We present an extensive data set of ground-based observations and models of the dust environment of comet 67P/Churyumov-Gerasimenko covering a large portion of the orbital arc from about 4.5 au pre-perihelion through 3.0 au post-perihelion, acquired during the current orbit. In addition, we have also applied the model to a dust trail image acquired during this orbit, as well as to dust trail observations obtained during previous orbits, in both the visible and the infrared. The results of the Monte Carlo modelling of the dust tail and trail data are generally consistent with the in situ results reported so far by the Rosetta instruments Optical, Spectroscopic, and Infrared Remote Imaging System (OSIRIS) and Grain Impact Analyser and Dust Accumulator (GIADA). We found the comet nucleus already active at 4.5 au pre-perihelion, with a dust production rate increasing up to ~3000 kg s-1 some 20 d after perihelion passage. The dust size distribution at sizes smaller than r = 1 mm is linked to the nucleus seasons, being described by a power law of index -3.0 during the comet nucleus southern hemisphere winter but becoming considerably steeper, with values between -3.6 and -4.3, during the nucleus southern hemisphere summer, which includes perihelion passage (from about 1.7 au inbound to 2.4 au outbound). This agrees with the increase of the steepness of the dust size distribution found from GIADA measurements at perihelion showing a power index of -3.7. The size distribution at sizes larger than 1 mm for the current orbit is set to a power law of index -3.6, which is near the average value of insitu measurements by OSIRIS on large particles. However, in order to fit the trail data acquired during past orbits previous to the 2009 perihelion passage, a steeper power-law index of -4.1 has been set at those dates, in agreement with previous trail modelling. The particle sizes are set at a minimum of r = 10 ¿m, and a maximum size, which increases with decreasing heliocentric distance, in the 1-40 cm radius domain. The particle terminal velocities are found to be consistent with the in situ measurements as derived from the instrument GIADA on board Rosetta. © 2017 The Authors.

We are very grateful to an anonymous referee for her/his appropriate and constructive comments that helped to improve the paper considerably. This work was supported by contracts AYA2015-67152-R, AYA2015-71975-REDT and ESP2014-54032 from the Spanish Ministerio de Econom´ıa y Competitividad, and I/032/05/0 and I/024/12/0 from the Italian Space Agency (ASI). This paper is based on observations made with ESO telescopes at the La Silla Paranal Observatory under programmes IDs 592.C0924, 093.C-0593 and 094.C-0054. It is also based on observations collected at the Centro Astronomico Hispano-Alem ´ an (CAHA) at ´ Calar Alto, operated jointly by the Max-Planck Institut fuer Astronomie and the Instituto de Astrof´ısica de Andaluc´ıa (CSIC), and on data obtained at the Observatorio de Sierra Nevada, which is operated by the Instituto de Astrof´ısica de Andaluc´ıa (CSIC).