ARCADE is a high altitude balloon payload designed to study the early universe. It measured the frequency spectrum of the Cosmic Microwave Background (CMB) at centimeter wavelengths, to search for signals from the first stars to form after the Big Bang. ARCADE's science goals were to observe the formation of structure from the first stars and galaxies, search for particle physics relics from the Big Bang, and understand the large-scale structure and energetics of our Galaxy. ARCADE flew in 2001, 2003, 2005 and 2006.