1994 was the busiest year ever for atmospheric science observations from the Space Shuttle, with five of the eight shuttle flights having atmospheric science measurements as their primary or strong secondary goals. This flurry of activity marks the beginning of a transition period to a new era, however, as current plans for NASA's Mission to Planet Earth (MTPE) call for significantly reduced use of the Space Shuttle for atmospheric science measurements in the future. Furthermore, reduced budgets and a very busy Shuttle manifest place strong constraints on possible implementation of expanded use of the Space Shuttle by MTPE for atmospheric science measurements in the coming years.

To help assess the results from atmospherically-oriented Shuttle missions in the past few years and to provide recommendations to MTPE management concerning possible future use of the Space Shuttle for atmospheric science, a meeting on "Atmospheric Science Observations from the Space Shuttle" was held March 21-23 in Washington, DC. This article provides a summary of the motivation behind, and outcome of, this meeting.

Some fifty scientists from the U.S., France, Germany, and Belgium participated in the meeting. Participation at the meeting was invited from a broad cross- section of the atmospheric science community, including many principal investigators (PIs) and co-investigators associated with atmospheric science instruments and modeling efforts associated with the EOS program, as well as members of MTPE's Earth System Science and Applications Advisory Committee (ESSAAC).

The specific goals of the meeting were threefold. First, results of atmospherically-oriented observations were presented by principal investigators associated with the instruments that have flown aboard the Space Shuttle this past year. Second, a "customer assessment" was obtained from scientists associated with measurement and modeling programs that make use of data from the Shuttle-borne instruments. Third, scientists with interests in using the Space Shuttle as a platform for additional flights of existing instruments, or for initial flights of modified or new instruments, presented their wishes.

Among several questions which were asked of speakers at the meeting were how instrument development efforts and measurements obtained from Shuttle-borne instruments would feed into the EOS program. A particular question was what role Shuttle-based instruments could play in bridging gaps between currently operating and planned EOS instruments. Another focus was how results of Shuttle-based instruments could help in providing calibration information for satellite-based instruments.

The measurement programs for which results were presented at the meeting include the Measurement of Air Pollution from Satellites (MAPS) instrument (Vickie Connors, NASA/LaRC, PI), which flew twice on the Space Shuttle in 1994 as part of the Space Radar Laboratory (SRL) missions, the Lidar-in-Space Technology Experiment (LITE) instrument (M. P. McCormick, NASA/LaRC, PI), the third Atmospheric Laboratory for Applications and Science (ATLAS-3) payload (Timothy Miller, NASA/MSFC, Mission Scientist), the Shuttle Backscatter UltraViolet (SSBUV) instrument (Ernest Hilsenrath, NASA/GSFC, PI), which, like MAPS, flew twice in 1994 (once as part of a microgravity mission and once together with ATLAS-3) and the joint German/U.S. Cryogenic Infrared Spectrometers and Telescopes for the Atmosphere/ Shuttle Pallet Satellite (CRISTA/SPAS) payload (Dirk Offermann, Univ. Wuppertal, CRISTA instrument PI). Results from each of these programs were presented, although in many cases data were very preliminary.

Where individual programs included several instruments, scientists associated with each instrument made presentations. This included the ATLAS-3 payload, which consisted of six instruments, and the CRISTA/SPAS, which contained both the German CRISTA and the American Middle Atmosphere High Resolution Spectrographic Investigation, or MAHRSI instrument, with Robert Conway of the U.S. Naval Research Laboratory (NRL) as PI. For ATLAS-3 this included Michael Gunson, Jet Propulsion Laboratory (JPL), for the Atmospheric Trace Molecule Spectroscopy (ATMOS) instrument, Richard Bevilacqua from NRL for the joint German-Swiss-U.S. Millimeter-Wave Atmospheric Sounder (MAS) instrument, Michael VanHoosier, also of NRL for the Solar Ultraviolet Spectral Irradiance Monitor (SUSIM) instrument, Gerard Thullier of CNRS, France for the Measurement of the Solar Spectrum from 180 to 3200 nm (SOLSPEC) instrument, Richard Willson of JPL for the Active Cavity Radiometer Irradiance Monitor (ACRIM), and Dominique Crommelynck of the Royal Belgian Institute of Meteorology for the Measurement of the Solar Constant (SOLCON) instrument. Timothy Miller made a presentation on behalf of the Colorado Space Grant Consortium's Experiment of the Sun Complementing the ATLAS Payload and Education (ESCAPE II) instrument, which co-manifested with the ATLAS-3.

