ATLAS 3 Public Affairs Status Report #3 6:00 p.m. CST, Nov. 4, 1994 MET 1/7:00 Spacelab Mission Operations Control Marshall Space Flight Center Huntsville, Ala. With the STS-66 mission well into its second day in orbit, six additional instruments are at work to decipher the complex chemistry of Earth's atmosphere. The flight is part of NASA's Mission to Planet Earth, a coordinated research effort to comprehensively study the planet's environment. The mission's first solar observation period, which began around noon today, will measure the sun's energy during daylight portions of eight orbits. All four solar instruments are veterans of both previous ATLAS flights, plus either Spacelab 1 or 2 in the mid-1980s. The Jet Propulsion Laboratory's Active Cavity Radiometer Irradiance Monitor (ACRIM) and Belgium's Measurement of the Solar Constant (SOLCON) experiment detect the total amount of radiation from the sun, to within 0.1 percent accuracy. The Solar Spectrum Measurement (SOLSPEC) experiment from France breaks sunlight down into ultraviolet, visible and infrared wavelengths, while the Naval Research Laboratory's Solar Ultraviolet Spectral Irradiance Monitor (SUSIM) concentrates on ultraviolet radiation. Sunlight, particularly ultraviolet radiation, provides energy for the chemical reactions that create atmospheric changes. Before scientists can predict accurately how human activity will affect the atmosphere, they must thoroughly understand the natural forces driving it. Even small fluctuations in solar radiation are important parts of that equation. For instance, variations of one percent or less in total solar radiation could cause droughts or lengthy periods of unseasonal cooling. Two new atmospheric instruments are in operation for the first time in space - the Cryogenic Infrared Spectrometers and Telescopes for the Atmosphere (CRISTA) experiment and the Middle Atmosphere High Resolution Spectrograph Investigation (MAHRSI). Both are aboard the autonomous CRISTA-SPAS satellite, which the crew deployed at 6:50 CST this morning. After receiving several hours of start-up commands from the operations team at Kennedy Space Center, the instruments made their first observations shortly before noon. CRISTA, provided by the University of Wuppertal in Germany, is gathering data to give scientists their first three-dimensional global "maps" of the middle atmosphere. The instrument uses three infrared telescopes looking in different directions to locate small-scale structures of various gases, thought to be distributed in the atmosphere by winds, wave interactions, turbulence and other disturbances. Global measurements of these gases and their changes will help scientists create more precise models of the chemistry and dynamics of the stratosphere - the region of the atmosphere 10 to 30 miles above the Earth which contains the ozone layer - and give them a better understanding of Earth's energy balance. Science operations for CRISTA were interrupted when the satellite's guidance system lost sight of its reference stars this afternoon, but they resumed when ground commands successfully reoriented the satellite a few hours later. MAHRSI is making ultraviolet measurements of nitric oxide and hydroxyl in an area parallel to that of CRISTA's center telescope. Comparing results from CRISTA and MAHRSI will provide important insights into the chemistry and the heating and cooling of the middle atmosphere. Both hydroxyl and nitric oxide are natural chemicals that react with ozone and other gases to affect the chemical balance of the ozone layer. This is the first time hydroxyl has been measured from space so low in the atmosphere. Principal Investigator Dr. Robert Conway, of the Naval Research Laboratory in Washington, D.C., reports that the first data received from MAHRSI is remarkably close to their predictions, based on expected hydroxyl amounts and instrument properties. While the CRISTA/SPAS instruments were being activated, the Atmospheric Trace Molecule Spectroscopy (ATMOS) experiment got two bonus observations of orbital sunsets, measuring the distribution of trace gases in the atmosphere over northern Europe. This morning, the Goddard Space Flight Center's Shuttle Solar Backscatter Ultraviolet (SSBUV) experiment completed internal calibration exercises to ensure it is operating properly. The experiment team is completing preparations for SSBUV to take its first science data - measurements of ultraviolet radiation from the sun - on the last two solar orbits tonight. This afternoon, Payload Commander Ellen Ochoa restarted the ATLAS 3 Global Positioning System (GPS), and it locked onto four of the positioning satellites in orbit. An earlier attempt had only locked onto two of the necessary four satellites. This will give ATLAS 3 experiment teams an extra means for verifying the precise locations where their instruments take data. Primary position information comes from the Shuttle's inertial measurement units. ATLAS 3 payload controllers and the Millimeter Wave Atmospheric Sounder (MAS) team in Huntsville are investigating a loss of science data transmission from the MAS instrument, which occurred after its successful observations last night. Thus far, they have not determined the source of the problem. The next MAS operations are scheduled for early tomorrow morning. After solar observations conclude just before midnight, the crew will point the Shuttle toward the CRISTA-SPAS satellite to receive a sample of science data to be relayed to the ground. Then the atmospheric instruments will begin another set of measurements, and SSUBV will make its first ATLAS 3 readings of global ozone.