tokens: infrared yielding a water production rate in the range 3.2–3.0 × 10 28 molec. s −1 for the 7–11 September period, just before our IRAM observations. Faggi et al. (2019) , also from infrared observations of H 2 O, found water production rate in the range 2.6–2.8 × 10 28 molec. s −1 for the 8 September–7 October 2018 period. We thus assumed molec. s −1 at the time of IRAM observations ( Table 3 ). Comet 41P outgassing was monitored by several observatories during its 2017 approach, including the Solar Wind ANistropies (SWAN) instrument on the SOHO spacecraft (31 March to 20 April, Combi et al. 2019 ), TRAPPIST (11 March to 24 May for OH, Moulane et al. 2018 ) and with the Nançay radio telescope (4 March–5 June). The comet was not observed at Nançay at the time of the IRAM observations because of poor OH inversion. OH production rates of ≈ 1.1 × 10 28 and 0.6 × 10 28 molec. s −1 were obtained for the 28 March–3 April and 18–30 May, respectively. Most of the observations showed a plateau of activity ±20 days around perihelion with 4, 3 and 8 × 10 27 molec. s −1 respectively. We adopted a median value of molec. s −1 for the time of our observations. For comets 64P and 38P, around the time of our observations, water production rates were estimated from ground-based spectro-photometric observations of OH. D.G. Schleicher (priv. comm.) provided molec. s −1 for 64P on 16 December 2018. For comet 38P his values were molec. s −1 on 3 and 16 December 2018. We adopted water production rates of molec. s −1 for 64P and molec. s −1 for 38P, both to compute collision rates and determine molecular abundances. 64P and 38P were only observed in September and October at Nançay. 6 Production rates and abundances Line intensities have been converted to production rates using our time-dependent non-LTE code taking into account collisions with neutrals and electrons as well as solar radiative pumping via vibrational bands for HCN, CH 3 OH, CS, H 2 CO, CO, and CH 3 CN, as used in previous papers ( Biver et al. 2000 , 2006 , 2012 , 2014 , 2015 , 2016 ). Photolysis constants are also from previous papers and detailed in Biver et al. (2021) . Production rates or upper limits are provided in Table 4 . For species with multiple lines observed at the same time, the weighted average is provided. 6.1 Relative abundances Abundances relative to water were computed using the average water production rates provided in Table 3 . For 41P we assumed a lower water production rate (0.3 × 10 28 molec. s −1 ) for the second day (1.0 May 2017) because HCN and CH 3 OH showed a significant decrease in production rate and Moulane et al. (2018) also found a decrease in the water production rate between 26.1 April and the 28 April–3 May period. For 38P, abundances relative to water assume molec. s −1 . Although no line is detected with a signal-to-noise larger than 2, the combined signal of the 13 strongest methanol lines at 165–170 GHz and 242 GHz yields a formal signal-to-noise of 3.5 and a
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