Rosetta's optical navigation campaign has been a first for ESA and is a tremendous success.
If you missed the article published last week in the main ESA web site, the basic info is this: Optical navigation for Rosetta has used the spacecraft's Navigation Cameras (Nav Cams - there are two, 'A' & 'B') and the OSIRIS camera to image Steins (OSIRIS has two science cameras - the Narrow Angle camera has been used for the navigation campaign). These photos are then downloaded and interpreted to generate very precise determinations of Stein's location, and these results are then used to generate the necessary thruster burns to correct the spacecraft's course as it approaches.
On Tuesday, Sabine Kielbassa, on the Flight Dynamics team here at ESOC, sent along two more images with some interesting details. The optical navigation campaign has really shown just how good ESA's Flight Dynamics team are, and she was quick to mention that it's a team effort - together with her colleagues Trevor Morely, Mathias Lauer, and Vicente Companys, all of whom are supported by the extended FD team.
(larger-size images and captions after the jump) -- Daniel
Please find attached two Rosetta Nav Cam images taken from the navigation campaign.
Image 20080828T055308_1.jpg (click on either image for full size) was taken on 28.08.2008 at 05:53:08 UTC with Cam A using an integration time of 12 sec. It is approximately 700 x 650 pixels and is a cut of the original 1024 x 1024 image. Steins, with a magnitude of about 9 at that time, has been marked.
The bright star at upper left is Hipparcos No. 69701 with Mv = 4.07. This is the brightest object in the FOV (field of view); it is Iota Virginis in the constellation Virgo. After analysing this image, Steins was determined to be located at Right Ascension (RA) 213.894 deg, Declination (DE) -4.936 deg, as seen from Rosetta. The accuracy of this measurement is better than 1 millidegree and was achieved by matching 164 stars from the Hipparcos catalogue.
Image 20080825-29.gif is an animated GIF file, comprising five Nav Cam 'A' images taken daily between 25-29 August. The integration times of the images are decreasing, such that the apparent brightness of Steins remains constant, whereas the stars become fainter. The attitude profile was computed such that it was following Steins, so we see the stars moving relative to Steins.
Best regards, Sabine