Gadanki Ionospheric Radar Interferometer (GIRI) established at NARL
National Atmospheric Research Laboratory (NARL) at Gadanki, an autonomous research institute of Department of Space, is engaged in fundamental and applied research in the field of Atmospheric Sciences. A new 30 MHz radar system, Gadanki Ionospheric Radar Interfereometer (GIRI), has been established at NARL for ionospheric, meteor and space weather research in a comprehensive way. GIRI consists of a rectangular antenna array of 160 two-element Yagi-antenna arranged in a 20×8 matrix, twenty transmitter units providing a maximum peak power of 160 kW, six digital receivers including data processing systems, a radar controller, and a host computer.
GIRI has been designed with the following objectives:
– to carry out unattended observations towards studying the forcing from the sun (e.g., variation in solar flux, solar flare, magnetic storm) and from the underneath atmosphere (e.g., waves generated by weather phenomena) on the ionospheric irregularities
– to steer the radar beam on a pulse-to-pulse basis up to ±50o in the east-west plane providing spatial map of ionospheric irregularities covering about 10o longitude belt around Gadanki, to study evolution of irregularities
– to measure Doppler velocity unambiguously by taking advantage of the wavelength (10 m) and also by double-pulse technique to study polarisation processes and supersonic plasma flow
– to measure Doppler spectrum of overspread targets with a-periodic pulsing scheme to study different regimes of electrostatic turbulence
– to measure zonal drift of irregularities using interferometry technique
– to perform in-beam interferometric imaging of small scale structures and their dynamics.
The beam agility would provide important information on the angular location of plasma irregularities during the onset phase and its relationship to background ionospheric state parameters and sunset terminator. Investigations made using the new capabilities are expected to improve the skill in Equatorial Plasma Bubble (EPB) forecasting, as EPB is detrimental for satellite based navigation/communication applications.
Measurements made using GIRI and other ionospheric measurements using co-located radio and optical instruments along with the lower atmospheric measurements are being used by a large number of instrumental facilities which provides a unique opportunity to investigate the vertical coupling in a comprehensive way.
The proposed up-gradation of the upcoming active array MST radar into Incoherent Scatter Radar (ISR) will add a new dimension to the atmospheric and ionospheric research in the country. With the ISR upgrade, NARL will become the first comprehensive low latitude observatory in the world, providing a unique opportunity for scientists from both home and abroad to conduct frontline atmospheric and ionospheric research.
