The Rosetta orbiter - spacecraft design

Status: En route to Comet 67P/Churyumov-Gerasimenko

Objective: To rendezvous with Comet 67P/Churyumov-Gerasimenko where it will study the nucleus of the comet and its environment for nearly two years, and land a probe on its surface.

Mission
Rosetta is en route to Comet 67P/Churyumov-Gerasimenko, where it will make the most detailed study of a comet ever attempted. It will follow the comet on its journey through the inner Solar System, measuring the increase in activity as the icy surface is warmed up by the Sun.  The lander will focus on the composition and structure of the comet nucleus material. It will also drill more than 20cm into the subsurface to collect samples for inspection by the lander’s onboard laboratory.

What’s special?
Comets are considered the primitive building blocks of the Solar System, and likely helped ‘seed’ the Earth with water, and maybe even life. By studying the nature of the comet’s dust and gas, Rosetta will help scientists learn more about the role of comets in the evolution of the Solar System.

Rosetta will be the first mission ever to orbit a comet’s nucleus and land a probe on its surface.It will also be the first spacecraft to fly alongside a comet as it heads towards the inner Solar System, watching how a frozen comet is transformed by the warmth of the Sun.

Rosetta is the first space mission to journey beyond the main asteroid belt and rely solely on solar cells for power generation, rather than the traditional radio-isotope thermal generators. The new solar-cell technology used on the orbiter's two giant solar panels allows it to operate over 800 million kilometres from the Sun, where sunlight levels are only 4% of those on Earth.

Spacecraft
The main spacecraft measures 2.8 x 2.1 x 2.0 m with two 14 metre long solar panels. It carries instruments for remote sensing and radio science, and instruments to study the composition, mass distribution and dust flux of the comet’s nucleus, as well as the comet plasma environment and its interaction with the solar wind.

The orbiter’s 11 scientific instruments are accommodated on one side of the spacecraft, which will permanently face the comet during the operational phase of the mission.

Until its release, the 100kg Philae lander is carried on the opposite side of the orbiter to the large high-gain antenna dish. As Philae touches down on the comet, two harpoons will anchor it to the surface; the self-adjusting landing gear will ensure that it stays upright, even on a slope, and then the lander's feet will drill into the ground to secure it to the comet’s surface in the low gravity environment. Philae carries 9 scientific instruments, including a drill to sample subsurface material.

Journey
Rosetta launched on 2 March 2004 by an Ariane-5 G+ from Europe’s spaceport in Kourou, French Guiana. To place it on the required orbit to rendezvous with Comet 67P/ Churyumov-Gerasimenko it received four gravity assist manoeuvres: 3 from Earth (4 March 2005, 13 November 2007 and 13 November 2009) and 1 from Mars (25 February 2007).

Rosetta also passed by and imaged two asteroids: 2867 Steins on 5 September 2008 and 21 Lutetia on 10 July 2010.

The spacecraft entered deep space hibernation in July 2011 and will be woken up in January 2014, before rendezvousing with Comet 67P/ Churyumov-Gerasimenko in May 2014. It will follow the comet around the Sun and as it moves back out towards the orbit of Jupiter.

The lander, Philae, will be delivered to the comet’s surface in November 2014.

History
The International Rosetta Mission was approved in November 1993 by ESA's Science Programme Committee as the Planetary Cornerstone Mission in ESA's long-term space science programme. The mission goal was originally set for a rendezvous with comet 46 P/Wirtanen. After postponement of the initial launch a new target was set: Comet 67 P/Churyumov- Gerasimenko.

Rosetta gets its name from the famous Rosetta stone that led to the deciphering of Egyptian hieroglyphics almost 200 years ago. Similarly, scientists hope that Rosetta will unlock the mysteries of how the Solar System evolved.

Partnerships
The orbiter's scientific payload is provided by scientific consortia from institutes across Europe and the United States.

The lander is provided by a European consortium headed by the German Aerospace Research Institute (DLR). Other members of the consortium are ESA, CNES and institutes from Austria, Finland, France, Hungary, Ireland, Italy, and the United Kingdom.