Figure 1.

Observability of the comet, as seen from Earth, during the Rosetta mission. The observability of the comet from Earth is shown by hatched, cross-hatched and solid grey areas marking when the solar elongation is less than 50°, 30° and 15°, respectively. Perihelion (in August 2015) is marked by a vertical dashed line. At that time the comet was 43° from the Sun. Dash-dot vertical lines show the boundaries between the years 2014 and 2016. Upper panel: Solar elongation ϵ (solid line) and phase angle α (dashed line); middle panel: declination (Dec); lower panel: heliocentric r (solid line) and geocentric Δ (dashed line) distances.