A multi-instrument analysis of 67P/Churyumov-Gerasimenko coma particles: COPS vs. GIADA
Authors: Pestoni Boris , Altwegg Kathrin , Della Corte Vincenzo , Longobardo Andrea , Müller Daniel , Rotundi Alessandra , Rubin Martin , Wampfler Susanne 
Published: September 2022

&lt;p&gt;The Rosetta mission of the European Space Agency has enabled a deep study of the nucleus and coma of comet 67P/Churyumov-Gerasimenko (hereafter 67P). Four instruments onboard the Rosetta spacecraft sensed coma particles ejected from the nucleus of 67P: the Grain Impact Analyzer and Dust Accumulator (GIADA; Della Corte et al. 2014), the COmetary Secondary Ion Mass Analyser (COSIMA; Kissel et al. 2007), the Micro-Imaging Dust Analysis System (MIDAS; Riedler et al. 2007), and the COmet Pressure Sensor (COPS; Balsiger et al. 2007). GIADA, COSIMA, and MIDAS were developed specifically for the study of cometary dust. COSIMA and MIDAS are sensitive only to refractories, GIADA is sensitive to refractories and (semi-)volatiles. On the other hand COPS is a gas density and pressure sensor that unexpectedly perceived the sublimating volatile fraction of cometary particles (Pestoni et al. 2021a,b). Since COPS measured a different component than the other three instruments, a comparison of the results of the latter is particularly worthy. In this study, we investigate correlations among the particle detections of COPS and GIADA.&lt;/p&gt;
&lt;p&gt;The two COPS gauges &amp;#8211; the nude gauge (hereafter NG) and the ram gauge (hereafter RG) &amp;#8211; detected 6.7e4 and 73 dust particles, respectively. GIADA subsystems led to the identification of 2110 compact particles, 3159 fluffy fragments arose by the fragmentation of 277 parent particles, and 4e-7 kilograms of mass coming from nanogram dust particles (Della Corte et al. 2019). It has been found that NG detections are correlated solely with GIADA parent particles, meaning that fluffy particles have both a volatile and a refractory part. Parent particles are fragmented by the spacecraft potential (Fulle et al. 2015). Consequently, the NG may not have observed intact parent particles, but one or more fluffy fragments reaching COPS remained unresolved within time resolution of the instrument. The diameters of equivalent water ice spheres calculated from the values of the density increases measured by the RG and the NG (60-850 nm assuming a density of 1 g cm&lt;sup&gt;&amp;#8722;3&lt;/sup&gt;; Pestoni et al. 2021a,b) are comparable to the sizes of the subunits of the fractal particles detected by MIDAS (52-183 nm; Mannel et al. 2019).&lt;/p&gt;
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