Optical navigation campaign off to a good start                 19 Aug 2008


Rosetta's on-board cameras have successfully started to visually track
asteroid Steins in an optical navigation campaign. The images have been used
to calculate the asteroid's location and to optimise Rosetta's trajectory
for the upcoming fly-by of the asteroid on 5 September 2008.

The optical navigation campaign started on Monday 4 August, with Rosetta
still about 26 million kilometres from Steins. Unexpectedly, the two
navigation cameras (NAVCAM A & B) were able to detect the asteroid already
from day one of the campaign. Initially it was thought that in the early
phase of the campaign only the OSIRIS instrument would be able to observe
the asteroid.

The data gathered by both the NAVCAMs and the OSIRIS instrument have been
used to refine the model of the asteroid's orbit and to determine the
required delta-V of the trajectory control manoeuvre (TCM) that was
successfully performed on 14 August. The TCM has refined Rosetta's course
close to the desired fly-by conditions: 800 km distance from Steins at
closest approach on 5 September.

The optical navigation campaign will continue up to the fly-by, with several
slots set between now and 4 September for possible future manoeuvres, should
they be required.

For more details see: 
http://sci.esa.int/science-e/www/object/index.cfm?fobjectid=43271

--------------
European Space Agency Press Release 
http://sci.esa.int/science-e/www/object/index.cfm?fobjectid=43274