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):


10.55 - 10.6  GHz:	FIXED
			MOBILE except aeronautical mobile
		 	Radiolocation

			
10.6  - 10.68 GHz:	EARTH EXPLORATION-SATELLITE (passive)
			FIXED
			MOBILE except aeronautical mobile
			RADIO ASTRONOMY
			SPACE RESEARCH (passive)
			Radiolocation
			
			5.149 5.482


10.68 - 10.7  GHz: 	EARTH EXPLORATION-SATELLITE (passive)
			RADIO ASTRONOMY
			SPACE RESEARCH (passive)
			
			5.340 5.483
			

10.7  - 11.7  GHz:	FIXED
			FIXED-SATELLITE (space-to-Earth)(Earth-to-space)  5.441  5.484A
			MOBILE except aeronautical mobile

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

Astrophysical importance of the band 10.6 - 10.7 GHz

The frequency band 10 to 15 GHz provides some of the best angular resolutions (~2 arc minutes) using many large and accurate radio telescopes. Many of the nonthermal synchrotron sources are just detectable at higher frequencies, and this frequency range gives us observational information at the highest frequency where these can be detected reliably. This high-frequency range is also important for monitoring the intensity variability of the enigmatic quasars. These objects, which could be the farthest celestial objects that we can detect and which produce surprisingly large amounts of energy, have been found to vary in intensity with periods of weeks and months. Such observations lead to estimates of the sizes of these sources, which turn out to be very small for the amount of energy they produce. The variability of quasars (and some peculiar galaxies) is more pronounced at high frequencies and observations at such frequencies facilitate the discovery and the monitoring of such events. The energy emitted during any one burst from a quasar is equivalent to completely destroying a few hundred million stars in a period of a few weeks or months. We do not yet understand the fundamental physics that can produce such events - observations of the size and variability of these sources are the only ways that can assist us in solving such problems. Such observations are now best performed in the frequency range 10 to 15 GHz.

The small sizes of the quasars are revealed from the VLBI observations mentioned earlier. Such observations are also being made in the frequency band 10.6 to 10.7 GHz. The higher frequencies provide us with better angular resolution and enable us to determine more accurately the sizes and structure of quasars.

Although the importance of the RA band at 10.60 - 10.70 GHz makes an exclusive worldwide allocation desirable (since it is one of the most important bands used for internationally coordinated observations over long baselines) the use of the exclusive band 10.68 - 10.70 GHz with downward extension with the help of local protection seems to be adequate at most observatories. However, exclusion of aeronautical mobile from the band 10.60 - 10.68 GHz is essential to safeguard this band.

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 Dish0.049 mK-272 dB(WHz-1)-202 dBW-160 dB(Wm-2)-240 dB(Wm-2Hz-1)
VLBI-192 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 10.6 - 10.7 GHz is used by the Radio Astronomy Service in:

Threats to the Radio Astronomy Service:

Last modified: March 16, 2005