eso9209 — Photo Release
1 July 1992
This photo shows Comet Grigg-Skjellerup, which will be visited by the Giotto spacecraft of the European Space Agency (ESA) on July 10, 1992
It was obtained by ESO astronomers Jesper Storm and George Meylan with the 3.5 metre ESO New Technology Telescope (NTT) at the La Silla observatory, in the evening of June 29, 1992. The comet was situated rather low in the western sky and the red-sensitive exposure lasted 1 minute.
On this date, the comet was about 220 million kilometres from the Earth and about 156 million kilometres from the Sun. It had developed a dust cloud (a 'coma') with an apparent diameter of 40 arcseconds, i.e. 40,000$ kilometres. This cloud of particles comes from the cometary nucleus, a large body of dust and ices (mostly frozen water). No coma features like 'jets' or 'shells' were visible yet. The magnitude of the comet was about 15, i.e.~close to the predicted brightness.
The accurate position of the comet on this photo was measured at the ESO Headquarters in Garching and transmitted to the Giotto Control Centre at ESOC, Darmstadt, Germany, in support of the spacecraft navigation.
The photo covers an area of 130 x 180 arcseconds; North is up and East is to the right.