The gravity field of the Earth is variable in both space and time, and is an integral constraint on the mean and time variable mass distribution in the Earth. The science data from GRACE mission will be used to estimate global models for the mean and time variable Earth gravity field approximately every 30 days for the 5 year lifetime of the mission. The science data from GRACE mission consists of the inter-satellite range change measurements, and the accelerometer, GPS and attitude measurements from each satellite.

The GRACE flight configuration is shown above.