TSS-1R/USMP-3 Public Affairs Status Report #04 6:00 p.m. CST, Feb. 24, 1996 02/03:42 MET Spacelab Mission Operations Control Marshall Space Flight Center With the decision to delay deployment of the joint NASA/Italian Space Agency Tethered Satellite System (TSS) by one day, researchers located at Spacelab Mission Operations Control are working around the clock, analyzing initial data and ensuring that their instruments are ready for full-up science operations. The initiation of satellite deployment, known as "flyaway," now is scheduled for around 2:45 p.m. CST Sunday. TSS principal investigators and their science teams view this adjustment of the mission timeline as an opportunity to accomplish all their major science objectives. Specifically, Mission Scientist Nobie Stone, of the Marshall Space Flight Center (MSFC), pointed out that important baseline data collection would have been sacrificed by the rush to complete instrument activation and checkout if the satellite deployment had not been postponed by 24 hours. Dr. Stone emphasized that gathering baseline measurements before deployment is "like learning to walk before you run." Part of this data set reveals how the sensitive TSS scientific instruments react to periodic thruster firings to maneuver the Shuttle and the satellite. Today's science activities included mapping Earth's charged particle upper atmosphere, which varies dramatically as Columbia orbits through periods of daylight and darkness every 45 minutes. Scientists will use these and other predeployment background readings when they analyze data collected during the more than 30 hours of planned TSS science operations. One example of baseline data is the Joint Science Display produced earlier today by combining measurements gathered by several TSS instruments. This graphical profile of the intensity of charged particles around the Shuttle is giving scientists an indication of how instruments may respond when the tethered satellite collects such particles when deployed. This display showed intense electron and ion collection in the Shuttle's flight direction, or "ram," versus the trailing side, known as the "wake" direction. Another example of baseline data is a "space weather map" produced today by the Theory and Modeling Support of Tether (TMST) Sundial investigation. The map provides a global view of the plasma density and temperature in the ionosphere at the altitude of the STS-75 orbit (160 nautical miles). This map is produced from a combination of theoretical ionospheric models and measurements obtained from 30 ground-based stations around the world. Mission Manager Robert McBrayer, also of MSFC, said the deployment delay "makes sense," especially since the satellite will be operating on battery power once the umbilical that attaches it to the Shuttle's power system is removed shortly before flyaway. He emphasized the satellite and its deployer, as well as the TSS experiments, have been activated and are operating properly. McBrayer noted that ground- based flight controllers are using the extra time to better understand problems that arose and to develop enhanced contingency plans for satellite deployment. Essentially turning back the clock 24 hours, the crew spent the day stepping through normal science and satellite predeployment activities that were interrupted yesterday while they performed troubleshooting for three on-board computers. As part of a dress rehearsal for satellite deployment, the crew maneuvered Columbia to the altitude for satellite flyaway. They also worked through a number of steps designed to simulate the same orbital conditions and environment for actual deployment the satellite, including lighting and lighting angles. During some nighttime orbital passes, crew members worked with the Tether Optical Phenomena Experiment (TOP), which gave a stunning view of atmospheric air glow and auroras over the South Pole as viewed from the flight deck's overhead window. This is the window through which the crew later will watch the deployed satellite. TOP science team members viewed live video images and sent voice commands to vary the filters and exposure setting for better viewing. The heart of the TOP instrument is a hand-held low-light video camera with special filters whose primary purpose on TSS is to observe luminescence produced by electron beams and the interaction of the electrically charged satellite with the local charged-particle and neutral atmosphere. The TOP has many advantages over similar photographic recordings made on previous flights because it allows real-time observations of the images seen by the orbiter crew. The crew also resumed calibration of on-board instruments and electron accelerators, including one test of the Shuttle Electrodynamic Tether System (SETS). SETS instruments, mounted in the cargo bay, will make measurements of tether voltage and current, as well as background magnetic fields and plasma characteristics. SETS also provides one electron accelerator, known as an electron gun, designed to propel charged particles back into the ionosphere after they travel from the satellite, down the conducting tether, and collect in the cargo bay. The ejection of electrons is one step in completing the circuit required for current to flow. During the next 12 hours, science data will continue to be collected while the crew continues predeployment activities. Status reports are issued from Marshall Space Flight CenterŐs Spacelab Mission Operations Control at 6 a.m. and 6 p.m. weekdays, and at 6 a.m. on weekends; and from Johnson Space Center's Mission Control at 8 a.m. and 5 p.m. For additional information, see the USMP-3 payload Internet homepage at http://liftoff.msfc.nasa.gov/sts-75/usmp-3/usmp-3.html, the TSS-1R payload Internet homepage at http://liftoff.msfc.nasa.gov/sts-75/tss- 1r/tss-1r.html and the STS-75 Shuttle Mission Internet homepage at http://www.ksc.nasa.gov/ shuttle/missions/sts-75/mission-sts-75.html.