National Atmospheric Research Laboratory (NARL), an autonomous research institute of Department of Space is engaged in fundamental and applied research in the field of Atmospheric Sciences. A high power 53 MHz Mesosphere-Stratosphere-Troposphere (MST) Radar was established in 1992 as a national facility for atmospheric research. The MST Radar is a state-of-the-art instrument capable of providing estimates of atmospheric parameters with very high resolution on a continuous basis. It is an important research tool in the investigation of prevailing winds, waves (including gravity waves) turbulence, and atmospheric stability & other meso-scale phenomena. This radar is the second largest powerful radar in the world; the largest one is the 50 MHz Jicamarca radar, located in Lima, Peru.

NARL radar consists of 32 vacuum tube based transmitters providing a total peak power of 2.5 MW and a semi active antenna array of 1024 Yagi having aperture of ~1.7x104 m2 and was designed to study winds, waves and turbulence in the troposphere, stratosphere and mesosphere, and plasma irregularities and electrodynamics in the ionosphere. This radar has been extensively used for studying tropical atmospheric dynamics including short and long term wind variabilities with application to satellite launch missions and developing model, understanding plasma irregularities linked with equatorial plasma bubble for satellite-based communication/navigation applications, and understanding convective and precipitation systems.

An up-gradation project has been taken up to replace the tube based transmitters and semi-active antenna array with 1024 solid-state 1-kW Transmit-Receive (TR) modules each feeding one Yagi antenna making the radar system fully active with antenna beam agility covering 360o azimuth, which does not exist in the original system. Most importantly, this will allow conducting multi-receiver experiments for Spaced Antenna and Radar Interferometry/Imaging analysis of atmospheric echoes for in-beam imaging of refractive index field and winds. The up-gradation has been taken up without hampering the routine observational schedule catering to the scientific needs including the radar applications for rocket launch and weather modeling. One of the challenging tasks was to employ highly distributed underground power, RF and optical networks in the antenna array field required for all the 1024 TR modules for various purposes. This task has been completed successfully without affecting the important observational and maintenance schedules of the existing system.

The Figure shows the antenna field after execution of the underground networks and an on-field housing of four-TR modules for a 2x2 sub-array (inset). All TR modules along with other subsystems are expected to be fully integrated by the end of December 2015 for an overall test and evaluation.

With this upgradation, MST radar will become one of the powerful and versatile atmospheric radars in the world, which will offer opportunities for scientists from both home and abroad to conduct frontline research in atmospheric sciences.