ABSTRACTUsing 4412 positional observations, we compute eight single apparition orbits in the period 1993–2017. The analysis of the residuals of the orbit’s fit shows their systematic deviations around perihelia. We assume that these deviations in positional observations are a result of the dust emissions from a restricted area of the nucleus, and that the ejected dust particles contain a certain amount of ice. Additional sublimation of ice from particles causes a gas-rich effect when the comet is approaching the Sun. Another effect of the jet motion of particles is a shift of the centre of brightness in the direction of ejection. Taking these effects into account, we estimate the size of the dust particles (2–10 cm) containing $80{{\ \rm per\ cent}}$ ice, dust velocities (1.8–2.6 m s−1), and the positions of active regions on the comet’s nucleus (cometocentric latitude from 55° to 74°). These estimates are based on the data for the residuals in the positional observations before the perihelia of the 1993, 2003, 2013 and 2017 apparitions.