The Committee on Radio Astronomy Frequencies (CRAF) is a committee of
the European Science Foundation (ESF).
The Russian LEO satellite communication system GONETS was developed within the framework of the Russian Federal Space Program under the guidance of the Russian Space Agency. The GONETS system provides a fixed or mobile facility to receive and transmit messages from any point of the globe, providing a personal communications service.
The system was planned before the allocation of frequencies for these services by the WARC-92, and the 300-400 MHz band is reserved for military use in most countries. The system was allocated secondary status by the ITU. VHF and UHF frequencies are employed, outside the WARC-92 bands. Data rates are 2400bps on the uplink and 9600bps on the downlink.
The number of satellites planned for the systems is 36 with an orbit at 1500 km altitude with individual cell sizes 500-800km diameter. The space-to-Earth transmissions fall within the 387 - 390 MHz band.
Footnote 5.208A regulates the protection of the radio astronomy bands 150.05-153 MHz, 322-328.6 MHz, 406.1-410 MHz, and 608-614 MHz from unwanted emissions from space stations in mobile satellite services using the frequency band 387-390 MHz.
The threshold levels of interference detrimental to single-dish radio astronomy continuum observations given in Recommendation ITU-R RA.769 for the bands mentioned in footnote 5.208A are given in the following table.
| Frequency band (MHz) | Spectral power flux density (dB(Wm-2Hz-1)) |
| 150.05 - 153 | -259 |
| 322 - 328.6 | -258 |
| 406.1 - 410 | -255 |
| 608 - 614 | -253 |
These levels apply to interference from the aggregate of the transmissions of the GONETS satellites in view of a radio astronomy station.
From the system parameters of the GONETS system, in particular its orbital parameters, it can be derived that the visibility radius of a GONETS satellite is of the order of 4500 km, which implies that a Europe-wide approach is necessary to study the compatibility issue between the GONETS system and the radio astronomy service, taking into account the information given above and relevant ITU-R documentation.
CRAF has requested CEPT WGSE project team SE28 to study the compatibility of the GONETS systems with radio astronomy.
CEPT WGSE project team SE21 concluded in 2002 that based on the study results, "it is shown that the unwanted emissions from GONETS systems transmitting space-to-Earth in the band 387-390 MHz will meet the RAS protection criteria operating in the band 406.1 - 410MHz. Before reaching a definitive conclusion on this matter, the parameters used in these compatibility analyses should be confirmed by the Russian Administration. In particular, it could be useful for future work within SE 21 to obtain information on the techniques which are used to reach a 100dB rejection between the wanted emissions level and the unwanted emissions level.
Studies completed in CEPT showed that with the considered rejection filter at the space system radio astronomy operating near 0.4 GHz is adequately protected.
The frequency plan for GONETS is as follows:
| service links | 387 - 390 MHz (space-to-Earth) | 312 - 315 MHz (Earth-to-space) |
| service links | 1541.0 - 1541.9 MHz (space-to-Earth) | 1624.5 - 1643.4 MHz (Earth-to-space) |