The Boomerang North America instrument : a balloon - borne bolometric radiometer optimized for measurements of cosmic background radiation anisotropies from 0 . 3 ◦ to 4 ◦

We describe the Boomerang North America (BNA) instrument, a balloonborne bolometric radiometer designed to map the Cosmic Microwave Background (CMB) radiation with 0.3 resolution over a significant portion of the sky. This receiver employs new technologies in bolometers, readout electronics, millimeterwave optics and filters, cryogenics, scan and attitude reconstruction. All these subsystems are described in detail in this paper. The system has been fully calibrated in flight using a variety of techniques which are described and compared. Using this system, we have obtained a measurement of the first peak in the CMB angular power spectrum in a single, few hour long balloon flight. The instrument described here was a prototype of the Boomerang Long Duration Balloon (BLDB) experiment. Dipartimento di Fisica, Universita’ La Sapienza, P.le A. Moro 2, 00185, Roma, Italy, e-mail: [email protected] Department of Physics, Queen Mary and Westfield College, Mile End Road, London, E1 4NS, U.K. Department of Physics, Math, and Astronomy, California Institute of Technology, Pasadena, CA, USA Jet Propulsion Lab, Pasadena, CA, USA IROE-CNR, Via Panciatichi 54, 50127 Firenze, Italy Ente Nazionale Energie Alternative, Frascati, Italy Dept. of Physics and Astronomy, University of Massachusets, Amherst, MA, USA Department of Astronomy, University of Toronto, Canada Istituto Nazionale di Geofisica, Roma, Italy Dept. of Physics, Univ. of California, Santa Barbara, CA, USA