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

E

International Astronomical Union Spectral Lines of Most Importance Above 1 THz

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. Spectral lines above 1 THz are listed in Table E.1. The suggested minimum bandwidths are Doppler-shifted frequencies corresponding to radial velocities of ±300 km/s, consistent with line radiation occurring in our Milky Way galaxy. Because of severe atmospheric attenuation (see Figure 2.6), most observations in this spectral region can only be conducted from space. Table E.1 notes those spectral transitions that fall within atmospheric “windows” that could be observed from the ground at a high, dry site. Following World Radiocommunication Conference (WRC) 2012, International Telecommunication Union (ITU) Radio Regulation 5.565 states that “all frequencies in the range 1000-3000 GHz may be used by both active and passive services.”

TABLE E.1 The Most Important Spectral Lines Above 1 THz

NOTE: Suggested minimum bands correspond to Doppler-shifted frequencies for ± 300 km/s (consistent with line radiation occurring in our Milky Way galaxy). Consolidated minimum bands reflect spectral regions where multiple molecular transitions result in overlapping recommend bandwidths; the minimum and maximum ranges reflect those of the lowest and highest frequencies for these spectral lines, respectively. G in the “Notes” column indicates that the line is observable from the ground under very good atmospheric condition.

SOURCE: Available at http://www.itu.int/dms_pubrec/itu-r/rec/ra/R-REC-RA.1860-0-201001-I!!PDF-E.pdf; IAU Resolution A.2 (1991, Buenos Aires; revised 2009, Rio de Janeiro); JPL Molecular Spectroscopy Database (http://spec.jpl.nasa.gov/); The Cologne Database for Molecular Spectroscopy (http://www.astro.uni-koeln.de/cdms/).