Significant Radio Astronomy Frequencies

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Significant Radio Astronomy Frequencies

The following radio astronomy frequency bands were recognized at the 1979 World Administrative Radio Conference. Many are shared segments, not specifically protected from interference by other authorized users, but are nevertheless generally accepted spectral regions for radio astronomical observation. The lower two segments are generally used for solar and Jupiter observations; the 73, 150 and 406 MHz segments are quite popular for pulsar detection, and the 1400 MHz band is used for hydrogen line measurements.

13.36 - 13.41 MHz
25.55 - 25.67 MHz
73.00 - 74.60 MHz
150.05 - 153.00 MHz
406.10 - 410.00 MHz
1400.0 - 1427.0 MHz

IAU Protected Segments
Contributed by Hans Brakob, K0HB
At the XXIst General Assembly of the International Astronomical Union, IAU, (Buenos Aires, July 23 - August 1, 1991) the astrophysically most important spectral lines have been carefully reviewed. The IAU listed the revision of these spectral lines as reproduced below. The IAU expressed the continued need to protect these frequency bands from in-band, band-edge and harmonic emissions, especially from space-borne transmitters.

Substance	Rest Frequency	Protected Segment	Notes (1)
Deuterium (DI)	327.3840 MHz	327.0 - 327.7 MHz
Hydrogen (HI)	1420.406 MHz	1370.0 - 1427.0 MHz	2),3)
Hydroxyl radical (OH)	1612.231 MHz	1606.8 - 1613.8 MHz	3),4)
Hydroxyl radical (OH)	1665.402 MHz	1659.8 - 1667.1 MHz	4)
Hydroxyl radical (OH)	1667.359 MHz	1661.8 - 1669.0 MHz	4)
Hydroxyl radical (OH)	1720.530 MHz	1714.8 - 1722.2 MHz	3),4)
Methyladyne (CH)	3263.794 MHz	3252.9 - 3267.1 MHz	3),4)
Methyladyne (CH)	3335.481 MHz	3324.4 - 3338.8 MHz	3),4)
Methyladyne (CH)	3349.193 MHz	3338.0 - 3352.5 MHz	3),4)
Formaldehyde (H2CO)	4829.660 MHz	4813.6 - 4834.5 MHz	3),4)
Methanol (CH2OH)	6668.518 MHz	6661.8 - 6675.2 MHz	3),6)
Ionized Helium Isotope (3HeII)	8665.650 MHz	8660.0 - 8670.0 MHz
Methanol (CH3OH)	12.178 GHz	12.17 - 12.19 GHz	3),6)
Formaldehyde (H2CO)	14.488 GHz	14.44 - 14.50 GHz	3),4)
Cyclopropenylidene (C3H2)	18.343 GHz	18.28 - 18.36 GHz	3),4),6)
Water Vapour (H2O)	22.235 GHz	22.16 - 22.26 GHz	3),4)
Ammonia (NH3)	23.694 GHz	23.61 - 23.71 GHz	4)
Ammonia (NH3)	23.723 GHz	23.64 - 23.74 GHz	4)
Ammonia (NH3)	23.870 GHz	23.79 - 23.89 GHz	4)
Silicon monoxide (SiO)	42.821 GHz	42.77 - 42.86 GHz
Silicon monoxide (SiO)	43.122 GHz	43.07 - 43.17 GHz
Carbon monosulphide (CS)	48.991 GHz	48.94 - 49.04 GHz
Deuterated formylium (DCO+)	72.039 GHz	71.96 - 72.11 GHz	3)
Silicon monoxide (SiO)	86.243 GHz	86.16 - 86.33 GHz
Formylium (H13CO+)	86.754 GHz	86.66 - 86.84 GHz
Silicon monoxide (SiO)	86.847 GHz	86.76 - 86.93 GHz
Ethynyl radical (C2H)	87.300 GHz	87.21 - 87.39 GHz	5)
Hydrogen cyanide (HCN)	88.632 GHz	88.34 - 88.72 GHz	4)
Formylium (HCO+)	89.189 GHz	88.89 - 89.28 GHz	4)
Hydrogen isocyanide (HNC)	90.664 GHz	90.57 - 90.76 GHz
Diazenylium (N2H)	93.174 GHz	93.07 - 93.27 GHz
Carbon monosulphide (CS)	97.981 GHz	97.65 - 98.08 GHz	4)
Carbon monoxide (C18O)	109.782 GHz	109.67 - 109.89 GHz
Carbon monoxide (13CO)	110.201 GHz	109.83 - 110.31 GHz	4)
