Special operations of CERES for radiation experiment tests (SOCRATES) for Earth-based campaigns

The Clouds and Earth Radiant Energy System project flew a scanning radiometer aboard the Tropical Rainfall Measuring Mission TRMM satellite and two each aboard the Terra and Aqua spacecraft. The primary objectives of the pairs of instruments were for one to scan cross-track to map the geographical distribution of reflected solar radiation and Earth-emitted radiation and for the other to scan in azimuth as well as in nadir angle to provide data from which to develop models to describe the directionally-dependent distribution of reflected solar radiance and Earth-emitted radiance. This set of biaxially-scanning data contained 8000 days of measurements. These data were used with radiation transfer codes which had progressed during the fifteen years since the earlier ERBE models of anisotropy had been developed using 218 days of measurements from the Earth Radiation Budget instrument which flew aboard the Nimbus 7 spacecraft. The CERES radiation anisotropy models are major improvement over the earlier models. In addition to biaxially scanning to collect data for anisotropy models, the CERES instruments can be programmed for a wide variety of purposes. This capability was used to make measurements to compare CERES measurements with other radiation budget instruments: other CERES radiometers, ScaRaB 2 and GERB. In addition, special operations of CERES have been used to support Earth-based campaigns for which radiation budget is a major consideration. These campaigns include sites at the Chesapeake Bay, ARMS at the Southern Great Plains site in Oklahoma, the Anchor Station in Valencia, Spain, Point Barrow, Beijing during the Olympics, Niamey, Point Barrow and Princess Elizabeth Island. The University of Valencia operates a ground station in an agricultural area in Valencia, Spain. This station is at a European location at low latitude and nearly on the Prime Meridian, and thus provides a low view zenith angle for validation of instruments aboard the MeteoSat spacecraft. The station has a complete suite of meteorological instruments and radiometers for measuring solar and atmospheric radiation fluxes at the surface. During special campaigns balloon-sondes are released. In order to provide validation data, a CERES instrument was programmed to rotate such that during an overpass of the Valencia station, each scan went over the station. The radiances measured by CERES were then compared with the measurements from the ground radiometers by use of a radiation transfer code to take into account the atmospheric effects. The fluxes computed in this manner are presented and compared with the station radiometer measurements. In support of African Multidisciplinary Monsoon Analysis (AMMA), a mobile ARM station was set up at Niamey, Nigeria to measure surface radiation. This site is of interest because of the sand storms in the area. Several steps were taken in order to reduce the air pollution in Beijing during the Olympics. CERES was operated so as to scan over Beijing with each scan during fly-overs during this time in order to measure the radiation effects of decreasing the aerosols. These applications demonstrate the power of the programmable feature of the CERES instrument to operate with ground stations and other satellite instruments to generate data sets for various scientific investigations.