On Sunday 12 July 2015, OSIRIS, the scientific imaging system on board ESA’s spacecraft Rosetta, took a glance away from Comet 67P/Churyumov-Gerasimenko to the edge of our Solar System, towards Pluto.

Over five billion kilometres away, an exposure time of more than three hours, and sophisticated image processing, was necessary to detect Pluto in the images. Twenty images, each exposed for ten minutes, had to be stacked and carefully processed to reveal the tiny world. Pluto is thus the most distant body within the Solar System that Rosetta has ever looked at.

NASA’s space probe New Horizons made its historic flyby of this distant world today, passing within about 12500 km.

Being able to discern the 2370 km-wide body in OSIRIS images comes close to a small miracle, say the imaging team. “After all, OSIRIS is not a telescope, but a camera system designed to study Rosetta’s comet from up close," says OSIRIS Principal Investigator Holger Sierks from the Max Planck Institute for Solar System Research (MPS) in Germany.

"Apart from the huge distance there was another difficulty," says OSIRIS team member Dennis Bodewits from the University of Maryland who worked on the images. “Comet 67P and Rosetta are by now surrounded by a dense atmosphere of gas and dust. It’s like watching Pluto through a blizzard.”

The observation is particularly symbolic given that both Pluto and Comet 67P/C-G hail from the Kuiper Belt in the Outer Solar System. Comet 67P/C-G is now a Jupiter Family Comet and is currently in the inner Solar System, a month away from perihelion, the closest point to the Sun along its orbit. Pluto is a dwarf planet residing in the Kuiper Belt, and has an elliptical orbit around the Sun.

Rosetta has imaged a number of Solar System objects on en route to Comet 67P/C-G: Earth, Mars and the asteroids Steins and Lutetia during flybys, along with the more distant comet 9P/Tempel 1, asteroid P/2010 A2, and Saturn. “As in the case of Pluto, in comparison to observations from Earth such images often offer a unique and instructive viewing perspective,” says Sierks.

The Rosetta mission team sends its best wishes to the New Horizons team on today’s historic flyby!

About Rosetta
Rosetta is an ESA mission with contributions from its member states and NASA. Rosetta's Philae lander is provided by a consortium led by DLR, MPS, CNES and ASI.

About OSIRIS
The scientific imaging system OSIRIS was built by a consortium led by the Max Planck Institute for Solar System Research (Germany) in collaboration with CISAS, University of Padova (Italy), the Laboratoire d'Astrophysique de Marseille (France), the Instituto de Astrofísica de Andalucia, CSIC (Spain), the Scientific Support Office of the European Space Agency (The Netherlands), the Instituto Nacional de Técnica Aeroespacial (Spain), the Universidad Politéchnica de Madrid (Spain), the Department of Physics and Astronomy of Uppsala University (Sweden), and the Institute of Computer and Network Engineering of the TU Braunschweig (Germany). OSIRIS was financially supported by the national funding agencies of Germany (DLR), France (CNES), Italy (ASI), Spain (MEC), and Sweden (SNSB) and the ESA Technical Directorate.