High Quality Content by WIKIPEDIA articles! The UDOP (UHF Doppler) multistatic radar and multiradar system (MSRS) utilizes Doppler radar for missile tracking and trajectory measurement. A target is illuminated at 450 MHz. Five receiving stations, located along the baselines with the lengths from 40 to 120 km (25 to 75 mi), receive signals from the target`s transponder at 900 MHz. These five stations yield slant-range rate. To compute the range or position, an initial position is required from some other tracking system. The random error is 6 cm (2.4 in), but total error includes the systematic error of 2.7 m (8.9 ft) plus the initial error. UDOP had relatively low cost compared with other high-accuracy systems. In the US, MSRS has found important application in the precision measurement of missile trajectories at the Air Force Eastern Test Range, which extends from the Florida mainland to the Indian Ocean. These MSRSs include the AZUSA, the MISTRAM, and the UDOP. All systems employ a cooperative beacon transponder on the observed target and a ground-based transmitting station with several receiving stations at separate, precisely located sites.