A kilopixel array of TES bolometers for ACT:: Development, testing, and first light

The Millimeter Bolometer Array Camera (MBAC) will be installed on the 6-meter Atacama Cosmology Telescope (ACT) in late 2007. For the first season of observations, MBAC will comprise a 145 GHz diffraction-limited, 1024-pixel, focal plane array of Transition Edge Sensor (TES) Bolometers. This will be the largest array of pop-up-detector bolometers ever fielded as well as one of the largest arrays of TES bolometers. We discuss the design specifications for the array and pre-assembly testing procedures for the cryogenic components. We present dark measurements of the TES bolometer properties of numerous 32-pixel columns that have been assembled into the first kilopixel array for ACT, as well as optical measurements made with our 256-pixel prototype array, including first light measurements on ACT.