The Gaia spacecraft is composed of two sections: the Payload Module and the Service Module. The Payload Module is housed inside a protective dome and contains the two telescopes and the three science instruments. They are all mounted on a torus made of a ceramic material (silicon carbide).
GAIA is composed of three main parts; the astrometry instrument, the photometric instrument, and the radial-velocity spectrometer. The astrometry instrument is used to determine the angular positions of stars to better measure their distances and motions. The photometric instrument measures the luminosity of stars to help determine stellar properties such as temperature, mass, age, and what elements the stars are made up of. The radial-velocity spectrometer will determine the speed of galactic objects along the line of sight.
