Rosetta space probe

Rosetta is a European Space Agency-led unmanned space mission launched in 2004 intended to study the comet 67P/Churyumov-Gerasimenko. It consists of two main elements: the Rosetta space probe and the Philae lander. The probe is named after the Rosetta Stone, as it is hoped the mission will help unlock the secrets of how our solar system looked before planets formed. The lander is named after the Nile island Philae where an obelisk was found that helped decipher the Rosetta Stone.

Overview

During the 1986 apparition of the Comet Halley, a number of international space probes were sent to explore the cometary system, most prominent among them being ESA's highly successful Giotto. After the probes returned a treasure-trove of valuable scientific information it was becoming obvious that follow-ons were needed that would shed more light on the complex cometary composition and resolve the newly opened questions.

Both NASA and ESA started cooperatively developing new probes, the NASA led effort was the Comet Rendezvous Asteroid Flyby or CRAF mission, the follow-on Comet Nucleus Sample Return or CNSR mission was to be an ESA led effort, both missions were to share the common Mariner Mark II design, thus minimizing costs. In 1992, after NASA axed CRAF because of budgetary limitations, ESA decided on developing the spacecraft by themselves. By 1993 it was evident that the ambitious sample return mission was unfeasible with the existing ESA budget, so instead the mission was redesigned, with the final flight plan resembling the canceled CRAF mission, an asteroid flyby followed by a comet rendezvous with in-situ examination, including a lander.

It was set to be launched on January 12, 2003 to rendezvous with the comet 46P/Wirtanen in 2011. However this plan was abandoned after an Ariane 5 failure on December 11, 2002. A new plan was formed to target the comet 67P/Churyumov-Gerasimenko with launch on February 26, 2004 and rendezvous in 2014. After two cancelled launch attempts, Rosetta was launched on March 2, 2004 at 7:17 GMT. Besides the changes made to launch time and target, the mission profile remains almost identical. As before, the Rosetta craft will enter a very slow orbit around the comet and gradually slow down in preparation for releasing a lander that will make contact with the comet itself. The lander, named "Philae", will approach 67P/Churyumov-Gerasimenko at relative speed around 1 m/s and on contact with the surface, two harpoons will be fired into the comet to prevent the lander from bouncing off. Additional drills are used to further secure the lander on the comet.

Once attached to the comet, the lander will begin its science mission:

Characterisation of the nucleus
Determination of the chemical compounds present
Study of comet activities and developments over time

The exact surface layout of the comet is currently unknown and the orbiter has been built to map this before detaching the lander. It is anticipated that a suitable landing site can be found, although few specific details exist regarding the surface.

Mission timeline

This is the planned timeline for the mission after its launch:
- First Earth fly-by (March 2005)
- February 26 2007 Mars fly-by
- Second Earth fly-by (November 2007)
- September 5 2008 - flyby at asteroid 2867 Šteins
- Third Earth fly-by (November 2009)
- July 10 2010 - flyby at asteroid 21 Lutetia
- Deep-space hibernation (May 2011 - January 2014)
- Comet approach (January-May 2014)
- Comet mapping / Characterisation (August 2014)
- Landing on the comet (November 2014)
- Escorting the comet around the Sun (November 2014 - December 2015)

Major events and discoveries

2004

March 2 - ESA's Rosetta mission is successfully launched at 07:17 GMT (08:17 Central European Time). The launcher successfully placed its upper stage and payload into an eccentric coast orbit (200 x 4000 km). About two hours later, at 09:14 GMT, the upper stage ignited its own engine to reach an escape velocity in order to leave the Earth’s gravity field and enter heliocentric orbit. The Rosetta probe was released 18 minutes later. ESA’s Operations Centre (ESOC) in Darmstadt, Germany, established contact with the probe shortly after that.

May 10 - The first and most important deep space maneuver was successfully executed and brings the space craft on its correct course, with a reported inaccuracy of 0.05%.

2005

March 4 - Rosetta executed its first planned close flyby of Earth. The Moon and the Earth's magnetic field were used to test and calibrate the instruments on board of the spacecraft. The minimum altitude above the Earth's surface was about 1954.7 km at 22:09 UTC and images of the space probe passing by were captured by amateur astronomers.

July 4 - Imaging instruments on board observed the collision between the comet Tempel 1 and the impactor of the Deep Impact mission. ^*

Reference

"Comet chaser has new quarry", BBC News Online, March 7, 2003;

External links

Rosetta website
Rosetta Lander an article by Andrew J Ball, 1997.
gif animation showing images of Rosetta's March 4, 2005 fly-by of Earth.
Experiments German page with all onboard experiments.
Parallax demonstration with Rosetta fly-by

ESA probes | Comet/Asteroid missions