Carbon monoxide (C17O)	112.359 GHz	112.25 - 112.47 GHz	6)
Carbon monoxide (CO)	115.271 GHz	114.88 - 115.39 GHz	4)
Formaldehyde (H213CO)	137.450 GHz	137.31 - 137.59 GHz	3),6)
Formaldehyde (H2CO)	140.840 GHz	140.69 - 140.98 GHz
Carbon monosulphide (CS)	146.969 GHz	146.82 - 147.12 GHz
Water vapour (H2O)	183.310 GHz	183.12 - 183.50 GHz
Carbon monoxide (C18O)	219.560 GHz	219.34 - 219.78 GHz
Carbon monoxide (13CO)	220.399 GHz	219.67 - 220.62 GHz	4)
Carbon monoxide (CO)	230.538 GHz	229.77 - 230.77 GHz	4)
Carbon monosulphide (CS)	244.953 GHz	244.72 - 245.20 GHz	6)
Hydrogen cyanide (HCN)	265.886 GHz	265.62 - 266.15 GHz
Formylium (HCO+)	267.557 GHz	267.29 - 267.83 GHz
Hydrogen isocyanide (HNC)	271.981 GHz	271.71 - 272.25 GHz
Dyazenulium (N2H+)	279.511 GHz	279.23 - 279.79 GHz
Carbon monoxide (C18O)	312.330 GHz	329.00 - 329.66 GHz
Carbon monoxide (13CO)	330.587 GHz	330.25 - 330.92 GHz
Carbon monosulphide (CS)	342.883 GHz	342.54 - 343.23 GHz
Carbon monoxide (CO)	345.796 GHz	345.45 - 346.14 GHz
Hydrogen cyanide (HCN)	354.484 GHz	354.13 - 354.84 GHz
Formylium (HCO+)	356.734 GHz	356.37 - 357.09 GHz
Dyazenulium (N2H+)	372.672 GHz	372.30 - 373.05 GHz
Water vapour (H2O)	380.197 GHz	379.81 - 380.58 GHz
Carbon monoxide (C18O)	439.088 GHz	438.64 - 439.53 GHz
Carbon monoxide (13CO)	440.765 GHz	440.32 - 441.21 GHz
Carbon monoxide (CO)	461.041 GHz	460.57 - 461.51 GHz
Heavy water (HDO)	464.925 GHz	464.46 - 465.39 GHz
Carbon (CI)	492.162 GHz	491.66 - 492.66 GHz
Water vapour (H218O)	547.676 GHz	547.13 - 548.22 GHz
Water vapour (H2O)	556.936 GHz	556.37 - 557.50 GHz
Ammonia (15NH3)	572.113 GHz	571.54 - 572.69 GHz
Ammonia (NH3)	572.498 GHz	571.92 - 573.07 GHz
Carbon monoxide (CO)	691.473 GHz	690.78 - 692.17 GHz
Hydrogen cyanide (HCN)	797.433 GHz	796.64 - 789.23 GHz
Formylium (HCO+)	802.653 GHz	801.85 - 803.85 GHz
Carbon monoxide (CO)	806.652 GHz	805.85 - 807.46 GHz
Carbon (CI)	809.350 GHz	808.54 - 810.16 GHz

Notes:

If Note 4) or Note 2) are not listed, the band limits are Doppler-shifted frequencies corresponding to radial velocities of +/- 300 km/s (consistent with line radiation occurring in our galaxy).
An extension to lower frequencies of the allocation of 1400-1427 MHz is required to allow for the Doppler shifts for HI observed in distant galaxies.
The current international allocation is not primary and/or does not meet bandwidth requirements. See: ITU-R Radio Regulations (Table 8) for more detailed information.
Because these line frequencies are also being used for observing other galaxies, the listed bandwidths include Doppler shifts corresponding to radial velocities of up to 1000 km/s. It should be noted that HI has been observed at frequencies redshifted to 500 MHz, while some lines of the most abundant molecules have been detected in galaxies with velocities up to 50 000 km/s, corresponding to a frequency reduction of up to 17%.
There are six closely spaced lines associated with this molecule at this frequency. The listed band is wide enough to permit observations of all six lines.
This line is not mentioned in Article 8 of the ITU-R Radio Regulations.

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