Ken Tapping
Last November, the committee formed by the International Telecommunication Union to look at the compatibility of other radio services with the need to protect radio astronomy bands finally ended its allocated life. What came out of it was like the Curate’s egg, "good in parts". In most cases it was concluded that it is quite within the capabilities of other radio services to avoid putting interference in radio astronomy bands. There were cases, where there is a real difficulty.
A good example is the Sky TV service in Europe, which is spilling interference into the neighbouring 10.6-10.7 GHz radio astronomy band, and rendering the band more or less unusable. With the satellites in operation and dishes on almost every European windowsill, there is little that can be done unless the national administration of the country with SkY TV’s Head Office is prepared to act, which it is not. The only solution might be to move the radio astronomy allocation downwards in frequency. Fortunately, Sky TV does not operate in The band 42.5 - 43.5 GHz is an important one for radio astronomy. For some unfathomable reason, the satellite broadcasting service has been allocated the band immediately below. Discussions went late into the evenings without resolution. The solution would be a suitable guard band, plus the addition of suitable filters to satellite transmitters and radio telescope front ends. However, neither service wishes to give up any bandwidth. Certainly having a clear GHz of bandwidth in this part of the spectrum is an very important thing for radio astronomy. The result is that this situation is unresolved. These outstanding issues, together with the need to do such (unbelievably tedious) studies for radio astronomy bands above 40 GHz will almost certainly require the formation of a New Committee, so that the work can grind on. The good news is that during the studies, tools have been developed to enable satellite operators to deterimine if they will cause interference problems to radio astronomy at the design stage
Issues now becoming important are the determination of the criteria needed to protect millimeter and sub-millimeter telescopes, and the need to protect infra-red telescopes from laser communication links using the same wavelength bands. Studies have begun. Our international investment into special instruments such as Alma and the Square Kilometer Array raises the need to put around them International Radio Quiet Zones, to make them operable to their sensitivity limits over as much spectrum as possible. We have to persuade the national administrations to support this against the expected opposition, since the need to avoid squirting signals and interference at specified areas of the Earth’s surface will increase the development and operation costs of satellite systems.
Over the last few years, the increasing willingness of radio astronomers to contribute effort to protecting the pieces of the radio spectrum needed for radio astronomy to be possible has produced encouraging results. However we need to keep this going. The satellite and other operators take lobbying very seriously. Whether we like it or not, we have to as well. As a friend at Industry Canada said to me when I got into this activity, "If radio astronomy is so important, why aren’t you here in Ottawa and in Geneva saying so, and telling us why?".