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):


1350  - 1400  MHz:	FIXED
			MOBILE
			RADIOLOCATION
			
			5.149 5.338 5.339 5.339A
			

1400  - 1427  MHz: 	EARTH EXPLORATION-SATELLITE (passive)
			RADIO ASTRONOMY
			SPACE RESEARCH (passive)
			
			5.340 5.341
			

1427  - 1429  MHz:	SPACE OPERATIONS (Earth-to-space)
			FIXED
			MOBILE except aeronautical mobile
			
			5.341

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

Astrophysical importance of the band 1400.0 - 1427.0 MHz

The band 1400.0 - 1427.0 MHz is the most important band for studies of the hydrogen line and for continuum observations and should be maintained at the level of No. 5.340.

The 21-cm line (1420.406 MHz) of neutral atomic hydrogen is the most important radio spectral line. Since its discovery in 1951, observations of this line have been used to study the structure of our Galaxy and other galaxies. Because of Doppler shifts, the frequency range for observing this emission necessarily ranges from ~1330 to ~1430 MHz.

Numerous and detailed studies of neutral hydrogen distribution in our Galaxy and in other galaxies are being made. Such studies are being used to investigate the state of cold interstellar matter, the dynamics, kinematics and distribution of the gas, the rotation of our Galaxy and other galaxies and to make estimates of the masses of other galaxies.

The 21-cm neutral hydrogen emission is relatively strong and with modern instrumentation it is detectable in all directions in our Galaxy and from a very large percentage of the nearby galaxies.

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 Dish3.48 mK-253 dB(WHz-1)-220 dBW-196 dB(Wm-2)-239 dB(Wm-2Hz-1)
Interferometer-222 dB(Wm-2Hz-1)
VLBI-199 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 Dish0.095 mK-269 dB(WHz-1)-205 dBW-180 dB(Wm-2)-255 dB(Wm-2Hz-1)
Interferometer-238(dBWm-2Hz-1)
VLBI-209 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 1400.0 - 1427.0 MHz is used by the Radio Astronomy Service in:

Threats to the Radio Astronomy Service:

Last modified: March 16, 2005