International Network of Solar Radio Spectrometers, a Space Weather Instrument Array

e-Callisto logo


Map of current distribution of Callisto instruments in October 2018. Update rate ~15 minutes, press reload to see latest status. One dot can represent up to 5 instruments.

Statistics: more than 150 instruments at more than 90 locations worldwide.

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 designed 2006 in the framework of IHY2007 and ISWI by Christian Monstein (PI) as member of the former Radio Astronomy Group (RAG) 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-, PERL- and Python-routines were written.
Many CALLISTO instruments have already been deployed, including: 10 spectrometers in India (2 in Ooty, 1 in Gauribidanur, 1 in Pune, 1 in Ahmedabad, 1 in Sangli, 2 in Bagalore, 1 in Nashik and 1 in Udaipur), one in Badary near Irkutsk, Russian Federation, two in Daejeon/South Korea, three in Australia (Adelaide, Melbourne and Heathcote), two in Hawaii, two in Mexico, one in Costa Rica, two in San Jose dos Campos/Brazil, three in Mauritius, 5 in Birr/Ireland, one in Ondrejov/Czech Republic, two in Ulaan Baatar/Mongolia, one in Germany (Essen), two in Anchorage/Alaska, two in Almaty/Kazakhstan, one in Cairo/Egypt, one in Nairobi/Kenya, one in Sri Lanka, four in Italy (3 in Trieste and 1 in Turin), two in Slovakia (Hurbanovo and Rotztoky), two in Humain/Belgium, 4 in Metsähovi/Finland, 8 in Switzerland (5 in Bleien, 1 in Zurich, 2 in Freienbach), 4 in Spain, 5 in Malaysia, 3 in Indonesia (Sumedong, Tomohon and Biak), one in Glasgow/Scotland/UK, one in Peru, one in Kigali/Rwanda, one in Pakistan, 2 in Denmark, one in Japan, one in South Africa, two in Kangerlussuaq/Greenland, 6 in Austria, one in Montevideo/Uruguay, two in Norway, one in Nepal and two in Ethiopia (Addis Ababa and Mekelle). 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 perform 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 ETH Global, formerly known as North-South Center of ETH Zurich and a few private sponsors.

  1. COSPAR Workshop Ethiopia 2018
  2. 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)
  3. Ordering link for new Callisto spectrometers from Whitham D. Reeve, Anchorage, Alaska
  4. Logos with different background: white  black   yellow1   yellow2
  5. Requests for quotation for Callisto instruments and options to cmonstein(at)swissonline.ch with subject = RFQ Callisto
  6. Donations via PayPal to maintain this website and data archive at FHNW are always welcome.
  7. Testsite with L-band LightCurves
  8. Frequency allocation Switzerland at OFCOM

Statistics about local radio interference rfi between 10 MHz and 1427 MHz:
RFI-map, derived from FIT-files. Color is proportional to the skewness  of a 2-dimensional FIT-file. Data  present  the 200 best channels out of 13'200  possible channels of the frequency range of Callisto. This plot is kind of optimistic case in terms of rfi.

Skewness, derived from FIT-files which is a selection of the best 200 channels out of 13'200 possible channels.

RFI-map, derived from spectral overview.  Color is proportional to (mean-rfi - quiet Sun flux), so it's a measure for minimum antenna gain to observe quiet Sun at current rfi-level. Spectral overview takes into account all possible 13'200 channels in the whole spectrum of Callisto.

rfi from ovs
Y-axis shows the average minimum antenna gain which is required to observe the quiet Sun at local mean level of rfi.
Interference level (left plots) taken from a single 15 minute FIT-file per location of the e-Callisto network in April 2016. Uruguay shows the highest level of interference. Best ones with low interference level are the ones on the right side of the bar-plot. Purple areas in the left map denote to a two-dimensional skewness level in rfi over the whole spectrum during 15 minuts of observations (without solar bursts). Skewness is a measure for the deviation from Gaussian noise distribution.The lower the skewness interference level, the better in general is 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. Sensitivity will be analyzed later, when sufficient bursts are available with known flux.
Two plots on the right side show a more pessimistic case taken from spectral overviews (OVS). The average value of rfi-flux minus quiet Sun flux ist presented. It gives an impression how many antenna gain on average is required to observe the quiet Sun flux with Callisto.

xray   latest  STEREO   
Solar Activity now (courtesy SWPC/NOAA) and GSFC/NASA.

Version: 2018-11-14
Responsible: Christian Monstein cmonstein(at)swissonline.ch