A supersensitive accelerometer for spacecraft gradiometry

An exact knowledge of the earth's gravity field is needed for advanced studies related to solid earth and ocean physics. A study (GRAVSAT-A) is currently considered by NASA to determine the gravity field with an accuracy of 2-3 mgal change and a resolution of 100 km using satellite to satellite range rate tracking techniques. The present investigation has the objective to prepare the foundation of an advanced GRAVSAT-B mission in the 1990s with an accuracy of about 1 mgal and a resolution of about 50 km. It is possible that satellite to satellite tracking will not be able to satisfy these requirements. However, it appears that a new technology, called "high sensitivity gradient gradiometry", could be employed to achieve the aims of the GRAVSAT-B mission. Attention is given to a new type of gravity gradiometer using superconducting microwave cavity oscillator accelerometers.