The carbon $^{12}$C/$^{13}$C ratio has been determined for several comets from the analysis of the C$_2$ Swan band and CN B-X system in the optical [@Manfroid2009; @BockeleMorvan2015 and references therein]. Some in situ measurements have also been obtained in comet 67P by the ROSINA mass spectrometer on-board the Rosetta spacecraft for C$_2$H$_4$, C$_2$H$_5$, CO [@Rubin2017] and CO$_2$ molecules [@Hassig2017]. All derived values are compatible with the terretrial ratio of 89, except for CO that could possibly be slightly enriched in $^{13}$C. The nitrogen $^{14}$N/$^{15}$N isotopic ratio was measured for the first time from high resolution spectra of the CN violet band in comets C/2000 WM1 (LINEAR) and C/1995 O1 (Hale-Bopp) and found to be enriched by a factor of two in $^{15}$N with respect to the Earth value [@Arpigny2003]. The same ratio was found later from sub-millimeter observations of HCN in comet 17P/Holmes during its outburst and archival data of C/1995 O1 (Hale-Bopp) [@BockeleMorvan2008]. It has also been recently possible to measure the $^{14}$N/$^{15}$N ratio in ammonia via the NH$_2$ radical [@Rousselot2014]. The values obtained are similar to the one found in HCN and CN, which was confirmed by subsequent works [@Shinnaka2014; @Rousselot2015; @Shinnaka2016a; @Shinnaka2016b; @Bin2018]. Recent measurements performed by 