This paper reports on a new satellite sensor, the Geostationary Earth Radiation Budget (GERB) experiment. GERB is designed to make the first measurements of the Earth's radiation budget from geostationary orbit. Measurements at high absolute accuracy of the reflected sunlight from the Earth, and the thermal radiation emitted by the Earth are made every 15 min, with a spatial resolution at the subsatellite point of 44.6 km (north–south) by 39.3 km (east–west). With knowledge of the incoming solar constant, this gives the primary forcing and response components of the top-of-atmosphere radiation. The first GERB instrument is an instrument of opportunity on Meteosat-8, a new spin-stabilized spacecraft platform also carrying the Spinning Enhanced Visible and Infrared (SEVIRI) sensor, which is currently positioned over the equator at 3.5°W. This overview of the project includes a description of the instrument design and its preflight and in-flight calibration. An evaluation of the instrument performance after its first year in orbit, including comparisons with data from the Clouds and the Earth's Radiant Energy System (CERES) satellite sensors and with output from numerical models, are also presented. After a brief summary of the data processing system and data products, some of the scientific studies that are being undertaken using these early data are described. This marks the beginning of a decade or more of observations from GERB, as subsequent models will fly on each of the four Meteosat Second Generation satellites.
Blackett Laboratory, Imperial College, London, United Kingdom
Rutherford Appleton Laboratory, Oxfordshire, United Kingdom
Royal Meteorological Institute, Brussels, Belgium
University of Leicester, Leicester, United Kingdom
National Institute of Aerospace, Hampton, Virginia
Science Applications International Corporation, Hampton, Virginia
Environmental Systems Science Centre, University of Reading, Reading, United Kingdom
Hadley Centre for Climate Prediction and Research, Met Office, Exeter, United Kingdom
CURRENT AFFILIATIONS:*Analytical Services and Materials, Inc., Hampton, Virginia
+Surface Measurement Systems Ltd., London, United Kingdom
#EUMETSAT, Darmstadt, Germany
@Center for Space Research, Massachusetts Institute of Technology, Cambridge, Massachusetts
