View source for BICEP and Keck Array

{{Short description|Series of cosmic microwave background experiments at the South Pole}}
{{Infobox telescope}}
'''BICEP''' ('''Background Imaging of Cosmic Extragalactic Polarization''') and the '''Keck Array''' are a series of [[cosmic microwave background]] (CMB) [[List of cosmic microwave background experiments|experiments]]. They aim to measure the [[Polarization in astronomy|polarization]] of the CMB; in particular, measuring the [[B-modes|''B''-mode]] of the CMB. The experiments have had five generations of instrumentation, consisting of '''BICEP1''' (or just '''BICEP'''), '''BICEP2''', the '''Keck Array''', '''BICEP3''', and the '''BICEP Array'''. The Keck Array started observations in 2012 and BICEP3 has been fully operational since May 2016, with the BICEP Array beginning installation in 2017/18.

==Purpose and collaboration==
[[File:History of the Universe.svg|thumb|left|200px|[[Gravitational waves]] may arise from [[Inflation (cosmology)|inflation]], a phase of [[accelerated expansion]] after the [[Big Bang]].<ref name="BICEP2-2014" /><ref name="NASA-20140317" /><ref name="NYT-20140317" /><ref name="NYT-20140324" />]]
The purpose of the BICEP experiment is to measure the polarization of the cosmic microwave background.<ref name="bicep_caltech" /> Specifically, it aims to measure the ''B''-modes ([[Curl (mathematics)|curl]] component) of the [[Polarization in astronomy|polarization]] of the CMB.<ref name="CaltechPressRelease" /> BICEP operates from [[Antarctica]], at the [[Amundsen–Scott South Pole Station]].<ref name="bicep_caltech" /> All three instruments have mapped the same part of the sky, around the [[south celestial pole]].<ref name="bicep_caltech" /><ref name="keck_instrument" />

The institutions involved in the various instruments are [[Caltech]], [[Cardiff University]], [[University of Chicago]], [[Harvard-Smithsonian Center for Astrophysics|Center for Astrophysics {{!}} Harvard & Smithsonian]], [[Jet Propulsion Laboratory]], [[CEA-Leti: Laboratoire d'électronique des technologies de l'information|CEA Grenoble (FR)]], [[University of Minnesota]] and [[Stanford University]] (all experiments); [[UC San Diego]] (BICEP1 and 2); [[National Institute of Standards and Technology]] (NIST), [[University of British Columbia]] and [[University of Toronto]] (BICEP2, Keck Array and BICEP3); and [[Case Western Reserve University]] (Keck Array).<ref name="CaltechPressRelease" /><ref name="bicep1_collaboration" /><ref name="bicep2_collaboration" /><ref name="keck_collaboration" /><ref name="bicep3_collaboration" />

The series of experiments began at the [[California Institute of Technology]] in 2002. In collaboration with the Jet Propulsion Laboratory, physicists [[Andrew Lange]], Jamie Bock, [[Brian Keating]], and William Holzapfel began the construction of the BICEP1 telescope which deployed to the [[Amundsen-Scott South Pole Station]] in 2005 for a three-season observing run.<ref name="2002NSFgrant" /> Immediately after deployment of BICEP1, the team, which now included Caltech postdoctoral fellows John Kovac and Chao-Lin Kuo, among others, began work on BICEP2. The telescope remained the same, but new detectors were inserted into BICEP2 using a completely different technology: a printed circuit board on the focal plane that could filter, process, image, and measure radiation from the cosmic microwave background. BICEP2 was deployed to the [[South Pole]] in 2009 to begin its three-season observing run which yielded the detection of B-mode polarization in the cosmic microwave background.
{{Clear}}

==BICEP1==
The first BICEP instrument (known during development as the "Robinson gravitational wave background telescope") observed the sky at 100 and 150&nbsp;GHz (3&nbsp;mm and 2&nbsp;mm wavelength) with an [[angular resolution]] of 1.0 and 0.7 [[degree (angle)|degrees]]. It had an array of 98 detectors (50 at 100&nbsp;GHz and 48 at 150&nbsp;GHz), which were sensitive to the [[Polarization (waves)|polarisation]] of the CMB.<ref name="bicep_caltech" /> A pair of detectors constitutes one polarization-sensitive pixel. The instrument, a prototype for future instruments, was first described in Keating et al. 2003<ref>
{{cite book
 |last1=Keating |first1=Brian
 |display-authors=et al
 |date=2003
 |chapter=BICEP: a large angular scale CMB polarimeter
 |chapter-url=https://authors.library.caltech.edu/92297/1/284.pdf
 |editor1-last=Fineschi |editor1-first=Silvano
 |title=Polarimetry in Astronomy
 |series=[[Proceedings of SPIE]]
 |volume= 4843|pages=284–295
 |bibcode=2003SPIE.4843..284K
 |doi=10.1117/12.459274
 |s2cid=122838031
 |url=<!-- -->
 }}</ref> and started observing in January 2006<ref name="CaltechPressRelease" /> and ran until the end of 2008.<ref name="bicep_caltech" />
<!-- To be specific, the frequencies were 97.7±24.4 and 151.8±42.9 GHz -->

