ATLAS 3 Public Affairs Status Report #12 6:00 a.m. CST, Nov. 9, 1994 MET 5/19:00 Spacelab Mission Operations Control Marshall Space Flight Center Huntsville, Ala. Halfway through the eleven-day ATLAS 3 mission, the atmospheric instruments continue to amass detailed information on the chemical constituents of the middle atmosphere. These instruments are working well and are providing high-quality data to the science teams. The solar instruments are in standby, as science teams evaluate data from the first two solar observation periods and prepare for the third. The Atmospheric Trace Molecule Spectroscopy (ATMOS) experiment measured the chemical and physical composition of the middle atmosphere. Since ATMOS first flew on Spacelab 3 in 1985, scientists have retrieved height profiles of over 30 trace gases from ATMOS data, including several chlorofluorocarbons, nitrogen-oxygen compounds, ozone, carbon monoxide, carbon dioxide, water and methane. The instrument measures these gases selectively and can simultaneously observe about ten to fifteen trace gases in one observation. The ATMOS instrument viewed the stratosphere at orbital sunrise and sunset, gathering information in the infrared portion of the electromagnetic spectrum. Since trace gas molecules absorb solar radiation at different wavelengths, ATMOS determines which wavelengths are being absorbed, giving scientists a more detailed picture of the molecular makeup of the atmosphere. ATMOS data from ATLAS 3 will be compared to information gathered during other missions to examine worldwide, seasonal and long-term atmospheric changes. According to Principal Investigator Mike Gunson, ATMOS has already far exceeded its minimum success requirements for the mission, performing "well beyond expectations" on its "most productive, and certainly most scientifically interesting, flight ever on any Shuttle mission." ATMOS has now filled about 80 percent of its onboard recorder, having completed a total of 166 sunrise and sunset observations. The Shuttle Solar Backscatter Ultraviolet (SSBUV) experiment continued to perform coincident measurements for NASA's Total Ozone Mapping Spectrometer (TOMS) and with ozone measuring instruments flying on the NOAA 9 satellite as called for by the National Plan for Stratospheric Monitoring. The SSBUV instrument makes its ozone measurements by comparing the amount of solar radiation reaching the top of the Earth's atmosphere to the amount being scattered back from the atmosphere. This information gives scientists a measure of the amount of ozone present in a given area. At around 3:45 CST this morning, the SSBUV team participated in what Principal Investigator Ernest Hilsenrath called "a spontaneous experiment collaboration" with the Middle Atmosphere High Resolution Spectrograph Investigation (MAHRSI) instrument to test the possibility of using MAHRSI's limb-scanning ability to measure ultraviolet radiation and ozone in the lower stratosphere. Taking advantage of a planned CRISTA-SPAS maneuver in which MAHRSI scanned the ultraviolet portion of the electromagnetic spectrum at heights between 55 and 15 km, the SSBUV team cooperated with the MAHRSI team to demonstrate the feasibility of this ozone limb-scanning technique in preparation for a solar limb- scanning instrument currently under development for possible use on future space missions. SSBUV measures ozone in the upper stratosphere by looking straight down at the Earth using ultraviolet backscatter observations. MAHRSI, on the other hand, measures hydroxyl and nitric oxide in the stratosphere and mesosphere, using limb-scanning, or edge on viewing above the Earth's horizon. This experiment successfully demonstrated the feasibility of using limb-scanning of the ultraviolet spectrum to obtain ozone measurements in the lower stratosphere. According to MAHRSI Principal Investigator Robert Conway, "there was a question about whether our instrument had enough sensitivity to perform this experiment successfully, but, sure enough, we did. The data look excellent." Analysis of this experiment's results will continue throughout the next shift. During the second half of the next 12 hour shift, the four solar science instruments for ATLAS 3 will begin their third period of solar observations. The Active Cavity Radiometer Irradiance Monitor, from the Jet Propulsion Laboratory, and Belgium's SOLCON experiment will measure the total solar energy received by the Earth. The SOLSPEC experiment will concentrate on the sun's radiant output in ultraviolet, visible and infrared wavelengths while the U.S. Naval Research Laboratory's Solar Ultraviolet Spectral Irradiance Monitor examines solar output in the ultraviolet wavelengths. SSBUV will also observe the sun during one or two of the solar orbits, and the second Experiment of the Sun for Complementing the Atlas Payload and for Education (ESCAPE-II) will be in operation for all solar orbits.