2. Source Environment Analysis 101

4. Imagine 1 bright star with faint neighbouring stars

8. Star Mapper detects the bright star

9. saves the read-out from the CCD in a window around the star

11. Detection data used to read out from the Astrometric Field CCDs

12. Higher resolution, but smaller window around the star

13. However …

15. We have to get the data back to Earth

16. there are
many stars

17. and limited
bandwidth

18. the data must be compressed

20. For all but the very brightest stars the windows are binned

21. 216 pixels
becomes 18

23. The Star Mapper windows

25. must also be binned

29. Later Gaia will see the star again

31. at this later time the CCD will be at a different angle

32. with respect to the star

34. on average Gaia will see

36. each star 85 times

38. We can combine windows from the same star

40. to try, to work out

42. where the light is coming from

49. In order to discover the bright star’s faint neighbours

50. In order to discover the bright star’s faint neighbours