The Radio Astronomy Service has a primary allocation in the band 10.6 - 10.7 GHz. The subband 10.68 - 10.7 GHz has a primary passive allocation (FN: 5.340). However, out-of-band emission into the band 10.6 - 10.7 GHz caused by the GDL-6/ASTRA-1D satellite degrades radio astronomical observations at the Effelsberg Radio Observatory, Germany, dramatically: effectively no observations can be done in this frequency domain. The GDL-6/ASTRA-1D satellites operates in the Fixed Satellite Service and uses the space-to-Earth transmissions for direct-to-home television broadcasting. In 1995 CRAF informed the operator, Société Européenne des Satellites in Luxemburg, about this harmful interference which is documented above 10.695 GHz within the passive band.
ITU-R RA769-1 gives a threshold for harmful interference in the 10.6 - 10.7 GHz band as -160 dBW/m2. The GDL-6/ASTRA-1D out-of-band emission has a spectral power flux density of -158 dBW/m2/100 kHz at 10.7 GHz, falling at about 10 dB per 4 MHz at that point. If it continues to fall at this rate, the total power into the band 10.6 - 10.7 GHz is -145.6 dBW/m2, which is 14.4 dB above the threshold mentioned, and noticeable throughout the whole radio astronomy band. Note that the limits in ITU-R RA769-1 are for terrestrial interferers with an assumed sidelobe level of the radio astronomy antenna of 0 dBi; emitters in the geostationary orbit should stay 15 dB lower in the band allocated to the Radio Astronomy Service.
The operator confirmed the validity of the complaint of CRAF.
The operator informed CRAF that he performed tests using a satellite simulator, and found that the FM uplink signals have a spectrum error after spectrum regeneration to ~ 10 GHz. The plan (explained by the operator) is that the uplink spectrum of the GDL-6/ASTRA-1D is modified to improve the spectrum at ~10.7 GHz. However, the interference is still observed.
CRAF reminded the operator of the problem during a CEPT-FM meeting in May 1996 (Newsletter 1996/2). The operator did make some improvements but so far the Effelsberg Radio Observatory is not able to resume observations in this band due to this interference.
The CEPT studied this issue in depth and did not yet come to a solution.