==BICEP2==
{{multiple image
| align     = right
| direction = vertical
| image1    =
| width1    = 200
| alt1      =
| caption1  = BICEP instrument at the South Pole
| image2    = South pole spt dsl.jpg
| width2    = 200
| alt2      =
| caption2  = BICEP2 telescope near [[South Pole Telescope]]
| image3    = Antarctica (11235782635).jpg
| width3    = 200
| alt3      =
| caption3  = Keck Array at Martin A. Pomerantz Observatory
}}
The second-generation instrument was BICEP2.<ref name="bicep2" /> Featuring a greatly improved focal-plane [[transition edge sensor]] (TES) bolometer array of 512 sensors (256 pixels) operating at 150&nbsp;GHz, this 26&nbsp;cm aperture telescope replaced the BICEP1 instrument, and observed from 2010 to 2012.<ref name="BICEP2_2014_1" /><ref name="BICEP2_2014_2" />

Reports stated in March 2014 that BICEP2 had detected ''B''-modes from [[gravitational waves]] in the [[early universe]] (called [[primordial gravitational wave]]s), a result reported by the four co-principal investigators of BICEP2: [[John M. Kovac]] of the [[Harvard-Smithsonian Center for Astrophysics|Center for Astrophysics {{!}} Harvard & Smithsonian]]; Chao-Lin Kuo of [[Stanford University]]; Jamie Bock of the [[California Institute of Technology]]; and Clem Pryke of the [[University of Minnesota]].

An announcement was made on 17 March 2014 from the [[Harvard-Smithsonian Center for Astrophysics|Center for Astrophysics {{!}} Harvard & Smithsonian]].<ref name="BICEP2-2014" /><ref name="NASA-20140317" /><ref name="NYT-20140317" /><ref name="NYT-20140324" /><ref name="bmodes" /> The reported detection was of B-modes at the level of {{nowrap|1=''r'' = {{val|0.20|+0.07|-0.05}}}}, disfavouring the [[null hypothesis]] ({{nowrap|1=''r'' = 0}}) at the level of 7 [[Standard deviation|sigma]] (5.9''σ'' after foreground subtraction).<ref name="BICEP2_2014_1" /> However, on 19 June 2014, lowered confidence in confirming the [[cosmic inflation]] findings was reported;<ref name="NYT-20140619">
{{cite news
 |last=Overbye |first=D. |author-link=Dennis Overbye
 |date=19 June 2014
 |title=Astronomers Hedge on Big Bang Detection Claim
 |url=https://www.nytimes.com/2014/06/20/science/space/scientists-debate-gravity-wave-detection-claim.html
 |work=[[The New York Times]]
 |access-date=2014-06-20
}}</ref><ref name="BBC-20140619">
{{cite news
 |last=Amos |first=J.
 |date=19 June 2014
 |title=Cosmic inflation: Confidence lowered for Big Bang signal
 |url=https://www.bbc.com/news/science-environment-27935479
 |work=[[BBC News]]
 |access-date=2014-06-20
}}</ref> the accepted and reviewed version of the discovery paper contains an appendix discussing the possible production of the signal by [[cosmic dust]].<ref name="BICEP2_2014_1" /> In part because the large value of the tensor to scalar ratio, which contradicts limits from the [[Planck (spacecraft)|Planck]] data,<ref name="Planckcosmo">
{{cite journal
 |author=Planck Collaboration
 |date=2014
 |title=Planck 2013 results. XVI. Cosmological parameters
 |journal=[[Astronomy & Astrophysics]]
 |volume=571 |pages=16
 |arxiv=1303.5076
 |bibcode=2014A&A...571A..16P
 |doi=10.1051/0004-6361/201321591
|s2cid=118349591
 }}</ref> this is considered the most likely explanation for the detected signal by many scientists. For example, on June 5, 2014 at a conference of the [[American Astronomical Society]], astronomer [[David Spergel]] argued that the B-mode polarization detected by BICEP2 could instead be the result of light emitted from dust between the stars in our [[Milky Way]] galaxy.<ref>
{{cite web
 |last1=Urry |first1=M.
 |date=5 June 2014
 |title=What's behind the Big Bang controversy?
 |url=http://edition.cnn.com/2014/06/05/opinion/urry-big-bang/index.html
 |publisher=[[CNN]]
 |access-date=2014-06-06
}}</ref>

