Rosetta nicely lined up for Earth approach
The first (and most important) trajectory correction manoeuvre (TCM) executed last Thursday was extremely accurate, and Rosetta is nicely lined up for the approach to Earth. After a preliminary analysis, Trevor Morley, lead Rosetta flight dynamics specialist here at ESOC, has told us that closest approach to Earth is now expected at 07:45:40.1 UTC (08:45:40.1 CET) on 13 November.
Last week's TCM burn lasted 86 seconds and provided an 8.8 cm/second change in orbital velocity - and the thruster performance was very good.
Bonus: Nice chart showing projection of Rosetta's approach trajectory included in this post.
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"The manoeuvre was very close to the predicted and required amount. We will continue to analyse the results to determine whether we will need any additional manoeuvres," said Trevor in an email this morning. Trevor is the lead ESA flight dynamics specialist working on Rosetta.
To analyse the performance, the team used data from a number of sources, including:
• Telemetry radioed down by Rosetta, including star tracker data and parameters related to fuel usage and thruster operation.
• Doppler and ranging data received from the ESA and NASA ground stations that have been following Rosetta over the past few days.
We were told that, based on the flight dynamics team analysis so far, Rosetta's thrusters over-performed slightly, in the range of 0.06-0.07%. As a result, the team have updated the predicted time of closest approach, or perigee passage, on 13 November to 07:45:40.1 UTC (08:45:40 CET) with a 3-sigma uncertainty of 1.0 seconds. This estimate will be updated in the next few days. ("3-sigma" refers to how the engineers and scientists express uncertainty, and is a meaure of how confident a result can be.)
If needed, Rosetta has slots for additional TCMs at 1 week, 1 day and 6 hours prior to closest approach.
The tracking stations following Rosetta in the past few days include ESA's 35m DSA 1 station at New Norcia, Australia, and NASA's DSN antennas at Goldstone, California and at Robledo, near Madrid. -- Daniel & Amruta
Image
View of Rosetta's approach trajectory to Earth for next month's ESB3. This view is from above the Earth looking down on the ecliptic plane - the plane of Earth's equator, more or less (click for larger version). Note that the trajectory has changed slightly since when this projection was made, but it's still a good indication.
Credits: ESA Flight Dynamics
La sonde Rosetta en orbite terrestre.
Cette animation montre le principe de l'assistance gravitationnelle. La courbe rouge représente l'évolution de la vitesse de la sonde dans le temps.

La sonde de l'agence spatiale européenne Rosetta, lancée en mars 2004, effectuera son dernier survol de la Terre (''earth swing-by'', abrégé ESB) le vendredi 13 novembre à 07 h 45 UTC, a annoncé l'ESA.

Ce dernier passage doit lui permettre d'acquérir de la vitesse, selon la méthode de l'assistance gravitationnelle, avant de partir dans l'espace lointain vers la comète 67P/Churyumov-Gerasimenko, qu'elle devrait atteindre en 2014.

Par le passé, deux autres survols ont étés effectués : un en mai 2005 puis un le 13 novembre 2007.

Rosetta a été baptisée d'après la fameuse pierre de Rosette, qui permit il y a près de 200 ans de déchiffrer les hiéroglyphes égyptiens. En 2008, la sonde a survolé l'astéroïde (2867) Šteins et devrait survoler en 2010 (21) Lutèce. L'objectif principal de la mission, dont la fin est prévue pour décembre 2015, est l'étude de la comète 67P/Churyumov-Gerasimenko, sur laquelle la sonde déposera l'atterisseur Philae.