WMAP (Wilkinson Microwave Anisotropy Probe) spacecraft. Computer artwork of the WMPAP spacecraft travelling towards the second Lagrangian point (L2), situated about 1.5 million kilometres from Earth (blue sphere) in the opposite direction to the Sun (sphere at far left). It has used the Moon (above right of Earth) as a slingshot to gain velocity for the trip. Once at the L2 the WMAP will study the Cosmic Microwave Background, the radiation left over from the Big Bang. WMAP was launched on 30th June 2001 and commenced its sky survey on 11th February 2003.