The Precise RAnge and Range-Rate Equipment (PRARE) (more info here) is a highly accurate microwave ranging system aboard the European Remote Sensing Satellites ERS-1 (more info here and here) and ERS-2 (more info here and here). The applications of PRARE are: * precise satellite orbit determination (e.g. of altimeter and geodynamic satellites) * earth gravity fieldrecovery * precise point positioning (tectonics) * earth rotationparameter determination and measurement of the ionospheric totalelectron content (TEC)