The Satellite That Found 22 Photons and Changed Astronomy
On April 27, 1961, a Scout rocket lifted a 37-kilogram NASA satellite into orbit from Wallops Island carrying the first serious instrument for detecting cosmic gamma rays. Explorer 11 operated for seven months before its tape recorder failed. In that time it registered 22 gamma-ray photons - a pitiful number by modern standards, but enough to launch an entire branch of astronomy.