Committee on Radio Astronomy Frequencies

The Committee on Radio Astronomy Frequencies (CRAF) is a committee of the European Science Foundation (ESF).

Frequency band allocated to the Radio Astronomy Service:

ITU-RR allocations (+ footnotes):

22.5  - 22.55  GHz:	FIXED
			MOBILE
			

22.55 - 23.55  GHz:	FIXED
			INTER-SATELLITE
			MOBILE
			
			5.149 5.532
			
			
23.55 - 23.6   GHz:	FIXED
			MOBILE

National Arrangements for Radio Astronomy different from ITU-R Radio Regulations:

Astrophysical importance of the bands 22.81 - 22.86 GHz and 23.07 - 23.12 GHz

The band 22.81 - 22.86 GHz is of importance for studies of a non-metastable ammonia line and two lines of methyl formate. Sharing with the other services should be possible in region 1, when the provisions of No 5.149 are taken into account. But in region 2 and 3 the band is (also) allocated to the Broadcasting Satellite Service. The Radio Astronomy Service will no longer be able to use this band when this service starts operating in this band. Radio astronomers are very much in favour of keeping the status in region 1 and moreover wish that this allocation should become worldwide.

The band 23.07 - 23.12 GHz is of special importance for studies of ammonia lines. The present sharing situation and the provisions of No. 5.149 should be sufficient to provide satisfactory local protection for observatories, but there is a highly interesting methanol maser line immediately above the protected band at 23.121 GHz. Extending the allocation by a small amount to cover this line is considered useful with respect to the increasing active use of this part of the spectrum.

Threshold levels of interference detrimental to radio astronomy spectral-line observations:

System Sensitivity (noise fluctuations)Threshold Interference Levels
TemperaturePower Spectral DensityInput PowerPower Flux DensitySpectral Power Flux Density
Single Dish2.91 mK-254 dB(WHz-1)-210 dBW-162 dB(Wm-2)-216 dB(Wm-2Hz-1)

NOTE:

For further details the reader is referred to ITU-R Recommendation RA769. It should, however, be noted that the observed spectral power flux densities are much lower than the harmful interference levels because they are made in the main beam of the radio astronomy antennas whereas the harmful levels correspond to reception in the sidelobes, i.e. the differences are related to the gain of the antennas. The differences can be of the order of 50 to 80 dB W m-2 Hz-1 (see ITU-R "Handbook on Radio Astronomy", 1995/2003, chapter 4).

In Europe, the bands 22.81 - 22.86 GHz and 23.07 - 23.12 GHz are used by the Radio Astronomy Service in:

Threats to the Radio Astronomy Service:

Last modified: March 16, 2005