BICEP3

BICEP3
NASA/JPL-Caltech · Attribution · source
Name	BICEP3
Type	Telescope
Site	South Pole Station
Built	2014–2015
Operator	Keck Array and BICEP Array team
Affiliation	Caltech, Harvard, MIT, Stanford, University of Chicago

BICEP3 is a ground-based microwave polarimeter designed to measure the polarization of the cosmic microwave background radiation. Located at the South Pole Station and operated by a consortium including California Institute of Technology, Harvard University, Massachusetts Institute of Technology, Stanford University, and the University of Chicago, it targets the degree-scale B-mode signal associated with primordial gravitational waves and lensing. BICEP3 follows earlier instruments such as the BICEP2 and Keck Array and complements satellite missions like Planck and balloon experiments such as BOOMERanG.

Overview

BICEP3 is part of a sequence of experiments including BICEP1, BICEP2, and the Keck Array that build on technology from the South Pole Telescope and the Atacama Cosmology Telescope. Funding and oversight involved agencies and institutions such as the National Science Foundation, the NASA research programs, the Kavli Foundation, and university grants from Caltech, Harvard, MIT, and Stanford University. The instrument contributes to broader efforts alongside missions including WMAP, Planck, SPTpol, and ACTPol to characterize the polarization patterns imprinted by inflationary physics predicted in scenarios associated with Alan Guth and Andrei Linde. The project interacts with analysis frameworks used by teams from Perimeter Institute, Max Planck Institute for Astrophysics, CERN, and the Kavli Institute for Cosmological Physics.

Instrumentation and Design

BICEP3’s optical design draws on refracting telescopes used by predecessors and contemporaries like BICEP2 and the Keck Array, adopting cold optics and anti-reflection coatings informed by developments at JPL and NIST. The focal plane hosts thousands of transition-edge sensor bolometers similar to those developed for instruments at SRON and Cardiff University and patterned after detectors used in EBEX and POLARBEAR. Readout employs time-division multiplexing and SQUID amplifiers pioneered at Lawrence Berkeley National Laboratory and Brookhaven National Laboratory, integrating cryogenic systems from collaborations with South Pole IceCube Laboratory teams. The telescope mount and pointing hardware derive from mechanical designs used at DASI and QUaD and incorporate servo systems like those at ALMA and VLA. Optical filters and half-wave plates use materials developed in partnership with University of California, Berkeley, Princeton University, and University of Pennsylvania laboratories.

Observations and Survey Strategy

Observations are conducted at the Amundsen–Scott South Pole Station during austral winters, leveraging the dry, stable atmosphere exploited by South Pole Telescope and DASI. The survey strategy focuses on deep integrations over low-foreground regions near southern celestial fields also observed by Planck, WMAP, and the Keck Array, enabling cross-correlation with data from SPTpol, ACTPol, and Polarbear. Nightly scans use elevation nods and boresight rotations analogous to methods used by BICEP2 and Keck Array to mitigate instrumental systematics characterized by teams at Caltech and Harvard–Smithsonian Center for Astrophysics. Coordination with logistics entities such as the United States Antarctic Program and Raytheon Polar Services supported seasonal deployment and maintenance.

Data Processing and Analysis

Raw timestream data processing follows pipelines influenced by software and algorithms developed for Planck and WMAP, with mapmaking and component separation techniques comparable to those used by the Planck Collaboration and the SPT collaboration. Analyses employ maximum-likelihood estimators and Monte Carlo simulations similar to methods at Perimeter Institute and Institute for Advanced Study to quantify uncertainties and covariance matrices used by groups at Princeton University and MIT. Foreground modeling leverages templates and spectral indices constrained by studies from Planck, WMAP, IRAS, and Herschel teams to separate Galactic dust and synchrotron emissions studied by Harvard–Smithsonian Center for Astrophysics and Rutgers University. Systematics tests follow validation procedures developed at Caltech, Stanford, and University of Chicago and cross-checks use independent analyses from Max Planck Institute for Astrophysics and Lawrence Berkeley National Laboratory collaborators.

Scientific Results and Implications

BICEP3’s results inform constraints on the tensor-to-scalar ratio r, complementing limits provided by Planck, WMAP, and the Keck Array, and contribute to joint analyses with teams from SPTpol, ACTPol, and the Planck Collaboration. Findings impact models of cosmic inflation associated with theorists like Alan Guth, Andrei Linde, and Paul Steinhardt and intersect theoretical frameworks developed at Perimeter Institute, Institute for Advanced Study, and Kavli Institute for Cosmological Physics. Measurements of B-mode polarization have implications for primordial gravitational waves searched for in complementary experiments such as LIGO, VIRGO, and proposed missions like LISA. BICEP3 also refines knowledge of Galactic foregrounds with relevance to astrophysical studies performed by Herschel, Spitzer, and IRAS research teams, aiding cosmological parameter estimation efforts carried out by groups at Caltech, Harvard, and MIT.

Collaborations and Logistics

The BICEP3 team comprises scientists and engineers affiliated with institutions including California Institute of Technology, Harvard University, Massachusetts Institute of Technology, Stanford University, University of Chicago, University of British Columbia, University of Minnesota, Cardiff University, and McGill University. Logistical support was provided by agencies and contractors such as the United States Antarctic Program, National Science Foundation, and Raytheon Polar Services Company, with coordination alongside facilities like the South Pole Station and Antarctic research programs connected to British Antarctic Survey and Australian Antarctic Division. BICEP3 fits within broader collaborations that include data-sharing and joint publications with the Keck Array team, the Planck Collaboration, the SPT collaboration, and the ACT collaboration.

Category:Cosmic microwave background experiments Category:Telescopes in Antarctica