et al., 2007), ROSINA (Rosetta Orbiter Spectrometer for Ion and Neutral Analysis) (Balsiger et al., 2007), VIRTIS (Visible and Thermal Infrared Thermal Imaging Spectrometer) (Coradini et al., 2007), and OSIRIS (Optical, Spectroscopic, and Infrared Remote Imaging System) (Keller et al., 2007) instruments. Additional classification of several major dust regimes and their compositions were determined (G¨uttler et al., 2019) through the GIADA (Grain Impact Analyser and Dust Accumulator)

(Colangeli et al., 2007), MIDAS (Micro-Imaging Dust Analysis System) (Riedler et al., 2007), and COSIMA (Cometary Secondary Ion Mass Analyser) (Kissel et al., 2007) instruments. Owing to Rosetta’s close proximity to the comet, it was critically important to correlate its findings with those from other ground-based comet studies, which are constrained to observational scales ranging from 103-105 kilometres from the nucleus, far outside Rosetta’s domain. Extensive groundbased studies leading up to and during the mission were therefore executed to provide high-fidelity ground-truth measurements to better interpret the in-situ results collected by Rosetta (Snodgrass et al., 2017)[and references therein]. In this work, we build upon these previous ground-based studies with 12 follow-up epochs (see Figure 1) of integral field unit (IFU) observations from the Very Large Telescope (VLT) Multi-Unit Spectroscopic Explorer (MUSE) (Bacon et al., 2010) instrument during the most recent 67P apparition in 2021. One key advantage of our analysis is the far better viewing geometry of the 2021 apparition, which resulted in much higher angular resolution (subarcsecond) and closer geocentric distance that allowed for broad chemical species coverage. Therefore, this dataset is uniquely suited as the best comparison to the Rosetta mission, and present our results in the well-established context of post-Rosetta cometary science. It is important to note that the species, organics, and salts detected insitu by Rosetta cannot be directly detected using MUSE or other optical ground-based infrastructure. Despite this, we can observe photo-dissociated daughter products, C2, NH2, [OI], and CN, that optically fluoresce or emit light in the middle and outer coma, which are a product of parent gases released by the nucleus or coma particles. We therefore underscore the observational disconnect between the deep inner coma that Rosetta probed and the middle and outer coma that we observe, and that linking the two has been a longstanding problem in cometary sciences. Various studies have attempted to link the conditions measured by probes on and around comet nuclei to Earth-based coma observations in the optical regime (Crifo et al., 2004; Fulle et al., 2016). Although correlating in-situ results to ground based observations is non-trivial for most complex molecules, some photochemical pathways have been identified linking the two domains. Work by Fink et al. (1991) suggests that NH2 radicals are likely products of parent NH3 molecules directly sublimated from nucleic ices, however, additional sources could include sublimation of ammoniated salts within dust particles far from the nucleus (Dello Russo et al., 2016; Altwegg et al., 2020;

09 March 2022
15 May 2021

[Figure: Figure 1: Diagram depicting the orbits of the terrestrial planets, Jupiter, and comet 67P, as of the 2021 apparition. The region shaded red indicates the duration of the observational campaign using MUSE, with the red circles denoting the position of 67P for each observational epoch within the campaign and the blue circles representing the location of Earth for each epoch. The leftmost red circle corresponds to the earliest epoch, with the rightmost corresponding to the latest. The green diamond represents the 2021 perihelion.]