VHF Radars

The radar back-scattering coherent 50 MHz (RESCO) that was installed in São Luís Space Observatory / INPE, whose operation was started in August 1998, is able to perform measurements of the plasma dynamics of the electrojet and equatorial ionospheric bubbles . This radar was designed to map the electromagnetic drift turbulence and irregularities of the short length scale (3 meters) within a height range that extends from ~ 90 km to ~ 1000 km of the equatorial ionosphere. Such plasma irregularities have great influence on trans-ionospheric propagation of radio waves in a wide frequency range from VHF to UHF, and thus influence all the activities of space communications in the tropical region of Brazil. The training, development and spatial distribution of these irregularities are highly sensitive to climate change space, ie, “Space Weather”, beyond the storms and convective processes in the troposphere.

Radar was the result of the development and construction begun in INPE for several years. It transmits high power pulsed signals through a network of antenna that has 768 dipoles which allow to concentrate all the transmitted energy in a very narrow beam of radiation. The same antenna also picks up the return signals scattered by ionospheric irregularities. The maximum transmitted power (120 kW) is achieved through the use of a modular system of eight transmitters staggered to maximize the transmitted energy. Operational control of the radar is done by a computer, which also performs the acquisition, handling and processing “on line” data received from the ionosphere. The recorded data are also available for processing and further analysis. The radar has been operated in several observational campaigns since 1998 and has been collecting so routine in recent years, data on the dynamics of the equatorial electrojet.

This radar, along with the 30 MHz radar offers great opportunities for researchers to study the phenomena peculiar to the equatorial region. These, along with the radar in Peru (Jicamarca), India (Thumba) and Indonesia, are one of the few cameras of this type that exist in the world around the magnetic equator. Due to the peculiar configuration of the geomagnetic field, the Brazilian equatorial region has very different characteristics from other regions. It was for this reason that the U.S. NASA, in collaboration with INPE, held in Alcantara in 1994 when the campaign GUARÁ 26 rockets were launched (in the period from September to October) to study the equatorial electrojet and the ionospheric bubbles. This campaign had the support of a radar similar to the RESCO radar (which was brought from the USA) of Digisonde (which provided the diagnostics of the ionosphere) and the magnetometers operated by INPE in São Luís Space Observatory of the RESCO radar, which is currently in a phase of technological improvement, offers great potential to promote research environment of the Brazilian equatorial region.