Gaia in the UK

Taking the Galactic Census

Source Environment Analysis

Source Environment Analysis presentation is based on "Source Environment Analysis 101" animation by Diana Harrison, Institute of Astronomy, Cambridge.

The Source Environment Analysis is the software used for detecting faint companions to sources measured by Gaia. This can improve the interpretation of any sources affected in later data reductions. The presentation shows the main steps in the Source Environment Analysis process, taken when Sky Mapper detects a bright star with faint neighbouring objects (the Sky Mapper, also often referred to as the Star Mapper, consists of two strips of CCDs, one for each field of view; its primary use is the detection of sources and measuring the rotation rates of the satellite):

1. Star Mapper detects the bright star.

2. The read-out from the CCD in a window around the star is saved.

3. Detection data is used to read out from the Astrometric Field CCDs higher resolution, but smaller window around the star.

4. The data is prepared for sending back to Earth. There are many stars and limited bandwidth - the data must be compressed. For all but the very brightest stars the windows are binned: 216 pixels becomes 18. The Star Mapper windows must also be binned.

5. Later Gaia will see the star again, but at this later time the CCD will be at a different angle with respect to the star. On average Gaia will see each star 85 times.  We can combine windows from the same star to try to work out where the light is coming from in order to discover the bright star’s faint neighbours.


Page last updated: 23 December 2013