1、 Recommendation ITU-R RA.1860(01/2010)Preferred frequency bands for radio astronomical measurements in the range 1-3 THzRA SeriesRadio astronomyii Rec. ITU-R RA.1860 Foreword The role of the Radiocommunication Sector is to ensure the rational, equitable, efficient and economical use of the radio-fre
2、quency spectrum by all radiocommunication services, including satellite services, and carry out studies without limit of frequency range on the basis of which Recommendations are adopted. The regulatory and policy functions of the Radiocommunication Sector are performed by World and Regional Radioco
3、mmunication Conferences and Radiocommunication Assemblies supported by Study Groups. Policy on Intellectual Property Right (IPR) ITU-R policy on IPR is described in the Common Patent Policy for ITU-T/ITU-R/ISO/IEC referenced in Annex 1 of Resolution ITU-R 1. Forms to be used for the submission of pa
4、tent statements and licensing declarations by patent holders are available from http:/www.itu.int/ITU-R/go/patents/en where the Guidelines for Implementation of the Common Patent Policy for ITU-T/ITU-R/ISO/IEC and the ITU-R patent information database can also be found. Series of ITU-R Recommendatio
5、ns (Also available online at http:/www.itu.int/publ/R-REC/en) Series Title BO Satellite delivery BR Recording for production, archival and play-out; film for television BS Broadcasting service (sound) BT Broadcasting service (television) F Fixed service M Mobile, radiodetermination, amateur and rela
6、ted satellite services P Radiowave propagation RA Radio astronomy RS Remote sensing systems S Fixed-satellite service SA Space applications and meteorology SF Frequency sharing and coordination between fixed-satellite and fixed service systems SM Spectrum management SNG Satellite news gathering TF T
7、ime signals and frequency standards emissions V Vocabulary and related subjects Note: This ITU-R Recommendation was approved in English under the procedure detailed in Resolution ITU-R 1. Electronic Publication Geneva, 2010 ITU 2010 All rights reserved. No part of this publication may be reproduced,
8、 by any means whatsoever, without written permission of ITU. Rec. ITU-R RA.1860 1 RECOMMENDATION ITU-R RA.1860 Preferred frequency bands for radio astronomical measurements in the range 1-3 THz (Question ITU-R 145/7) (2010) Scope This Recommendation describes spectral line and continuum radio astron
9、omical observations conducted in the frequency range between 1 000 and 3 000 GHz and recommends that administrations provide assistance in the coordination of radio astronomy observations in this frequency range. The ITU Radiocommunication Assembly, considering a) that radio astronomers study radio
10、emissions from cosmic sources at higher and higher frequencies; b) that the frequencies of observation are often determined by the spectral line frequencies of atoms and molecules that exist in astrophysical environments and that such frequencies are determined by nature; c) that the possibility of
11、carrying out observations from the surface of the Earth depends on the “windows” at which the atmosphere is sufficiently transparent; d) that the development of radio astronomy at THz frequencies is leading to technological advances, particularly in receiving techniques, and promises further importa
12、nt results; e) that frequency bands of importance to the radio astronomy service below 1 000 GHz are addressed in Recommendation ITU-R RA.314; f) that astronomical use of frequencies between 10 THz and 1 000 THz are addressed in Recommendation ITU-R RA.1630; g) that there is increasing interest in t
