Today’s CometWatch entry is an image taken by Rosetta’s NAVCAM on 30 September 2015, about 1488 km from the nucleus of Comet 67P/Churyumov-Gerasimenko. The image was taken a few hours after the spacecraft had reached the farthest point – 1500 km from the nucleus – on its far excursion to study the coma and plasma environment of 67P/C-G on a broader scale.
The scale is 127 m/pixel and the image measures 130 km across. The contrast was increased to reveal the comet’s activity. In this orientation, the small comet lobe is on the left and the large lobe on the right.
The last time Rosetta was at similar distances from the comet nucleus was in late July 2014, during the last few days of the ‘chasing’ phase, before the spacecraft arrived at 67P/C-G on 6 August 2014. For a qualitative comparison, take a look at these two CometWatch images from that period, taken on 30 July 2014, 1630 km from the nucleus, and on 31 July 2014, 1327 km from the nucleus.
At that time, the comet was about 540 million km from the Sun and only moderately active compared to current levels of activity. The comet is now just over 200 million km from the Sun, after passing through perihelion – the closest point to our star along its orbit – on 13 August.
Having reached the farthest point from the comet on the far excursion that started on 23 September, Rosetta is now approaching again, and will be back to about 500 km from the nucleus by 7 October.
The original 1024 x 1024 image of today’s CometWatch is provided below: