e-Callisto

The e-CALLISTO (Compound Astronomical Low-cost Low-frequency Instrument for Spectroscopy and Transportable Observatory) is an European-led worldwide network which aims to allow 24 hours a day solar radio burst monitoring. The e-CALLISTO network is led by the Swiss Federal Institute of Technology Zurich (ETHZ Zurich), which works up collaborations with local host institutions which operates an e-CALLISTO SRT. (http://www.e-callisto.org/

Many CALLISTO stations have been already deployed, including more than 69 instruments in more than 38 locations with users from more than 105 countries. Figure 1 shows the geographical distribution of the e-CALLISTO Solar Radio Telescopes. Through the IHY/UNBSSI (United Nations Basic Space Science Initiative) and ISWI (International Space Weather Initiative) instrument deployment program, e-CALLISTO is able to continuously observe the solar radio spectrum for 24 hours a day through all the year.

The CALLISTO spectrometer was built in the framework of IHY2007 (International Heliophysic Year) and the ISWI by former Radio and Plasma Physics Group (Principal Investigator Christian Monstein) at Institute for Astronomy, ETH Zurich. This spectrometer is considered the standard for the e-Callisto network. The instrument natively operates between 45 and 870 MHz using a modern, commercially available broadband cable - TV tuner CD1316. The details the Callisto spectrometer main characteristics can be found on http://www.e-callisto.org/. Callisto provides scientic-class data with a remarkable low cost.

Spanish contribution to e-Callisto Network
In 2012, several Radio Frequency Interference (RFI) (background) measurements were performed in Guadalajara area (central Spain) in order to nd the most suitable location of e-Callisto Solar Radio Telescope. The RFI measurements showed the location of Peralejos de las Truchas (200 km away from Alcala de Henares) as the more suitable location with less RFI. During the last quarter of 2014, new RFI measurements were done on the area. The Figure shows the 2014 RFI measurement once the instrumental background has been substracted. The left plot of the gure shows the measurement at the University of Alcala with a lot of interferences: the University of Alcala is located at 33 km of Madrid city and 10 km from Barajas International airport. The right plot shows the RFI at OAPT. The background measurements were done with a system composed with and 25-1300 MHz Discone type antenna connected to CALLISTO spectrometer.

The Space Reseach Group (SRG) developed a prototype of an e-Callisto type SRT which was in operation for 6 months at Alcala de Henares. The prototype was designed as EA4RKU-SRT and their data are available on the e-Callisto repository. After the prototype and testing period the Solar Radio Telescope was moved to its nal location at the Peralejos de las Truchas Astronomy Observatory (OAPT from the Spanish acromym) as Melibea-SRT.

Melibea Solar Radio Telescope (Peralejos de las Truchas)

The Melibea e-Callisto type Solar Radio Telescope is operating at Peralejos de las Truchas since 01/05/2013. The location of the Melibea-SRT is at N4035' W0115' world geodetic coordinates and 1240 metres above sea level near of the village of Peralejos de las Truchas (Guadalajara).

The Melibea-SRT is based in a horizontally log-periodic antenna mounted on a robotic sun tracking system. The antenna has a forward gain of 10-12 dBi. The antenna is pointed by a Sun tracking system based on two (one azimuth and two elevation) YAESU G5500 rotors which are driven by an AVRSCOM control system. The software used for the sun tracking is the SUM provided with the SatPC32 software developed for radio amateur operators. The antenna is connected to a CALLISTO spectrometer by a 25 meters of 5D-FB coaxial cable (attenuation: 93 dB/km@200 MHz; 138 dB/km @ 400 MHz). The CALLISTO spectrometer operates in a frequency range between 45 MHz and 870 MHz with 256 channels on 1.25 ms time resolution per channel. The system is congured by the Callisto V116 software. All the software is running in an unique Windows XP workstation.

We have developed several tools: