ESA: You have been working on the Rosetta mission for some years –why do you think it is so important?

Rita Schulz: When ESA's GIOTTO mission performed the first comet fly-by passing Halley's comet in 1986, I realised how much you can achieve in comet research when actually visiting the object with a spacecraft. GIOTTO has provided data that resulted in a quantum leap in our knowledge of comets at the time. Now Rosetta will not only fly past a comet within a few hours or days, but be in orbit around the comet nucleus for many months while the comet is moving along its orbit around the Sun. Rosetta will also send a lander onto the nucleus surface to obtain direct measurements. This will result in another quantum leap in knowledge not only in our understanding of comets, but also of how our solar system formed and evolved. Without a space rendezvous mission like Rosetta this would not be achievable.

ESA: What are the greatest challenges facing Rosetta?

Rita Schulz: Rosetta has already mastered a number of great challenges. The spacecraft has already been in space for more than eight years. It has mastered three Earth swing-bys, one Mars swing-by and two extremely successful asteroid fly-bys. The scientific results of the fly-bys at asteroids Steins and Lutetia in 2008 and 2010 have increased our knowledge of asteroids tremendously. Investigating asteroid Steins made it possible to characterise, for the first time, an E-type asteroid. The measurements obtained during the Lutetia fly-by revealed this asteroid to have undergone some internal heating early in its history, but not enough to melt completely. So it did not end up with a well-defined iron core, like the terrestrial planets and the Moon have.

Rosetta is now in hibernation and great challenges are still ahead. We have many "firsts" in this mission. For the first time ever, a spacecraft will (1) go into orbit around a comet nucleus, (2) land on the nucleus surface, and (3) accompany the comet along its orbit through its perihelion (point closest to the Sun) and out again towards the orbit of Mars and beyond. The scientific monitoring of the comet nucleus and its environment from the 11 instruments on board the Orbiter will be a challenge. Since the comet changes activity with time, certain observations cannot be repeated, hence they have to be perfect at the first attempt.

ESA: How will the Rosetta team cope with that?

Rita Schulz: The Rosetta teams in and outside ESA are fully engaged in the preparation of the comet phase. We are at full pace in preparing the spacecraft operations and the scientific measurements to be ready in time for the rendezvous in 2014.

ESA: What happens after Rosetta woke up from hibernation?

Rita Schulz: After wake up on 20 January 2014, we will have to first of all find the comet, navigate towards it, determinate the gravity potential and other general properties of the nucleus, and then navigate around it. The first Rendezvous manoeuvre will take place in May 2014. Then we will have to map the surface of the nucleus to find a safe place for our Lander Philae. This Global Mapping Phase will start in August 2014. In November 2014, Philae will land on the comet nucleus and execute a preprogrammed sequence of scientific measurements. After this the nominal scientific operations will start, with the Rosetta spacecraft staying in an elliptical orbit around the comet nucleus while the comet moves towards the Sun through perihelion and back into the outer solar system. The nominal end of the mission has been set for 31 December 2015.