What is "udop"

The UDOP (UHF Doppler) multistatic radar and multiradar system (MSRS) utilizes Doppler radar for missile tracking and trajectory measurement. A target is illuminated at 450MHz. Five receiving stations, located along the baselines with the lengths from , receive signals from the target's transponder at 900MHz. 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 , but total error includes the systematic error of 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.

The UDOP used an AN/DRN-11 transponder installed in the Saturn (rocket family) launch vehicle for Project Gemini missions.

The C-band CW interferometric AZUSA, in operation from the 1950s, has one transmitter and nine receivers located along two crossed baselines with the total lengths of about . Intermediate receivers spaced at are used for phase ambiguity resolution. The AZUSA system measures range by phase measurement of sideband frequencies modulating the carrier, coherent range by Doppler count, two direction cosines, and two cosine rates. Errors of less than in range and 20 ppm in direction cosine are obtainable.

Missile Trajectory Measurement (MISTRAM) is a CW interferometric system with receiving stations situated along two mutually perpendicular baselines spaced at . This MSRS can measure range, four range differences, range rate and four range difference rates of a target. The range error is less than .