Callisto radio spectrometer for observing the sun—Metsähovi Radio Observatory joins the worldwide observing network

The radio spectrum at MRO suffers from local electronics, broadband television, DBV-T, FM-radio, and some local data-links of nearby Schengen police communication and hence Metsähovi in the present situation is not ideal as a host site for a solar frequency agile or even to have an FFT spectrometer used at low frequencies. The general situation will be notably improved by installing the whole system at a more remote location or by improving the shielding of nearby electronic equipment. Also during the weekends, RFI-levels seem to be notably lower than during the office hours. Nevertheless it will be possible to detect strong flares with more than 50 sfu. A larger antenna with more gain would improve the situation drastically due to the fact that the signal-to-noise ratio of the solar flares would improve. Also a pre-amplifier with better noise figure and larger gain could improve the whole system´s noise temperature. The most harmful interference frequencies are generated by the local electronics. However, during the observations the antenna is pointed away from the laboratory buildings. Thus the spectra is reasonable during observations, especially at higher frequencies (>300 MHz). The first results have shown that the measurement system is operating reliably and it can detect some weak solar radio bursts.