13、he use of the range 1 000-3 000 GHz by the radio astronomy service; h) that the International Astronomical Union (IAU) is maintaining and updating the list of spectral lines of the greatest importance to radio astronomy at frequencies up to 3 000 GHz; j) that account should be taken of the Doppler s
14、hifts of the lines, due to the relative motion of cosmic source and observer; k) that radio astronomers also have a need to make continuum observations at frequencies above 1 000 GHz, and that the bands used for such observations from the ground are determined by the atmospheric windows where lower
15、attenuation occurs; l) that the use of radio telescopes from space platforms, conducted under the space research service (passive), provides access to the entire radio spectrum, including portions of the spectrum not accessible from the Earth due to absorption in the atmosphere; 2 Rec. ITU-R RA.1860
16、 m) that protections are afforded to the radio astronomy service in bands below 275 GHz by virtue of the Table of Frequency Allocations and in bands between 275 and 1 000 GHz by virtue of No. 5.565 of the Radio Regulations (RR), recommends 1 that administrations provide assistance in the coordinatio
17、n of radio astronomy observations in bands between 1 000 GHz and 3 000 GHz, particularly those listed in Table 1 (for space-based observations) and Table 3 (for ground-based observations). Annex 1 1 Spectral lines of astronomical interest Table 1 lists the non-Doppler-shifted (“rest”) frequencies of
18、 the spectral lines emitted by a variety of molecules of astrophysical interest. From the rest frequency, an approximate range of frequencies over which the lines may be observed is provided, based upon typical Doppler shifts that are observed due to radial motion of the cosmic source toward or away
19、 from the observer. In the table, an assumed Doppler range of 300 km/s is used. The ranges listed in Table 1 are suggested minimum bands. It should be noted that because of high sensitivities of the radio astronomical observations so many spectral lines have been observed from extragalactic objects,
20、 up to z 6 or higher (here, z denotes the “red-shift”, defined by z = (obs 0)/0, where obsis the observed wavelength and 0is the non-Doppler shifted wavelength). Therefore highly red-shifted spectral line observations need to be taken care of. The source data for Table 1, which was approved by the G
21、eneral Assembly of the International Astronomical Union (IAU) in 2009, were derived from observational studies of submillimetre spectral line emission towards two molecule-rich regions of the Milky Way Galaxy1,2; from the JPL Molecular Spectroscopy database3; and from a web-based catalogue of molecu
22、lar spectral lines (the Cologne Database for Molecular Spectroscopy) maintained by the University of Cologne, Germany4. 2 Atmospheric absorption At millimetre and submillimetre wavelengths, an important factor for ground-based observing is the degree to which the atmosphere attenuates radio signals.
23、 Attenuation of signals in the 1 000-3 000 GHz frequency range is due mainly to absorption by water vapour, and to a lesser extent by oxygen, nitrogen and ozone. 1POLEHAMPTON, E. T. et al. 2007 The ISO LWS high-resolution spectral survey towards Sagittarius B2*. Monthly Notices of the Royal Astronom
24、ical Society (MNRAS), Vol. 377, p. 1122. 2LERATE, M. R. et al. 2006 A far-infrared molecular and atomic line survey of the Orion KL region. Monthly Notices of the Royal Astronomical Society (MNRAS), Vol. 370, p. 597. 3http:/spec.jpl.nasa.gov/. 4http:/www.astro.uni-koeln.de/cdms/. Rec. ITU-R RA.1860
25、3 For ground-based observatories, atmospheric attenuation reduces the observed signal level of emission coming from cosmic sources and adds thermal noise to the received signal. For this reason, millimetre and submillimetre radio astronomy stations are located at high, dry sites. Despite optimizing
