Gravity field determination with GOCE and GRACE

The Gravity field and steady-state Ocean Circulation Explorer (GOCE) and Gravity Recovery And Climate Experiment (GRACE) are two gravity missions defined by the European Space Agency (ESA) and the National Aeronautics & Space Administration (NASA), respectively. The primary mission objective of GOCE is a high-accuracy, high-resolution determination of the constant part of the gravity field of the Earth, down to wavelengths of less than 200 km, whereas the GRACE mission aims at wavelengths down to 400 km and also focuses on monitoring changes in the Earth's gravity field. The foreseen mission duration is equal to 9 months for GOCE and 5 years for GRACE, respectively. With these mission durations, rigorous covariance analyses indicate that the gravity signal to noise ratio reaches I at about degree 250 for GOCE and 130 for GRACE, i.e. wavelengths of about 160 and 310 km, respectively. The covariance analyses indicate that GRACE and GOCE perform best in the long-to-medium wavelength (800 - 40,000 km) and medium-to-short wavelength (1500 - 160 km) domains, respectively. The GRACE and GOCE missions can be considered to be both supplementary and complementary. This offers the possibility to verify and calibrate gravity field recovery results, especially in the medium-wavelength domain. Moreover, a combined GOCE/GRACE gravity field solution might be formed, with optimal performance over all wavelengths down to 180 km. (C) 1999 COSPAR. Published by Elsevier Science Ltd.