We present the results of a molecular survey of comet 67P/Churyumov-Gerasimenko undertaken with the Institut de RadioAstronomie Millimetrique (IRAM) 30-m radio telescope in November-December 2021, when it had its most favourable apparition in decades. Observations at IRAM 30-m during the 12-16 November period covered 8GHz bandwidth at 3mm, 16GHz at 2mm, and 60 GHz in the 1mm window domain. These were completed by snapshots at 1mm on 12-13 December and a short observation of the H_2_O line at 557GHz with the Odin sub-millimetre observatory on 17.0 November 2021, and with 18-cm observations of OH with the Nancay radio telescope. Less sensitive observations obtained at a previous perihelion passage on 18-22 September 2015 with IRAM and 9-12 November 2015 with Odin are also presented. The gas outflow velocity, outgassing pattern, and temperature have been accurately constrained by the observations. They are perfectly consistent with those measured in situ with the Rosetta/MIRO sub-millimetre instrument in 2015. In particular, the asymmetry of the line is well represented by a jet concentrating three-quarters of the outgassing in about pi steradians. We derived abundances relative to water for seven molecules and significant upper limits for approximately five others. The retrieved abundances were compared to those measured in situ at the previous perihelion with Rosetta. While those of HCN, CH_3_OH, and HNCO are comparable, 67P is found to be depleted in H_2_S and relatively normal in CS (H_2_S/CS_3_) in strong contradiction with the Rosetta/ROSINA mass spectrometer measurement of the H_2_S/CS_2_ (~100) abundance ratio. While the formaldehyde total abundance found with IRAM~30-m when assuming it to be mostly produced by a distributed source (Haser parent scale length ~8000km) is similar to the one derived by Rosetta/ROSINA, we find that the formaldehyde coming from the nucleus is one order of magnitude less abundant than measured in situ by Rosetta/ROSINA.
Cone search capability for table J/A+A/672/A170/list (List of fits spectra)
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