26、the observing location, the level of attenuation is so high over portions of the 1 000-3 000 GHz range that, with the exception of a few “windows”, many observations in this spectral region can only be conducted from space. Table 1 notes those spectral lines that would only be observable from space
27、due to high atmospheric attenuation within the suggested minimum band. Figure 1 is an example of the transmittance on a vertical path through the atmosphere (i.e. looking straight up along the shortest line of sight through the atmosphere), over the frequency range 1 000-3 000 GHz, at a good astrono
28、mical observing site. The data were calculated using the am atmospheric model5, assuming the following inputs6: Site location: Cerro Sairecabur, approximately 35 km north-northwest of the location of the Atacama Large Millimeter/submillimeter Array (ALMA) site at Chajnantor, Chile. Elevation: 5 525
29、m. Barometric pressure at ground: 532 mbar. Ground temperature: 285 K. Atmospheric pressure/temperature profile: Based on data acquired over 187 radiosonde flights in the area over the period 1998-2002. The ozone profile was based on NASA ozone-sonde flights over Galapagos, Ecuador, during the same
30、period. Total precipitable water vapour (PWV) content: 0.25 mm. Based on extended measurement campaigns, this site was determined to have a PWV at or below this value approximately 25% of the time. The calculated transmittance curve agrees well with observed atmospheric brightness temperatures obtai
31、ned with Fourier transform spectrometer (FTS) measurements at the site. Table 2 lists the frequency ranges over which the atmospheric transmittance of Fig. 2 exceeds 20%, 10%, 5%, and 1% (Fig. 2 is a graphical representation of the data in Table 2). Lower transmittances will decrease the received si
32、gnal strength from cosmic sources due to atmospheric absorption, and increase the radio astronomy system noise temperature due to thermal emission from the atmosphere. Therefore, larger transmittances are highly desirable for ground-based radio astronomical measurements, although useful ground-based
33、 observations of relatively strong cosmic emissions may be made for transmittances as low as 5%, and possibly lower. 5See http:/www.cfa.harvard.edu/spaine/am/ (queried June 2008). 6Specifically, the calculations employed the Sairecabur profile of Example 4 of: PAINE, S. 2004 The am Atmospheric Model
34、. Submillimeter Array Technical Memo #152 (Revision 3). Available at http:/sma-www.harvard.edu/private/memos/tech_no.html (queried June 2008). 4 Rec. ITU-R RA.1860 TABLE 1 Astrophysically most important spectral lines in the frequency range between 1 000 and 3 000 GHz Species Rest frequency(GHz) Sug
35、gested minimum frequency (GHz) Suggested maximum frequency (GHz) Remarks Consolidated minimum frequency (GHz) Consolidated maximum frequency (GHz) Water vapour (H218O) 1 003.278 1 002.274 1 004.281 G 1 002.274 1 004.281 Heavy water (HDO) 1 009.945 1 008.935 1 010.955 G 1 008.935 1 010.955 Azanyliden
36、ium (NH+) 1 012.524 1 011.511 1 013.537 G 1 011.511 1 013.537 Carbon monosulphide (CS) 1 027.314 1 026.287 1 028.341 G 1 026.287 1 028.341 Hydroxylium (OH+) 1 033.119 1 032.085 1 034.152 G 1 032.085 1 034.152 Carbon monoxide (CO) 1 036.912 1 035.875 1 037.949 G 1 035.875 1 037.949 Hydrogen cyanide (
37、HCN) 1 062.983 1 061.920 1 064.046 1 061.920 1 064.046 Formylium (HCO+) 1 069.694 1 068.624 1 070.764 1 068.624 1 070.764 Carbon monosulphide (CS) 1 076.078 1 075.002 1 077.154 1 075.002 1 077.154 Sulfhydrylium (SH+) 1 082.909 1 081.826 1 083.993 1 081.826 1 083.993 Water vapour (H218O) 1 095.627 1
