Data Description and Calibration

The system began operation in mid-1994. Since the level of solar activity has been low, only about a dozen type II bursts have been observed thus far. All of them have stopped within the observed frequency range. Hundreds of type III bursts have been observed from 37 MHz down to the ionospheric cut-off. This cut-off is usually 4 to 8 MHz but the cut-off frequency depends strongly upon the zenith distance of the Sun. The 3 MHz limit to the observed frequency range ensures that any emission that can possibly get through the ionosphere in daytime will be observed. When the cut-off has been below 3 MHz late at night, some bursts, believed to be from Jupiter, have been observed down to the 3 MHz limit of observing range.

The response of the receiving system has been carefully calibrated with a thermionic diode and the antenna gain has been estimated theoretically. The polar galactic background spectrum has been observed late at night and this observed galactic spectrum agrees well with calibrated, fixed-frequency measurements made by other observers. Appreciable ionospheric absorption occurs below 15 MHz in daytime. In order to estimate and correct for this effect, during data analysis an apparent galactic background spectrum is determined for a time adjacent to the solar burst. This apparent spectrum is then compared with an archived, absorption- free spectrum that was previously observed at the same Right Ascension late at night, and the amount of daytime absorption is then estimated.

б© Copyright Astronomical Society of Australia 1997