COBE, the Cosmic Background Explorer, was NASA’s first dedicated space telescope mission to study the cosmic microwave background in detail.
Launched on November 18, 1989, COBE measured the background radiation left from the early universe. Its instruments showed that the cosmic microwave background has an almost perfect blackbody spectrum, a major confirmation of Big Bang cosmology.
COBE also detected tiny temperature variations in that background radiation. These fluctuations represented early density differences that later grew into galaxies and large-scale cosmic structure. The results earned the 2006 Nobel Prize in Physics for John Mather and George Smoot.
WMAP and Planck later produced much more detailed maps, but they followed COBE’s foundational measurements. COBE is therefore not the same mission as the later satellites that refined the cosmic age and composition estimates.