A [[preprint]] released by the [[Planck spacecraft|Planck]] team in September 2014, eventually accepted in 2016, provided the most accurate measurement yet of dust, concluding that the signal from dust is the same strength as that reported from BICEP2.<ref name="AXV-20140919">
{{cite journal
 |author=Planck Collaboration
 |year=2016
 |title=Planck intermediate results. XXX. The angular power spectrum of polarized dust emission at intermediate and high Galactic latitudes
 |journal=[[Astronomy & Astrophysics]]
 |volume=586 |issue=133
 |pages=A133
 |arxiv=1409.5738
 |bibcode= 2016A&A...586A.133P
 |doi=10.1051/0004-6361/201425034
|s2cid=9857299
 }}</ref><ref name="NYT-20140922">
{{cite news
 |last=Overbye |first=D. |author-link=Dennis Overbye
 |date=22 September 2014
 |title=Study Confirms Criticism of Big Bang Finding
 |url=https://www.nytimes.com/2014/09/23/science/space/study-confirms-criticism-of-big-bang-finding.html
 |work=The New York Times
 |access-date=2014-09-22
}}</ref> On January 30, 2015, a joint analysis of BICEP2 and [[Planck (spacecraft)|Planck]] data was published and the [[European Space Agency]] announced that the signal can be entirely attributed to [[Cosmic dust|dust]] in the Milky Way.<ref name="nature-20150130">
{{cite journal
 |last=Cowen |first=Ron
 |date=30 January 2015
 |title=Gravitational waves discovery now officially dead
 |journal=[[Nature (journal)|Nature]]
 |doi=10.1038/nature.2015.16830
|s2cid=124938210
 }}</ref>

BICEP2 has combined their data with the Keck Array and Planck in a joint analysis.<ref>
{{cite journal
 |author=BICEP2/Keck Array and Planck Collaborations
 |year=2015
 |title=Joint Analysis of BICEP2/Keck Array and Planck Data
 |journal=[[Physical Review Letters]]
 |volume=114 |issue=10 |pages=101301
 |arxiv=1502.00612
 |bibcode=2015PhRvL.114j1301B
 |doi=10.1103/PhysRevLett.114.101301
 |pmid=25815919
|s2cid=218078264
 }}</ref> A March 2015 publication in ''[[Physical Review Letters]]'' set a limit on the tensor-to-scalar ratio of {{nowrap|''r'' < 0.12}}.

The BICEP2 affair forms the subject of [[Brian_Keating#Losing_The_Nobel_Prize_(2018)|a book by Brian Keating]].

==Keck Array==
{| class="wikitable" style="float: right;"
|+ | The main properties of the BICEP instruments
|-
! Instrument !! Start !! End !! Frequency !! Resolution !! Sensors (pixels) !! Refs
|-
|rowspan=2| [[#BICEP1|BICEP]] || rowspan=2 | 2006 || rowspan=2 | 2008 || 100&nbsp;GHz || 0.93° || 50 (25) || <ref name="bicep_caltech" /><ref name="CaltechPressRelease" />
|-
| 150&nbsp;GHz || 0.60° || 48 (24) || <ref name="bicep_caltech" />
|-
| [[#BICEP2|BICEP2]] || 2010 || 2012 || 150&nbsp;GHz || 0.52° || 500 (250)<!--12 of 512 are dark--> || <ref name="BICEP2_2014_1" />
|-
|rowspan=4| [[#Keck Array|Keck Array]] || 2011 || 2011 ||rowspan=3| 150&nbsp;GHz ||rowspan=3| 0.52° || 1488 (744)<!--16 of 512 are dark--> ||rowspan=2| <ref name="keck_instrument" /><ref name="keck" />
|-
| 2012 || 2012 || 2480 (1240)<!--Expanded to 5 telescopes for 2012-->
|-
|rowspan=2| 2013 ||rowspan=2| 2018 || 1488 (744) ||rowspan=2| <ref name="keck" />
|-
| 95&nbsp;GHz || 0.7° || 992 (496)
|-
| [[#BICEP3|BICEP3]] || 2015 || — || 95&nbsp;GHz || 0.35°|| 2560 (1280) || <ref name="bicep3" />
|}
Immediately next to the BICEP telescope at the Martin A. Pomerantz Observatory building at the South Pole was an unused telescope mount previously occupied by the [[Degree Angular Scale Interferometer]].<ref name="kainanmaopho" /> The ''Keck Array'' was built to take advantage of this larger telescope mount. This project was funded by $2.3 million from [[W. M. Keck Foundation]], as well as funding from the [[National Science Foundation]], the [[Gordon and Betty Moore Foundation]], the James and Nelly Kilroy Foundation and the Barzan Foundation.<ref name="CaltechPressRelease" /> The Keck Array project was originally led by [[Andrew Lange]].<ref name="CaltechPressRelease" />

