An upgraded version of the Indian MST radar, called Advanced Indian Mesosphere-Stratosphere-Troposphere (MST) radar (AIR), has recently been commissioned. The prime objective of constructing the AIR is to make it a more useful instrument for conducting new experiments, which enable us to broaden our knowledge on the dynamical and electrodynamical processes including coupling from the boundary layer to the ionosphere. The AIR works at 53 MHz, and the system has been rebuilt, keeping the original square antenna array consisting of 1,024 Yagi antennae. The AIR is a high-power, fully active phased array system with dedicated 1-kW solid-state transmit-receive units, providing a total peak power of 1,024 kW, and control systems that allow steering the beam with 360°azimuth and 24°zenith agility. Also, the antenna system has been configured with modularity and scalability, which facilitates selection of antenna subarray and aperture for carrying out multireceiver experiments. The antenna radiation pattern tests reveal that the beam width and first side lobe level are close to the designed values of 2.2°and −13.2 dB, respectively. Currently, the system is equipped with 18 receivers to carry out spaced receiver experiments. The transmitters have been designed to transmit very short and long pulses for studying boundary layer to ionosphere. This paper presents the system description of the AIR and sample observations made using the system in Doppler beam swinging mode demonstrating its capabilities for studying neutral atmosphere and ionosphere.

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