Gaia M2 mirror
The Gaia payload is characterised by a dual telescope with a common structure and thanks to the M4 mirrors, they are sharing the same focal plane whereas they are imaging two separate fields of view (see related images). Each telescope is based on a three mirror anastigmatic design with three flat-folding mirrors, the two viewing directions separated by a 106.5 degrees basic angle.
The three mirror anastigmatic telescope is defined by M1, M2 and M3. The M2 mirror pictured here is a rectangular off-axis convex mirror with dimensions 34.5 cm × 15.0 cm. The M2 mirror lightweighted blank is made of Sintered Silicon Carbide (SiC) and it is coated with a CVD SiC coating prior polishing. The polished surface then receives a protected silver reflective coating.