2002-2003 Science Planning Summary

Aeronomy & Astrophysics

Dr. Vladimir Papitashvili
Program Manager

AO-378-O

NSF/OPP 00-91840
Station: South Pole Station
RPSC POC: Paul Sullivan
Research Site(s): South Pole Station

ACBAR (Arcminute Cosmology Bolometer Array)
Dr. William L. Holzapfel
University of California Berkeley
Physics
swlh@cfpa.berkeley.edu
http://cosmology.berkeley.edu/~swlh/research/acbar.html
Dr. John Ruhl
University of California, Santa Barbara
Department of Physics

Deploying Team Members: William L Holzapfel
Research Objectives: Advances in detector technology are enabling a revolution in cosmology. Arrays of bolometric detectors on the ground have recently been used to image large regions of the cosmic microwave background (CMB) sky from balloons and are detecting luminous dusty galaxies at high redshift. The arcminute cosmology bolometer array receiver (ACBAR) is a 16-element, 250-micro-Kelvin detector system that was deployed at the South Pole in November 2000 and is designed to be used with the Viper telescope there. ACBAR will image the sky in four bands, filling an important niche in angular-scale and frequency coverage between existing millimeter-wave balloon-borne and ground-based instruments. These four frequency bands were chosen to take full advantage of the excellent millimeter (mm) and submillimeter atmospheric windows available for observations from the South Pole.

ACBAR is designed to probe the universe in two distinct ways: First, the measurement of small angular-scale structure in the CMB will complement the large angular scales probed by various satellites and balloon-borne instruments, leading to improved constraints on cosmological models. Second, the imaging and discovery of galaxy clusters with the Sunyaev-Zel’dovich Effect (SZE) will provide a wealth of new cosmological information. ACBAR’s broad frequency and angular-scale coverage enable enormous leaps forward in both of these directions. The receiver also serves as a test bed for the detector and optics technology that will eventually fly on the European Space Agency’s Planck satellite in 2007.

With this combination of sensitive detectors, high-angular resolution, and broad frequency coverage, ACBAR will advance cosmology research on several fronts. Observations of the CMB provide a glimpse of the universe at the time when it was only about 300,000 years old. Only recently have technological advances made observations of the SZE possible. To separate the thermal and kinematic components of the SZE, observations must be made at several mm-wavelength frequencies. Other experiments are producing detections of the SZE in x-ray-discovered distant clusters. ACBAR will significantly advance these efforts. This second season of observation will see the analysis and publishing of the results of two previous years of observation.


Field Season Overview:
The ACBAR receiver shares time with other instruments on the Viper telescope at the South Pole. Project team members will install and remove the instrument twice to accommodate the share schedule. They will also prepare the receiver for winter observations, calibrate the previous winter's observations and install minor upgrades.

During the second half of the field season, new observations will begin. During the austral winter, the station science technician monitors the equipment and performs routine maintenance.