Vital stats   Herschel reflected in Planck mirror     Planck will offer vastly improved performance in measuring the Cosmic Microwave Background (CMB) radiation compared to balloon-borne and ground-based experiments and will exceed the performance of any previous space-based instruments of this kind. The spacecraft revolves about its Sun-pointing axis once per minute to stabilise its attitude. Planck will use this stabilisation spin to scan the sky, observing at least 95% of it through two separate observation periods in a span of 15 months.   The Planck spacecraft Dimensions 4.20 x 4.22 m (height x width) Mass 1.95 tonnes at launch Spacecraft Spin stabilised, 1 rpm Telescope mirror 1.9 x 1.5 m primary reflector Telescope mass 205 kg with focal plane unit Lifetime A minimum of 15 months, limited by degradation of cooling system Operational orbit Lissajous orbit at an average distance of 400 000 km from L2 Propulsion Hydrazine, 12 thrusters x 20 N each, 4 thrusters x 1 Newton each Solar arrays Flat, fixed triple-junction Gallium-Arsenide cell panels on rear of spacecraft   Solar array area: 13m2 Batteries 39 Ah lithium ion batteries Communication 3 x low gain antennae 1 x medium gain antenna         Last update: 2 March 2009  •  Planck: looking back at the dawn of time (http://www.esa.int/SPECIALS/Planck/index.html) Read more  •  Cosmic Microwave Background (CMB) radiation (http://www.esa.int/SPECIALS/Planck/SEMB3AR1VED_0.html)  •  Travelling back in time (http://www.esa.int/SPECIALS/Planck/SEMU3QS1VED_0.html)  •  Observations: Seeing in microwave wavelengths (http://www.esa.int/SPECIALS/Planck/SEM4B2T1VED_0.html)  •  So, how did everything start? (http://www.esa.int/esaSC/SEMC6TS1VED_index_0.html) In depth  •  Planck in depth (http://sci.esa.int/science-e/www/area/index.cfm?fareaid=17)  •  Planck spacecraft in depth (http://sci.esa.int/science-e/www/object/index.cfm?fobjectid=34729)