The Keck Array consists of five [[polarimeter]]s, each very similar to the BICEP2 design, but using a [[pulse tube refrigerator]] rather than a large liquid helium [[cryogenic storage dewar]].

The first three started observations in the [[austral summer]] of 2010–11; another two started observing in 2012. All of the receivers observed at 150&nbsp;GHz until 2013, when two of them were converted to observe at 100&nbsp;GHz.<ref name="keck" /> Each polarimeter consists of a [[refracting telescope]] (to minimise systematics) cooled by a [[pulse tube cryocooler|pulse tube cooler]] to 4 K, and a [[focal-plane array (radio astronomy)|focal-plane array]] of 512 [[transition edge sensor]]s cooled to 250 mK, giving a total of 2560 detectors, or 1280 dual-polarization pixels.<ref name="keck_instrument" />

In October 2018, the first results from the Keck Array (combined with BICEP2 data) were announced, using observations up to and including the 2015 season. These yielded an upper limit on cosmological B-modes of <math>r<0.07</math> (95% confidence level), which reduces to <math>r<0.06</math> in combination with [[Planck (satellite)|Planck]] data.<ref name="keck_x" />

In October 2021, new results were announced giving <math>r<0.036</math> (at 95% confidence level) based on BICEP/Keck 2018 observation season combined with Planck and [[Wilkinson Microwave Anisotropy Probe|WMAP]] data.<ref>{{Cite journal|last1=BICEP/Keck Collaboration|last2=Ade|first2=P. A. R.|last3=Ahmed|first3=Z.|last4=Amiri|first4=M.|last5=Barkats|first5=D.|last6=Thakur|first6=R. Basu|last7=Bischoff|first7=C. A.|last8=Beck|first8=D.|last9=Bock|first9=J. J.|last10=Boenish|first10=H.|last11=Bullock|first11=E.|date=2021-10-04|title=Improved Constraints on Primordial Gravitational Waves using Planck, WMAP, and BICEP/Keck Observations through the 2018 Observing Season|url=https://link.aps.org/doi/10.1103/PhysRevLett.127.151301|journal=Physical Review Letters|volume=127|issue=15|pages=151301|arxiv=2110.00483|doi=10.1103/PhysRevLett.127.151301|pmid=34678017 |bibcode=2021PhRvL.127o1301A |s2cid=238253204 }}</ref><ref>{{Cite journal|last=Meerburg|first=Daniel|date=2021-10-04|title=Squeezing down the Theory Space for Cosmic Inflation|url=https://physics.aps.org/articles/v14/135|journal=Physics|language=en|volume=14|page=135 |doi=10.1103/Physics.14.135 |bibcode=2021PhyOJ..14..135M |s2cid=239251554 |doi-access=free}}</ref>

==BICEP3==
Once the Keck array was completed in 2012, it was no longer cost-effective to continue to operate BICEP2. However, using the same technique as the Keck array to eliminate the large liquid helium [[Cryogenic storage dewar|dewar]], a much larger telescope has been installed on the original BICEP telescope mount.

