Handbook of Frequency Allocations and Spectrum Protection for Scientific Uses: Second Edition (2015)

D

International Astronomical Union Spectral Lines of Most Importance Between 300 and 1000 GHz

At each triennial meeting of the General Assembly, the International Astronomical Union (IAU) carefully reviews the list of astrophysically most important spectral lines that it maintains. The IAU expresses the need to protect these frequency bands from in-band, band-edge, and harmonic emissions, especially from spaceborne transmitters.

In preparation for World Radiocommunication Conference 2000, which revised the allocations above 71 GHz, a millimeter-wavelength working group of the Scientific Committee on Frequency Allocations for Radio Astronomy and Space Science (IUCAF) examined all then-known transitions in the millimeter and submillimeter wavebands. The working group selected a limited number of the astrophysically most important spectral lines to supplement the earlier lists, such as those produced by the IAU, to be used in allocating frequency bands to the Radio Astronomy Service. Spectral lines between 300-1000 GHz are listed in Table D.1. Unless otherwise noted, the band limits are Doppler-shifted frequencies corresponding to radial velocities of ±300 km/s, consistent with line radiation occurring in our Milky Way galaxy. Although no formal frequency allocations are established above 275 GHz, the International Telecommunication Union (ITU) Radio Regulation 5.565 urges administrations to take all practicable steps to protect passive services from harmful interference in the frequency range of 275-1000 GHz. Of particular note are the following frequency bands, which are identified for passive use by the Radio Astronomy Service: 275-323 GHz, 327-371 GHz, 388-424 GHz, 426-442 GHz, 453510 GHz, 623-711 GHz, 795-909 GHz, and 926-945 GHz. These frequency bands correspond to atmospheric “windows” (see Figure 2.6) that permit ground-based observations of cosmic sources from high, dry sites.

TABLE D.1 The Most Important Spectral Lines Between 300 and 1000 GHz

NOTES:

1. The band limits are the Doppler-shifted frequencies corresponding to radial velocities of ±300 km/s (consistent with line radiation occurring in our Milky Way galaxy).

2. These lines are observable only outside the atmosphere.

SOURCE: Data and further information can be found in International Telecommunication Union, RA 314 Series: Preferred Frequency Bands for Radio Astronomical Measurements, June 2003, http://www.itu.int/dms_pubrec/itu-r/rec/ra/R-REC-RA.314-10-200306-I!!PDF-E.pdf.