The Middle and Upper atmosphere (MU) radar is a large Doppler radar built for atmospheric observation at Shigaraki MU Observatory located at Shigaraki in the Shiga prefecture, Japan (34.86N, 136.11E, 385m MSL) in the middle latitude. The construction was completed in November 1984. The MU radar has a circular antenna array of 103 m in diameter, which consists of 475 three-element Yagis. It is an active phased array system with each Yagi driven by a solid-state transceiver module. This system configuration makes it possible to direct the antenna beam by electronic control up to 2500 times per second. The MU radar transmits an intense radio wave of 46.5 MHz to the sky and receives extremely weak echoes scattered back by atmospheric and ionospheric turbulences. It can observe winds and turbulence in the altitude range from 2 km to 500 km including the troposphere, stratosphere, mesosphere, thermosphere and ionosphere.