Todd Barber, Cassini Lead Propulsion Engineer
|Ok, folks, some readers have expressed additional interest in the Optical Navigation (op-nav) images of Enceladus we took on Sunday night. They were posted within our raw image gallery , but I thought it would be a good idea to have them linked here. If nothing else, these images remind us of the scientific thrills to come in a few short days!|
|The Enceladus_no_zoom image (at left) shows the entire frame, with exposure times optimized for Enceladus. In this view, it is difficult to discern background stars.
One can zoom in on this image of Enceladus, and that’s seen in the image Enceladus_zoom (the next image down). These images, though intriguing and titillating, aren’t too useful for measuring the relative position of Enceladus.
|The next three images have a longer exposure time, in order to capture background stars. Enceladus_stars_bg_noID may not win any photo contests, but all the important stuff is there — a brightly lit crescent Enceladus, background stars, and even some typically seen cosmic ray hits. The stars seen in this image may seem very nondescript to you and me, but our op-nav experts know exactly which stars are which, thanks to excellent astrometry from orbiting telescopes like Hipparchos.|
|The picture labeled Enceladus_stars_bg_withID identifies a few background stars seen in the prior image.|
|Finally, Enceladus_stars_nobg_no/WithID just represents some quick-and-dirty image processing to remove the
artifact of horizontal banding seen in earlier images.
|The bottom line is our op-nav team helped nail Enceladus’ location within a few kilometers (or miles) with a
60-millisecond peek at Saturn’s orbiting ice ball. Not bad!