38、094.532 1 096.723 Carbon monoxide (C18O) 1 097.163 1 096.066 1 098.260 Water vapour (H2O) 1 097.365 1 096.267 1 098.462 1 094.532 1 098.462 Carbon monoxide (13CO) 1 101.350 1 100.248 1 102.451 Water vapour (H218O) 1 101.698 1 100.597 1 102.800 1 100.248 1 102.800 Water vapour (H2O) 1 113.343 1 112.2
39、30 1 114.456 Water cation (H2O+) 1 115.059 1 113.943 1 116.175 1 112.230 1 116.175 Carbon monosulphide (CS) 1 124.820 1 123.696 1 125.945 1 123.696 1 125.945 Water vapour (H218O) 1 136.704 1 135.567 1 137.840 1 135.567 1 137.840 Hydrogen cyanide (HCN) 1 151.452 1 150.301 1 152.603 Carbon monoxide (C
40、O) 1 151.985 1 150.833 1 153.137 Water vapour (H2O) 1 153.127 1 151.974 1 154.280 1 150.301 1 154.280 Water vapour (H2O) 1 158.324 1 157.165 1 159.482 Formylium (HCO+) 1 158.727 1 157.568 1 159.886 1 157.165 1 159.886 Heavy water (HDO) 1 161.953 1 160.791 1 163.115 Water vapour (H2O) 1 162.912 1 161
41、.749 1 164.075 Heavy water (HDO) 1 164.770 1 163.605 1 165.935 1 160.791 1 165.935 Rec. ITU-R RA.1860 5 TABLE 1 (continued) Species Rest frequency(GHz) Suggested minimum frequency (GHz) Suggested maximum frequency (GHz) Remarks Consolidated minimum frequency (GHz) Consolidated maximum frequency (GHz
42、) Ammonia (NH3) 1 168.452 1 167.283 1 169.620 1 167.283 1 169.620 Carbon monosulphide (CS) 1 173.539 1 172.366 1 174.713 1 172.366 1 174.713 Heavy water (HDO) 1 180.324 1 179.143 1 181.504 Water vapour (H218O) 1 181.394 1 180.213 1 182.575 1 179.143 1 182.575 Water vapour (H218O) 1 188.863 1 187.674
43、 1 190.052 1 187.674 1 190.052 Water vapour (H218O) 1 199.006 1 197.807 1 200.205 1 197.807 1 200.205 Carbon monoxide (C18O) 1 206.725 1 205.519 1 207.932 Water vapour (H2O) 1 207.639 1 206.431 1 208.846 1 205.519 1 208.846 Carbon monoxide (13CO) 1 211.330 1 210.118 1 212.541 1 210.118 1 212.541 Amm
44、onia (NH3) 1 214.859 1 213.644 1 216.073 Ammonia (NH3) 1 215.245 1 214.030 1 216.460 Water vapour (H218O) 1 216.850 1 215.634 1 218.067 Heavy water (HDO) 1 217.258 1 216.041 1 218.476 1 213.644 1 218.476 Carbon monosulphide (CS) 1 222.234 1 221.012 1 223.456 1 221.012 1 223.456 Water vapour (H2O) 1
45、228.789 1 227.560 1 230.018 Heavy water (HDO) 1 230.403 1 229.173 1 231.633 1 227.560 1 231.633 Hydrogen cyanide (HCN) 1 239.895 1 238.655 1 241.134 1 238.655 1 241.134 Formylium (HCO+) 1 247.735 1 246.487 1 248.982 1 246.487 1 248.982 Heavy water (HDO) 1 259.072 1 257.813 1 260.331 G Heavy water (H
46、DO) 1 261.469 1 260.208 1 262.731 G 1 257.813 1 262.731 Carbon monoxide (CO) 1 267.014 1 265.747 1 268.282 G Heavy water (HDO) 1 267.043 1 265.776 1 268.310 G 1 265.747 1 268.310 Carbon monosulphide (CS) 1 270.903 1 269.632 1 272.174 G 1 269.632 1 272.174 Heavy water (HDO) 1 277.676 1 276.398 1 278.
47、954 G 1 276.398 1 278.954 Heavy water (HDO) 1 291.642 1 290.351 1 292.934 G Heavy water (HDO) 1 293.372 1 292.079 1 294.666 G 1 290.351 1 294.666 Heavy water (HDO) 1 297.805 1 296.507 1 299.103 G 1 296.507 1 299.103 6 Rec. ITU-R RA.1860 TABLE 1 (continued) Species Rest frequency(GHz) Suggested minim
48、um frequency (GHz) Suggested maximum frequency (GHz) Remarks Consolidated minimum frequency (GHz) Consolidated maximum frequency (GHz) Carbon monoxide (C18O) 1 316.244 1 314.928 1 317.560 G 1 314.928 1 317.560 Carbon monosulphide (CS) 1 319.545 1 318.226 1 320.865 Carbon monoxide (13CO) 1 321.266 1
49、319.944 1 322.587 Water vapour (H2O) 1 322.065 1 320.743 1 323.387 1 318.226 1 323.387 Hydrogen cyanide (HCN) 1 328.308 1 326.980 1 329.637 G 1 326.980 1 329.637 Formylium (HCO+) 1 336.714 1 335.378 1 338.051 G 1 335.378 1 338.051 Water vapour (H218O) 1 340.739 1 339.398 1 342.080 G 1 339.398 1 342.080 Heavy water (HDO) 1 353.777 1 352.423 1 355.130 G 1 352.423 1 355.130 Carbon monosulphide (CS) 1 368.160 1 366.792 1 369.528 G Trihydrogen (H2D+) 1 370.085 1 368.715 1 371.455 G 1 366.792 1 371.455 Carbon monoxide (CO)
