WMAP — Wilkinson Microwave Anisotropy Probe (2001–2010)

WMAP refined measurements of the cosmic microwave background's temperature fluctuations to determine the universe is 13.77 billion years old, composed of 4.6% ordinary matter, 24% dark matter, and 71.4% dark energy. Operating from 2001 to 2010, NASA's probe mapped the CMB at 23-94 GHz frequencies with a resolution of 0.23 degrees, reducing primordial anisotropy uncertainties to ±0.1% in key parameters. Its seven-year data established the concordance cosmological model, outperforming #9 Gaia's galactic focus by providing the entire universe's early structure. WMAP's temperature-polarization cross-power spectrum confirmed inflationary predictions, showing a scalar spectral index of 0.963 ± 0.014. The mission measured baryon density to 4% precision using acoustic oscillation peak heights, cheaper than the typical rival satellite by using passive cooling at L2. WMAP's legacy includes constraining dark energy equation-of-state parameters to w = –1.0 ± 0.1, reshaping cosmology as the standard framework.