The GRACE mission is a joint German-American project. The primary objective of the GRACE mission was to obtain accurate global models for the mean and time variable components of the earth´s gravity field. This goal was achieved by measurements of the inter-satellite range between 2 co-planar, low altitude near-polar orbiting satellites. In addition, each satellite carried a high accuracy accelerometer and a geodetic qualified GPS receiver to perform precise orbit determination, recover gravity data and to estimate the gravity field. The secondary task of the GRACE mission was to keep a daily record of several hundred globally distributed profiles of the delay or inclination angle of GPS measurements. Both can be converted into a total electron or refractivity by applying Atmospheric- and Ionospheric-Profiling. The German Space Operations Center configured the Ground Operations System and prepared and executed the GRACE mission operations.
Further information about GRACE can be found on the homepage of the University of Texas at Austin