WMAP measured the cosmic microwave background with unprecedented precision after launching in 2001.
The Wilkinson Microwave Anisotropy Probe launched on June 30, 2001, and traveled to the Sun–Earth L2 point, about 1.5 million kilometers from Earth. From there, it mapped tiny temperature differences in the microwave glow left from the early universe.
WMAP’s observations refined estimates of the universe’s age, composition, geometry, and expansion history. Its data supported a universe about 13.7 billion years old in the mission’s final analysis and helped establish precise values for the proportions of ordinary matter, dark matter, and dark energy.
NASA’s COBE satellite had first detected and measured key large-scale properties of the cosmic microwave background, while WMAP produced much finer maps. The European Planck mission later improved several measurements further. WMAP completed science operations in 2010 and was decommissioned in 2010.