Flight model of the Planck spacecraft. The satellite size is about 4.2 × 4.2 m, and its mass at launch was 1950 kg. Planck was launched on 14 May 2009, and operated for 4.4 years from a Lissajous orbit around the Lagrangian point L2 of the Sun–Earth system. Shown are the approximate temperatures of different critical parts of the satellite during nominal operation in space (see Planck Collaboration II 2011).