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):
3300 - 3400 MHz: RADIOLOCATION
5.149 5.429 5.430
National Arrangements for Radio Astronomy different from ITU-R Radio Regulations
:
- Armenia: no allocation or reference to No. 5.149
- Bulgaria: no allocation or reference to No. 5.149
- Estonia: no allocation or reference to No. 5.149
- Finland: no allocation or reference to No. 5.149
- Italy: "footnote" secondary allocation
- Liechtenstein: no allocation or reference to No. 5.149
- Luxembourg: no allocation or reference to No. 5.149
- the Netherlands: notification of use
- Russian Federation: no allocation or reference to No. 5.149
- Sweden: notification of use
- Turkey: no allocation or reference to No. 5.149
- United Kingdom: no allocation or reference to No. 5.149
Astrophysical importance of the band 3345.8 - 3352.2 MHz
Three molecular lines of the CH molecule have been detected at 3263, 3335 and
3349 MHz. These frequencies are unfortunately only allocated to radio
astronomy by No. 5.149, however the study of
interstellar CH is considered to be extremely important in understanding
the chemistry of the interstellar material. The presence of
CH suggests the existence of the molecule CH4 (methane)
which is considered one of the basic molecules for the
initial stages of the formation of life.
(see IAU list of important spectral lines)
Threshold levels of interference detrimental to radio astronomy spectral-line
observations:
| System Sensitivity (noise fluctuations) | Threshold Interference Levels |
| Temperature | Power Spectral Density | Input
Power | Power Flux Density | Spectral Power Flux Density |
| Single Dish | 2.83 mK | -254 dB(WHz-1) | -219
dBW | -183 dB(Wm-2) | -230 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 3345.8 - 3352.2 MHz is used by the Radio Astronomy Service in:
Threats to the Radio Astronomy Service:
Last modified: March 21, 2005