International Network of Solar Radio Spectrometers

e-Callisto logo


Map of current distribution of Callisto instruments in November 2015

Red triangles: locations provide data, orange star: locations do not provide data yet/anymore

Statistics: more than 116 instruments in more than 66 locations with users from more than 120 countries

Callisto stands for: Compound Astronomical Low cost Low frequency Instrument for Spectroscopy and Transportable Observatory
type II
Type II burst (Ooty)

The CALLISTO spectrometer is a programmable heterodyne receiver built in the framework of IHY2007 and ISWI by former Radio and Plasma Physics Group (PI Christian Monstein) at ETH Zurich, Switzerland. The main applications are observation of solar radio bursts and rfi-monitoring for astronomical science, education and outreach. The instrument natively operates between 45 and 870 MHz using a modern, commercially available broadband cable-TV tuner CD1316 having a frequency resolution of 62.5 KHz. The data obtained from CALLISTO are FIT-files with up to 400 frequencies per sweep. The data are transferred via a RS-232 cable to a computer and saved locally. Time resolution is 0.25 sec at 200 channels per spectrum (800 pixels per second). The integration time is 1 msec and the radiometric bandwidth is about 300 KHz. The overall dynamic range is larger than 50 dB. For convenient data handling several IDL- and Python-routines were written.
Many CALLISTO instruments have already been deployed, including: 5 spectrometers in India (2 in Ooty, 1 in Gauribidanur, 1 in Pune, 1 in Ahmedabad), one in Badary near Irkutsk, Russian Federation, two in South Korea, three in Australia (Perth, Melbourne and Heathcote), two in Hawaii, two in Mexico, one in Costa Rica, two in Brazil, three in Mauritius, four in Ireland, one in Czech Republic, two in Mongolia, four in Germany, two in Alaska, two in Kazakhstan, one in Cairo, one in Nairobi, one in Sri Lanka, three in Trieste, one in Hurbanovo/Slovakia, two in Belgium, two in Finland, 8 in Switzerland, one in Sardinia, three in Spain, 5 in Malaysia, two in Indonesia, one in Scotland/UK one in Roztoky/Slovakia, one in Peru, one in Rwanda, one in Pakistan, one in Denmark, one in Japan, one in South Africa and one in Uruguay. Through the IHY/UNBSSI and ISWI instrument deployment program, CALLISTO is able to continuously observe the solar radio spectrum for 24h per day through all the year. All Callisto spectrometers together form the e-Callisto network. Callisto in addition is dedicated to do radio-monitoring within its frequency range with 13'200 channels per spectrum. The frequency range can be expanded to any range by switching-in a heterodyne up- or a down-converter.
Instrument deployment including education and training of observers was financially supported by SNF, SSAA, NASA, Institute for Astronomy and North-South Center of ETH Zurich and a few private sponsors.

  1. Raster fly map of the sun with a 5m dish attached to a Callisto spectrometer between 950 MHz and 1260 MHz: contour-plot (4'579KB),  surface-plot (16'023KB). Raster fly map of sky background 12° x 12° (15'357KB)
  2. Victor Herreros Radio Astronomy Blog
  3. Ordering link for new Callisto spectrometers from Whitham D. Reeve, Anchorage, Alaska
  4. Logos with different background: white  black   yellow1   yellow2
  5. Quotation for Callisto instruments and options on request to monstein(at)astro.phys.ethz.ch with subject = RFQ Callisto
  6. Donations via PayPal to maintain this website and data archive at FHNW are always welcome.

Statistics about local radio interference rfi between 45 MHz and 870 MHz:
Interference level (rfi) taken from a single 15 minute FIT-file per location of the e-Callisto network. South-Korea, Alaska, Mexico and Europe show the highest level of interference. Best ones with low interference level are Spain, Roswell NM, Mauritius, Sri Lanka, Ireland, Mongolia, Krim and Kazakhstan. Purple areas denote to a two-dimensional one sigma level in rfi which are higher than ~6 dB over the whole spectrum during 15 minuts of observations (without solar bursts).
Assumptions: Antenna gain with respect to rfi 0 dB, noise figure of pre-amplifer ~ 1dB at reference temperature of ~300 Kelvin. The lower the one sigma interference level, the better in general the overall data quality. But it does NOT tell anything about the sensitivity of an individual instrument with respect to a solar burst. Sensitivity concerning solar bursts strongly depends on whether the instrument is connected to a large or to a small antenna and whether it can be positioned to the sun.

Version: 2015-11-06
Responsible: Christian Monstein monstein(at)astro.phys.ethz.ch