ESA Science & Technology - Gaia focal plane

The Gaia focal plane, shown above, will be the largest focal plane ever developed for space applications, featuring in total almost 1 billion pixels. The focal plane is common to both Gaia telescopes and is composed of five distinct areas:

1. The wave-front sensor (2 CCDs), used to measure the optical quality of each telescope, and the basic angle monitor (2 CCDs), used to monitor fluctuations in the basic angle;
2. The Sky Mappers: objects entering the fields of view first pass across the sky mappers (ASM1 or ASM2, each consisting of 7 CCDs). The sky mappers identify which telescope is viewing the object and are used to communicate details of the star transits to the subsequent CCDs;
3. The main Astrometric Field, devoted to astrometric measurements. The astrometric field of the focal plane will be sampled by 62 CCD detectors, each read out in time-delayed integration mode synchronised to the scanning motion of the satellite;
4. The Blue and Red Photometers, sampled by 14 CCDs serving Gaia's photometric instrument and providing low resolution spectrophotometric measurements for each object over the wavelength range 330-680 nm (blue) and 650-1050 nm (red);
5. The Radial Velocity Spectrograph, registering spectra of all objects brighter than about 17^th magnitude with 12 CCDs.