BICEP3 consists of a single telescope with the same 2560 detectors (observing at 95&nbsp;GHz) as the five-telescope Keck array, but a 68&nbsp;cm aperture,<ref>[http://workshops.ift.uam-csic.es/files/177/Ahmed.pdf Updates from the BICEP/Keck Array Collaboration] Zeeshan Ahmed KIPAC, Stanford University 08 June 2015</ref> providing roughly twice the optical throughput of the entire Keck array. One consequence of the large focal plane is a larger 28° field of view,<ref name="arxiv_14075928">{{cite book
 |last1=Ahmed |first1=Z.
 |last2=Amiri |first2=M.
 |last3=Benton |first3=S.J.
 |last4=Bock |first4=J.J.
 |last5=Bowens-Rubin |first5=R.
 |last6=Buder |first6=I.
 |last7=Bullock |first7=E.
 |last8=Connors |first8=J.
 |last9=Filippini |first9=J.P.
 |last10=Grayson |first10=J.A.
 |last11=Halpern |first11=M.
 |display-authors=etal
 |date=2014
 |chapter=BICEP3: A 95GHz refracting telescope for degree-scale CMB polarization
 |editor1-last=Holland |editor1-first=Wayne S.
 |editor2-last=Zmuidzinas |editor2-first=Jonas
 |title=Millimeter, Submillimeter, and Far-Infrared Detectors and Instrumentation for Astronomy VII
 |series=[[Proceedings of SPIE]]
 |volume=9153 |pages=91531N
 |arxiv=1407.5928
 |bibcode=2014SPIE.9153E..1NA
 |doi=10.1117/12.2057224
 |s2cid=7249387
}}</ref> which will necessarily mean scanning some foreground-contaminated portions of the sky. It was installed (with initial configuration) at the pole in January 2015.<ref name="bicep3" /><ref>
{{Cite news
 |last=Briggs |first=D.
 |date=10 March 2015
 |title=BICEP: From the South Pole to the beginning of time
 |url=https://www.bbc.co.uk/news/science-environment-31798012
 |work=[[BBC News]]
}}</ref> It was upgraded for the 2015-2016 Austral summer season to a full 2560 detector configuration. BICEP3 is also a prototype for the BICEP Array.<ref>{{Cite web | url=http://cosmology.caltech.edu/projects/BICEP3 |title = BICEP3 - Caltech Observational Cosmology}}</ref>

==BICEP Array==
{{Update|section|date=January 2022}}
The Keck array is being succeeded by the BICEP array, which consists of four BICEP3-like telescopes on a common mount, operating at 30/40, 95, 150 and 220/270 GHz.<ref>{{cite journal
 |title=Design and Performance of the First BICEP Array Receiver
 |first1=Alessandro |last1=Schillaci |display-authors=etal
 |journal=Journal of Low Temperature Physics
 |volume=199 |issue=3–4 |pages=976–984 |date=17 February 2020
 |doi=10.1007/s10909-020-02394-6 |bibcode=2020JLTP..199..976S |arxiv=2002.05228
 |s2cid=204954127 |url=http://orca.cf.ac.uk/130169/1/2002.05228.pdf
}}</ref>  Installation began between the 2017 and 2018 observing seasons. It is scheduled to be fully installed by the 2020 observing season.<ref name=BICEPArray>{{cite web |title=BICEP Array - Caltech Observational Cosmology |url=http://cosmology.caltech.edu/projects/BICEP_Array |website=cosmology.caltech.edu |language=en}}</ref><ref name="aps_physics_20201030">{{cite journal |last1=Rini |first1=Mateo |title=Hunting Season for Primordial Gravitational Waves |journal=Physics |date=October 30, 2020 |volume=13 |page=164 |doi=10.1103/Physics.13.164 |url=https://physics.aps.org/articles/v13/164 |access-date=10 November 2020|doi-access=free |bibcode=2020PhyOJ..13..164R }}</ref>

According to the project website: "BICEP Array will measure the polarized sky in five frequency bands to reach an ultimate sensitivity to the amplitude of IGW [inflationary gravitational waves] of σ(r) < 0.005" and "This measurement will be a definitive test of slow-roll models of inflation, which generally predict a gravitational-wave signal above approximately 0.01."{{r|BICEPArray}}

==See also==
{{div col|colwidth=20em}}
*[[Cosmology]]
*[[Inflation (cosmology)]]
*[[Atacama Cosmology Telescope]]
*[[South Pole Telescope]]
*[[Cosmology Large Angular Scale Surveyor]]
*[[POLARBEAR]]
*[[LiteBIRD]], space-based CMB B-mode polarization search project
*[[Spider (polarimeter)|Spider]], balloon-based CMB B-mode polarization project
{{div col end}}

