The ARCADE 2 Instrument

TL;DR

ARCADE 2 is a balloon-borne radiometer designed to precisely measure the cosmic microwave background and diffuse emissions across six frequencies, employing innovative cryogenic and calibration techniques to minimize systematic errors.

Contribution

This paper introduces the ARCADE 2 instrument's design, including its cryogenic open aperture and double-nulled radiometric approach, enhancing measurement accuracy for cosmic background studies.

Findings

Successful measurement of CMB temperature at multiple frequencies

Effective reduction of systematic errors through novel thermal design

Demonstrated stable performance during flights

Abstract

The second generation Absolute Radiometer for Cosmology, Astrophysics, and Diffuse Emission (ARCADE 2) instrument is a balloon-borne experiment to measure the radiometric temperature of the cosmic microwave background and Galactic and extra-Galactic emission at six frequencies from 3 to 90 GHz. ARCADE 2 utilizes a double-nulled design where emission from the sky is compared to that from an external cryogenic full-aperture blackbody calibrator by cryogenic switching radiometers containing internal blackbody reference loads. In order to further minimize sources of systematic error, ARCADE 2 features a cold fully open aperture with all radiometrically active components maintained at near 2.7 K without windows or other warm objects, achieved through a novel thermal design. We discuss the design and performance of the ARCADE 2 instrument in its 2005 and 2006 flights.