The CALLISTO spectrometer is a programmable heterodyne receiver ('Compound Astronomical Low frequency Low cost Instrument for Spectroscopy and Transportable Observatory'). The main applications are the observation of solar radio bursts as well as rfi-monitoring. A network has been established, wherein DLR operates three types of receivers in different spectral ranges (see Instrument specifications). Each CALLISTO station consists of an antenna, a preamplifier, a heterodyne receiver (the actual CALLISTO spectrometer) and a PC. The programmable receiver uses a modern, commercially available broadband cable TV tuner CD1316 recording frequencies from 45 to 870 MHz with a resolution of 62.5 kHz. The range can be modified to other frequencies by means of a heterodyne up-converter or down-converter. Since this can considerably vary, the type of antenna depends on the chosen frequency range.
The CALLISTO monitoring software provides FIT-files with up to 400 frequencies per sweep. The data is stored locally on each computer and can be uploaded voluntarily to the central server of the FHNW (Fachhochschule Nordwestschweiz) via FTP. Currently, about 70 stations provide data on a regular basis. Similar to GIFDS and SOFIE, CALLISTO is one of the ISWI instruments.
