The Gauribidanur radioheliograph

A new radio heliograph for obtaining two-dimensional images of the solar corona sequentially at many frequencies in the range 40-150 MHz has been built by the Indian Institute of Astrophysics at the Gauribidanur Radio Observatory (lat. 13 degrees 36'12 " N and long. 77 degrees 27'07 " E) about 100 km north of Bangalore, India. This paper describes various aspects of the antenna system, receiver front end, digital hardware, the data acquisition and the calibration procedure. The performance of the instrument is illustrated with maps of the continuum emission from the undisturbed corona at different frequencies.