PROGRAM TITLE: Earth Probes Program ACTIVITY STREAMS: Observations & Data Management SCIENCE ELEMENT:Climate and Hydrologic Systems Biogeochemical Dynamics Ecological Systems and Dynamics Solid Earth Processes Solar Influences NATIONAL AERONAUTICS AND SPACE ADMINISTRATION SCIENTIFIC MERIT: The centerpiece of NASA's contribution to understanding global climate change is the Earth Observing System (EOS) Program, a series of polar orbiting platforms for long-term global observations of the Earth's land, biosphere, atmosphere and oceans. The Earth Probes (EP) Program includes low-to-moderate cost missions designed to complement EOS by acquiring observations that require specific orbits and/or timeliness that cannot be met by the EOS Program. Earth Probes contribute to all U.S. Global Change Research Program (USGCRP) goals and objectives, and the scientific basis for the missions results from priorities and requirements of the scientific community, including recommendations of the National Academy of Sciences. As an ongoing series, the individual spacecraft and instruments will be implemented as the funding, scientific priorities, and readiness permit. Currently, the EP Program includes three missions: the Total Ozone Mapping Spectrometer (TOMS), the NASA Scatterometer (NSCAT), and the Tropical Rainfall Measuring Mission (TRMM). Each of these approved missions are part of international cooperative projects. The TOMS instrument missions (planned for 1994, 1996 and 1998) will continue the high-resolution global mapping of total stratospheric ozone which began in 1978 with the TOMS instrument on Nimbus-7 and followed in 1991 with the TOMS instrument on the Soviet Meteor-3 weather satellite. TOMS measurements are vital to the continuing effort to monitor and understand the dynamics of stratospheric ozone depletion. This is part of the research in biogeochemical dynamics, specifically changes in the atmospheric processes. Research using this data is directed to the detection of total ozone trends and to the verification of chemical models of the stratosphere used to predict future trends. The NSCAT instrument mission (planned for 1996) measures ocean surface wind velocity and provides data on air-sea interactions crucial to understanding oceanic uptake of carbon dioxide and other gases. NSCAT addresses fundamental processes in which the oceans and the atmosphere play a role in moderating the Earth's climate. Surface marine winds modulate the fluxes of momentum, heat, and moisture between the atmosphere and ocean. These fluxes drive both the atmospheric and oceanic circulations, and are critical to understanding and developing accurate coupled atmosphere/ocean circulation models needed for short- and long-range climate forecasting. NSCAT will contribute the single most important missing factor for advancing the understanding of wind-driven ocean circulation--the lack of systematic high-resolution wind observations over the ocean. The goal of the TRMM mission (planned for 1997) is to obtain a minimum of three years of climatologically significant observations of rainfall in the tropics. TRMM will play a significant role in global change studies, especially in developing an interdisciplinary understanding of atmospheric circulation, ocean-atmospheric coupling and tropical biology. General circulation models require detailed data on the latent heating of equatorial air masses, and the forcing and propagation speed of waves involved in the 30- to 60- day tropical oscillations. TRMM data on tropical clouds, evaporation, and heat transfer will be used to understand the larger scale coupling of the atmosphere to oceans, especially in the development of El Nino events, and in the more general understanding of ocean- atmosphere circulation. Tropical rainfall is also closely coupled to tropical forest processes. Convective mixing of trace gases, including carbon dioxide and methane, provides a direct link between tropical rainfall and the global biogeochemical cycles that regulate life on Earth. NASA's long range plans include additional Earth Probes addressing specific Earth science investigations. Several mission categories have been identified to provide critical Earth science measurements not provided by the international constellation of satellites. NASA intends to pursue collaborations with domestic and/or international partners in the following disciplines: gravity and magnetic fields, solid earth topography, and ocean topography. STAKEHOLDERS: TOMS will fly on a U.S.-launched free-flyer in 1994, on the Japanese ADEOS mission in 1996, and on an international mission of opportunity in 1998. The TOMS ozone data are of wide interest to a large international scientific community, and is coordinated with the UN Environmental Program (UNEP) and through the World Meteorology Organization (WMO) with participation by the National Oceanic and Atmospheric Administration (NOAA) and the Environmental Protection Agency (EPA) for global ozone change monitoring in accordance with the Montreal Protocol. NSCAT will also fly on the Japanese ADEOS mission in 1996, and the data will be a key contribution to major international ocean/atmosphere research programs, including the World Ocean Circulation Experiment (WOCE) and the Tropical Ocean Global Atmosphere (TOGA) program, both of which are components of the World Climate Research Program (WCRP). The TRMM mission in 1997 is a joint mission with Japan who will provide the launch vehicle and the Precipitation Radar instrument. There will also be broad international participation in the ground-based validation of the TRMM measurements. The Global Energy and Water Cycle Experiment (GEWEX), an initiative of the WCRP, will also employ and validate TRMM data. Other international programs, such as the International Geosphere-Biosphere Program (IGBP), will also use TRMM data for investigation of hydrologic processes important to global change. POLICY RELEVANCE: Primary - Climate Change and Global Warming - Stratospheric Ozone and UV-B Radiation Secondary - Ecological & Biodiversity - Seasonal and Interannual Prediction PROGRAM CONTACT:Lenwood G. Clark Office of Mission to Planet Earth NASA Headquarters, Code YF tel: 202-358-0786 fax: 202-358-2769 E-mail: L.CLARK.NASA/omnet