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):


403   - 406    MHz:	METEOROLOGICAL AIDS
		 	Fixed
			Mobile except aeronautical mobile

			
406   - 406.1  MHz:	MOBILE-SATELLITE (Earth-to-space)
			
			5.266 5.267


406.1 - 410    MHz: 	FIXED
			MOBILE except aeronautical mobile
			RADIO ASTRONOMY
			
			5.149
			

410   - 420    MHz:	FIXED
			MOBILE except aeronautical mobile
			Space Research (space-to-space) 5.268
			


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


Astrophysical importance of the band 406.1 - 410 MHz

The band 406.1 - 410 MHz: This is an important band (see No. 5.149) for radio astronomy, but its usefulness is decreased by interference from balloon-borne transmitters which nominally operate in the band 400.15 - 406 MHz. It would be desirable to reduce the interference potential by lowering the upper limit of this meteorological aids band or by extending the radio astronomy band upwards by a few MHz so that emissions near the lower end of the band could be avoided.


Threshold levels of interference detrimental to radio astronomy continuum observations:

System Sensitivity (noise fluctuations)Threshold Interference Levels
TemperaturePower Spectral DensityInput PowerPower Flux DensitySpectral Power Flux Density
Single Dish0.96 mK-259 dB(WHz-1)-203 dBW-189 dB(Wm-2)-255 dB(Wm-2Hz-1)
Interferometer-242 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 band 406.1 - 410 MHz is used by the Radio Astronomy Service in:


Threats to the Radio Astronomy Service:


Last modified: March 21, 2005