Answer: is site specific co-ordination with radio astronomy stations a mitigation factor in co-ordination issues with space systems?

For reasons of Administrative transparency and public understanding, ITU-R Recommendations and publicly available technical information serve as basis in Administrative co-ordination work.

Dependent on the antenna system of the space station co-ordination with radio astronomy stations could be sought considering the footprint of the space station or the visibility of the space station. The usual dimensions of such a footprint imply already that emissions from this footprint shine on several European radio astronomy stations at the same time because of the geographic density of radio astronomy stations in this region. The sensitivity of radio astronomy receivers implies that transmissions through sidelobes of the transmitting antenna of the space station can usually not be neglected, in particular for transmission by active antennas. It is therefore not practicable in Europe to co-ordinate between space stations and radio astronomy stations on a site by site basis – for other regions similar arguments apply.

Furthermore, VLBI observations require identical co-ordination for all radio astronomy stations participating in the VLBI network to maintain the VLBI quality.

The requirement of a clear and simple co-ordination between the space system and a radio astronomy station, requires a single conclusion that is geographically widely applicable to provide adequate protection to all potential victim applications (including the most sensitive). Moreover, the conclusions from the co-ordination work must apply to all (potentially) interested operators. This implies that adopting consequences based on site-related test results will result in a great and likely impractical burden on the operator of the space system and in avoidable complications for Administrative co-ordination work.

Therefore, unless other techniques become available, site specific co-ordination with radio astronomy stations cannot be a practicable mitigation factor in co-ordination issues with space systems.

Committee on Radio Astronomy Frequencies