Preparing the Rosetta deep-space operations

The International Rosetta Mission, cornerstone of the European Space Agency Scientific Programme, was launched on 2 March 2004 on its 10 years journey towards a rendezvous with comet Churyumov–Gerasimenko. Rosetta will reach the comet nucleus in summer 2014, orbit it for about 1.5 years down to distances of a few kilometres and deliver the lander Philae onto its surface. After its successful Asteroid fly-by in September 2008, Rosetta is coming back to Earth, for the last gravity acceleration towards its longest heliocentric orbit, up to a distance of 5.3 AU, never reached before by a solar generator-powered spacecraft. This revolution around the Sun will last several years, during which the spacecraft will have to be spun-up and put into hibernation mode, with most of the systems deactivated, to minimise power consumption. This paper presents the preparation and implementation of the deep space phase of the Rosetta mission. Differences between operations performed until now, at moderate distances to Earth and Sun, and the upcoming ones, involving distances up to 800 million km from the Sun and almost 1 billion km from Earth, are analysed and their impact on the operational concept described. The ground tools required in support of the operations are presented.