Telescopes
Space telescope Gaia actually consisted of two telescopes. Its telescopes contained ten mirrors of different shapes and sizes to collect, focus and direct light into Gaia’s science instruments for detection.
Each telescope contained a large primary mirror with a collecting area of about 0.7 m^2. These had a rectangular shape to make the most efficient use of the limited space inside the spacecraft. Although these are small mirrors compared with many ground-based telescopes, Gaia had the supreme advantage of observing from space, where there is no atmospheric disturbance to blur the images.
Gaia was just 3.5 m across (excluding the sunshade, which is about 10 m across). Three curved mirrors and three flat mirrors focus and repeatedly fold the light over a total distance of 35 m before it reaches the detectors.
Each of Gaia’s three science instruments used a set of digital detectors – charged coupled devices (CCDs) – to record the starlight falling onto them. Together Gaia’s CCDs made the largest focal plane ever flown to space, a total of one billion pixels covering an area of 0.38 m^2.