WMAP

Explorer 80, Wilkinson Microwave Anisotropy Probe

Mission Profile

WMAP (Wilkinson Microwave Anisotropy Probe, Explorer 80) is a NASA cosmology satellite launched on 30 June 2001 aboard a Delta II to the Sun-Earth L2 Lagrange point, designed to measure the temperature fluctuations of the cosmic microwave background with unprecedented precision across the full sky. Its nine years of observations produced the definitive maps of the CMB that established the standard model of cosmology: a flat universe consisting of 4.6% ordinary matter, 24% dark matter, and 71.4% dark energy, with a precise age of 13.77 billion years. WMAP's constraints on cosmological parameters were so precise they ruled out entire classes of inflation models and established the spectral index of primordial density fluctuations. The mission's legacy fundamentally transformed cosmology from a data-starved to a precision science.