The First Rosetta Asteroid Fly-by
- Paper number
IAC-08.A3.5.1
- Author
Mr. Andrea Accomazzo, European Space Agency (ESA), Germany
- Coauthor
Dr. Paolo Ferri, European Space Agency (ESA), Germany
- Coauthor
Mr. Jose-Luis Pellon-Bailon, European Space Agency (ESA), Germany
- Coauthor
Ms. Armelle Hubault, Vega IT GmbH, Germany
- Coauthor
Mr. Sylvain Lodiot, European Space Agency (ESA), Germany
- Coauthor
Mr. Roberto Porta, Vega IT GmbH, Germany
- Year
2008
- Abstract
The International Rosetta Mission, a cornerstone mission of the European Space Agency Scientific Programme, was launched on 2nd March 2004 on its 10 years journey towards a rendezvous with comet Churyumov-Gerasimenko. Once reached the comet nucleus in summer 2014, Rosetta will orbit it for about 1.5 years down to distances of a few Kilometres and deliver a Lander, named Philae, onto its surface. In the long cruise to its target comet, Rosetta will cross twice the main asteroids belt, and in both occasions its trajectory is designed and controlled to fly-by an asteroid at close distance. On 5th September 2008 the first of the two asteroid fly-bys will be performed, with the spacecraft approaching asteroid 2867-Šteins at a minimum distance of about 800 Km, and a relative velocity of 8.6 Km/s. Šteins is an E-type asteroid with an estimated diameter of about 4.6 km. An observation by the Rosetta OSIRIS camera from 159 million Km distance in March 2006 indicates that Šteins has a rotation period of about 6 hours. The two asteroid fly-bys represent a secondary scientific objective for this mission. For the first time in its cruise, after several unplanned “bonus” scientific activities carried out in the past years, the Rosetta spacecraft will be operated to achieve a formal scientific target of the mission. From the flight dynamics point of view an asteroid fly-by poses different challenges compared to the swing-by manoeuvres already performed at Earth and Mars. The main problem is the large inaccuracy in the knowledge of the asteroid ephemerides as determined from ground observations. For this reason the Rosetta on-board navigation cameras will be utilised in the weeks before closest approach to improve the knowledge of the relative trajectory. This adds time criticality to the fly-by operations, with trajectory corrections planned as late as 12 hours before the event. In support of scientific observations also during the very short close fly-by phase, the spacecraft attitude is autonomously steered using the image of the target asteroid in the navigation cameras, trying to keep it as close as possible to the centre of the field of view. The few hours around closest approach require a unique spacecraft configuration and a series of time-critical operations which are specially designed for this phase. The main critical aspects of this activity are the rapid rotation on the spacecraft whilst tracking the asteroid; the abnormal thermal environment caused by the attitude profile and the solar aspect angle imposed by the fly-by geometry; the coordination of all subsystem and payload operations in this very short and one-off activity. All these aspects and the resulting operations strategy, timeline and procedures, require careful preparation and thorough validation work in the months before the fly-by. This paper presents the first Rosetta asteroid fly-by operations, identifying the critical aspects and describing the preparation, validation and execution phases. The lessons learned from this activity are analysed, and their application to the next Rosetta asteroid fly-by, and possibly to any other mission carrying out similar operations, are derived.
- Abstract document
- Manuscript document
IAC-08.A3.5.1.pdf (🔒 authorized access only).
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