DemoSat was a demonstration payload launched for the first flight of the Boeing (now United Launch Alliance / ULA) Delta IV Heavy. It was built to simulate the mass, center-of-gravity, frequency, and stiffness properties of an operational spacecraft. Three Corner Satellite (or 3CS, or 3CornerSat) consists of three student-built microsatellites flying in formation. 3CS’ primary mission objectives included demonstrating formation flying, providing stereoscopic imaging of cloud formations, and demonstrating distributed and autonomous operations. Only two spacecraft, Ralphie and Sparkie (developed by the University of Colorado at Boulder and Arizona State University), were launched initially. A third satellite, Petey, developed by New Mexico State University was not completed in time for launch. DemoSat and the two 3CS satellites were launched aboard the first flight of the Delta IV Heavy on December 21, 2004 from Cape Canaveral Air Force Station’s Space Launch Complex 37B (SLC-37B) located in Florida.