a computer relay for data and commands experienced problems. The Smart Flexible Multiplexer Demultiplexer (SFMDM), or "Smartflex", as the computer relay is called, was switched to a backup component after experiencing an apparent overload when some of the cargo bay experiments were first powered up.

The backup "Smartflex" equipment is working well, but controllers are evaluating its performance for several hours before attempting to repower the cargo bay-mounted satellite experiments and put further demands on the unit. At this point, there is still enough time prior to Saturday's planned 2:37 p.m. satellite deploy to reactivate those experiments and perform all needed checkouts and fine-tuning. Flight controllers currently plan to begin those procedures this evening aiming toward an on-time satellite flyaway.

In addition to the computer relay trouble, the crew reported apparent balky processing by an onboard laptop computer used as one method of displaying information from the satellite experiments. The Portable General Purpose Support Computer (PGSC) was switched for a backup laptop computer by the crew, and the data connections to the computer ports also were switched to backup ports. However, the apparent slow processing persisted. Flight controllers are evaluating the cause of the trouble, and any impact it may have on the planned operations.

The "Smartflex" must be operating for a deploy of the tethered satellite since it provides data and commands to the satellite-related experiments and equipment in the cargo bay. Communications and commanding of the satellite itself during deploy, however, is done by a radio link to Columbia.

On Friday, February 23, 1996, 6 p.m. CST, STS-75 Payload Status Report # 02 reports: (01/03:42 MET)

At the end of the first flight day, STS-75 crew members aboard the Space Shuttle Columbia were continuing predeployment checkout and activation of the Tethered Satellite System (TSS), a cooperative venture between NASA and the Italian Space Agency. The satellite, attached to the Shuttle by a pencil-thin tether, is being readied for deployment to a distance some 12.5 miles (20.7 kilometers) above the orbiter. This upward deployment, planned for Saturday afternoon, will begin a series of electrodynamic investigations using the Shuttle-tether-satellite system as it moves at 17,000 miles per hour through Earth's magnetic field lines to produce electrical current and voltage.

Crew members methodically stepped through detailed troubleshooting procedures for three of 18 TSS on-board computers. The smart flexible multiplexer/demultiplexer or relaying computer, called "smartflex," which sends crew commands to the tethered satellite and collects some science data, experienced timing errors, causing it to automatically switch over to its backup system. The backup system appears to be operating well and the timing errors of the smartflex computer are continuing to be investigated.

Payload Specialist Dr. Umberto Guidoni and Mission Specialist Jeff Hoffman changed out the Data Display and Control System (DDCS), a laptop computer that graphically displays TSS data, because it was operating at a low performance level. The backup computer was successfully booted, but readings showed that it also was operating sluggishly. Since the smartflex and DDCS computers are linked, flight controllers are checking to see if these problems may be related.

When activated, the data acquisition and control assembly computer that monitors various TSS parameters gave normal readings except for tether length. A reading of 76 feet (23 meters) was shown when it should have been zero. The system was later reset to zero and the computer responded correctly. This reading will be rechecked after the boom on which the satellite is mounted is extended in preparation for deployment.

Meanwhile, Payload Commander Franklin Chang-Diaz continued science activation procedures in an effort to keep the satellite deployment timeline on track. Science activities completed to this point include activation of the Shuttle Electrodynamic Tether System ion and electron sensors, as well as activation and checkout of the TSS Deployer Core Equipment and Satellite Core Equipment hardware, including the electron guns used to eject the tether current back into the ionosphere at the orbiter. Also, activation and checkout of the satellite and its three investigations were completed. These include: Research on Electrodynamic Tether Effects, which measures electric fields; Research on Orbital Plasma Electrodynamics, which measures ions and electrons; and Magnetic Field Experiment for TSS Missions, which measures magnetic fields. Baseline data were collected both about the charged particle environment of Columbia's cargo bay, as well as the effect of dynamic "noise" produced by activities such as thruster firings and water dumps to see how these vibrations are read by the satellite's sensors.

One of the unique features of this complex research flight is that the seven-member international crew is working in three staggered shifts instead of the normal two. This allows the crew to operate a suite of instruments designed to gather real-world information about how conducting tethers might be used to generate electrical power for spacecraft and to learn to control tethers in space. Ground-based researchers stationed at Spacelab Mission Operations Control also hope to validate theories that could lead to numerous future applications of tethers in space. Such possibilities range from positioning scientific research platforms downward into regions of Earth's atmosphere that are too high for science balloons and too low for remote sensing satellites, and to use the force created by current flow in a tether to reboost spacecraft as their orbit decays due to atmospheric drag, thereby saving fuel.

Another unique feature of the tethered satellite mission is that the science investigations all work together to give researchers an integrated picture of system performance and to characterize the charged particle environment in and around the Shuttle orbiter, which acts as an integral part of the overall tethered system. The tethered satellite is coated with an electrically conducting paint. The tether that secures it to Columbia's cargo bay has a copper core and is covered by Teflon and Kevlar, the material used in bullet- proof vests, to shield the tether from the harsh space environment. Scientific instruments are housed in the upper half of the satellite, and on the Mission Peculiar Equipment Support Structure that is attached to the Spacelab platform in the cargo bay. Three ground tracking stations located along the Shuttle's flight path will collect additional science data during the tether mission.

Meanwhile, data is being received by experiments that make up the third United States Microgravity Payload (USMP-3), awaiting its turn as the primary payload after TSS operations are completed. In fact, "the best images ever sent down" of dendrites were reported by Dr. Martin Glicksman, principal investigator of the Isothermal Dendritic Growth Experiment (IDGE). Dendrites are microscopic tree-like structures formed by molten materials as they solidify into the familiar materials used for everyday products ranging from aluminum cans to airplane turbine blades.

Overnight, crew members will continue activating and calibrating TSS systems and experiments, and making other preparations for tomorrow's satellite deployment and the beginning of 20 hours of science data collection.

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