Measurement and modeling programs that gave "customer assessments" on the usefulness of Shuttle data included the Upper Atmosphere Research Satellite (Mark Schoeberl, NASA/GSFC, project scientist), the NASA/NOAA Solar Backscatter Ultraviolet (SBUV/2) program (Walter Planet, NOAA), the NASA Total Ozone Mapping Spectrometer (TOMS) program (P. K. Bhartia, NASA/GSFC, project scientist), the recently inaugurated Stratospheric Tracers of Atmospheric Transport (STRAT) aircraft campaign (Paul Newman, NASA/GSFC, project scientist), and assessment modeling efforts (Malcolm Ko, Atmospheric and Environmental Research, Inc. and Ross Salawitch, JPL). Particular attention was given to the role of the ATLAS payload relative to UARS, as a primary goal of the ATLAS series was to obtain coincident measurements with UARS, for which there are instruments which are either similar in objectives and technique, or in some cases, nearly identical (ACRIM and SUSIM instruments are on both UARS and the ATLAS payload). Additionally, the role of SSBUV in providing calibration information for the SBUV/2 instruments was a focus, as the SSBUV program was explicitly designed to help maintain calibration of the SBUV/2 instruments.

The final round of formal presentations at the meeting included ideas for future Shuttle instruments and reflights of existing instruments. These included ideas for continued flights of the ATLAS, SSBUV, CRISTA, and LITE payloads (with special mention of the need for an ATLAS flight in the late 1995-96 timeframe to help capture solar data during the time of the solar minimum‹Guenther Brueckner of NRL presented this), as well as ideas for several modified or new instruments. Dominique Crommelynck discussed the possibility of flying a modified version of the SOLCON instrument independent of ATLAS. Philip Schwartz of NRL discussed the possibility of modifications to the MAS instrument to measure ClO and HCl simultaneously through addition of channels in the 600 GHz region. Kelly Chance of the Harvard-Smithsonian Center for Astrophysics discussed a concept for the OH Interferometric Observation (OHIO) instrument, which is being designed as a balloon instrument but could be adapted for the Space Shuttle. Herbert Pickett of JPL discussed a possible Shuttle-based heterodyne OH instrument, which could provide a test of 2500 GHz band detection of space-based OH. Richard McPeters of NASA/GSFC discussed plans for the Shuttle Ozone Limb Sounder Experiment (SOLSE), which is currently under development at GSFC for a possible flight as a Get Away Special or Hitchhiker payload.

Possible constraints on Shuttle use associated with the manifest were discussed by Lou Caudill of MTPE's Flight Systems Division, while Mark Sistille of NASA's Office of Life and Microgravity Science and Applications discussed accommodations for science instruments which will be available on the International Space Station.

There was a half day of discussion at the meeting in three subgroups‹Solar Science (G. Brueckner, NRL, subgroup leader), New Science Opportunities from the Shuttle (Mark Zahniser, Aerodyne Research, Inc., subgroup leader), and Additional Science Opportunities using Existing Instruments ( Jae Park, LaRC, subgroup leader). The outcomes of the subgroup deliberations were presented to the full group in the final morning of the meeting. Based on the presentations made at the meeting, MTPE management is considering its options for use of the Space Shuttle.

Readers desiring further information about the meeting should contact the author, who served as organizer of this meeting. Contact may be made electronically (see above e-mail address), by phone at 202-358-0757, or by fax at 202-358-2770.

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