As part of the ongoing commissioning activities of Gaia, the satellite’s Sky Mapper has briefly been used in a special mode to image a patch of the sky close to the Galactic plane (below).
Detecting sources with Gaia's Sky Mapper.Credit: ESA
The job of the Sky Mapper is to detect stars entering Gaia’s field-of-view as the satellite slowly rotates. There’s one column of Sky Mapper CCD detectors for each of the two telescopes, in order to keep track of which star is coming from which telescope when the two beams are combined onto Gaia’s big camera.
In normal operations, the Sky Mapper is continuously operating, but the image data are not transmitted back to Earth like this. Instead, Gaia’s on-board computers analyse the data stream “on the fly” to detect the point sources, and to prepare small tracking “windows” which follow the stars as they move across the main astrometric CCDs.
Gaia focal planeCredit: ESA – A.Short
See the image above – or watch this movie – for a reminder of the layout of the Gaia focal plane and how the various parts of it work together.
The figure below shows the same Sky Mapper image, but this time also ...