The Wilkinson Microwave Anisotropy Probe is a space-based instrument to measure the very small temperature fluctuations in the cosmic microwave background. The project to develop the Microwave Anisotropy Probe was started in 1994, based on a proposal by Charles L. Bennett. In 2003 it was renamed the Wilkinson Microwave Anisotropy Probe (WMAP) in honor of David T. Wilkinson, a pioneer in observing the cosmic microwave background, who played a major role in the design, construction, and early operation of WMAP. WMAP is the second medium-class Explorer mission to be launched by the National Aeronautics and Space Administration (NASA). Results from the first year of WMAP operation were released in February 2003.