The Precise Range And Range-Rate Equipment (PRARE) : was a microwave tracking system on board the ERS-1 mission. It operated at centimetre accuracy levels for the measurement of satellite to ground range and range rate. The concept was based on an autonomous spaceborne two-way and dual frequency microwave tracking system with its own telemetry, telecommand, data storage, timing and data transmission capabilities. This allowed data analysis on a global basis within a very short time delay. Due to the microwave transmission concept, the system operated independently from weather and daylight conditions.