Monday

We present our results from the ground-based post-perihelion observing campaign of comet 67P/Churyumov–Gerasimenko, performed in parallel with the main phase of ESA's Rosetta mission at the comet. Polarimetric data was obtained with the FORS (FOcal Reducer/low dispersion Spectrograph) instrument at ESO's 8.2 m Unit 1 Antu of the Very Large Telescope (VLT) in Chile, and the ISIS (Intermediate dispersion Spectrograph and Imaging System) instrument at the 4.2 m William Herschel Telescope (WHT) on La Palma. We have sampled the phase angle range from 4 to 31 degrees with both the spectropolarimetric (PMOS) and direct polarimetric imaging modes (IPOL). Two filters were used at VLT for IPOL: R-special broadband filter and F485 narrowband filter. For PMOS, 300V grism was used. The filters at WHT were Sloan Gunn R and CO6 for IPOL. Additionally, a number of intensity maps were obtained with the ACAM (auxiliary-port camera) instrument at WHT using Sloan Gunn R, I, G, and T4450, T4550, T5700, T5770 and T6770 filters, as well as a spectroscopic map with the 2 arcsec slit on the V400 grism. Shape and variation of the comet's coma with wavelength and time is presented. Polarimetric properties are compared to the structure of the coma intensity features and discussed in terms of likely structure of the dust grains. The polarimetric phase curve is presented and the data discussed in context of 67P's place among other comets, as well as in view of recent Rosetta mission findings and other observations of the comet.