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):


40.5  -  41    GHz:	FIXED
			FIXED-SATELLITE (space-to-Earth)
			BROADCASTING
			BROADCASTING-SATELLITE
			Mobile

			5.547


41    -  42.5  GHz:	FIXED
			FIXED-SATELLITE (space-to-Earth)  5.516A
			BROADCASTING
			BROADCASTING-SATELLITE
			Mobile

			5.547 5.551F 5.551H 5.551I

	 
42.5  -  43.5   GHz:	FIXED
			FIXED-SATELLITE (Earth-to-space) 5.552
			MOBILE except aeronautical mobile
			SPACE RESEARCH (passive)
			RADIO ASTRONOMY

			5.149 5.547


43.5   -  47    GHz:	MOBILE
			MOBILE-SATELLITE
			RADIONAVIGATION
			RADIONAVIGATION-SATELLITE

			5.554

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

Astrophysical importance of the band 42.5 - 43.5 GHz

The band 42.5-43.5 MHz is used for both continuum and spectral line observations.

The frequency region between 42.5 and 49 GHz contains important spectral lines of some diatomic and other molecules. The lines of SiO indicate maser emission, the mechanism of which is not understood but which extends over a wide range of excitation in the SiO molecule as evidenced by the detection of the v = 3 transition.

The lines of CS and its less comon isotopes C33S, C34S, 13CS, have been shown to be constituents of both giant molecular clouds and cool dark clouds. Since the J = 1 -> 0 transition arises in the lowest possible energy levels of CS, this molecule will become increasingly important in probing cool clouds. Other molecules with detected transitions in this frequency range include H2CO, CH3OH and OCS.

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 Dish2.84 mK-254 dB(WHz-1)-207 dBW-153 dB(Wm-2)-210 dB(Wm-2Hz-1)

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 Dish0.064 mK-271 dB(WHz-1)-191 dBW-137 dB(Wm-2)-227 dB(Wm-2Hz-1)
Interferometer-200 dB(Wm-2Hz-1)
VLBI-173 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 42.5 - 43.5 GHz is used by the Radio Astronomy Service by:

Threats to the Radio Astronomy Service:

Last modified: March 21, 2005