==References==
{{Reflist|2|refs=
<!--- BICEP --->
<ref name="bicep_caltech">{{cite web
 |title=BICEP: Robinson Gravitational Wave Background Telescope
 |url=https://cosmology.caltech.edu/projects/BICEP
 |publisher=[[Caltech]]
 |access-date=2022-10-07
 }}</ref>
<ref name="bicep1_collaboration">
{{cite web
 |title=BICEP1 Collaboration
 |url=http://www.cfa.harvard.edu/CMB/bicep1/collaboration.html
 |publisher=[[Harvard–Smithsonian Center for Astrophysics]]
 |access-date=2014-03-14
}}</ref>
<!--- BICEP2 --->
<ref name="bicep2">
{{cite book
 |last=Ogburn |first=R. W.
 |display-authors=etal
 |year=2010
 |chapter=The BICEP2 CMB polarization experiment
 |chapter-url=https://authors.library.caltech.edu/71600/
 |editor1-last=Holland |editor1-first=Wayne S.
 |editor2-last=Zmuidzinas |editor2-first=Jonas
 |title=Millimeter, Submillimeter, and Far-Infrared Detectors and Instrumentation for Astronomy V
 |series=[[Proceedings of SPIE]]
 |volume=7741 |page=77411G
 |bibcode=2010SPIE.7741E..1GO
 |doi=10.1117/12.857864
 |s2cid=29118984
 |url=<!-- -->
 }}</ref>
<ref name="bicep2_collaboration">
{{cite web
 |title=Collaboration – BICEP2 South Pole
 |url=http://www.cfa.harvard.edu/CMB/bicep2/collaboration.html
 |publisher=[[Harvard–Smithsonian Center for Astrophysics]]
 |access-date=2014-03-14
}}</ref>
<ref name="bmodes">
{{cite news
 |url=https://www.theguardian.com/science/2014/mar/14/gravitational-waves-big-bang-universe-bicep
 |title=Gravitational waves: Have US scientists heard echoes of the big bang?
 |newspaper=[[The Guardian]]
 |date=2014-03-14
 |access-date=2014-03-14
}}</ref>
<ref name="BICEP2_2014_1">{{Cite Q|Q27012172}}</ref>
<ref name="BICEP2_2014_2">
{{cite journal
 |last1=Ade |first1=P. A. R.
 |display-authors=etal.
 |year=2014
 |title=BICEP2. II. Experiment and Three-year Data Set
 |journal=The Astrophysical Journal
 |volume=792 |issue=1 |pages=62
 |arxiv=1403.4302
 |bibcode=2014ApJ...792...62B
 |doi=10.1088/0004-637X/792/1/62
|s2cid=18486247
 }}</ref>
<ref name="BICEP2-2014">
{{cite web
 |author=Staff
 |date=17 March 2014
 |title=BICEP2 2014 Results Release
 |url=http://bicepkeck.org
 |publisher=[[National Science Foundation]]
 |access-date=18 March 2014
}}</ref>
<ref name="NASA-20140317">
{{cite web
 |last=Clavin |first=W.
 |date=17 March 2014
 |title=NASA Technology Views Birth of the Universe
 |url=http://www.jpl.nasa.gov/news/news.php?release=2014-082
 |publisher=[[NASA]]
 |access-date=17 March 2014
}}</ref>
<ref name="NYT-20140317">
{{cite news
 |last=Overbye |first=D. |author-link=Dennis Overbye
 |date=17 March 2014
 |title=Detection of Waves in Space Buttresses Landmark Theory of Big Bang
 |url=https://www.nytimes.com/2014/03/18/science/space/detection-of-waves-in-space-buttresses-landmark-theory-of-big-bang.html
 |work=The New York Times
 |access-date=17 March 2014
}}</ref>
<ref name="NYT-20140324">
{{cite news
 |last=Overbye |first=D. |author-link=Dennis Overbye
 |date=24 March 2014
 |title=Ripples From the Big Bang
 |url=https://www.nytimes.com/2014/03/25/science/space/ripples-from-the-big-bang.html
 |work=The New York Times
 |access-date=24 March 2014
}}</ref>
<!--- Keck --->
<ref name="CaltechPressRelease">
{{cite web
 |title=W.M. Keck Foundation Gift to Enable Caltech and JPL Scientists to Research the Universe's Violent Origin 
 |url=http://media.caltech.edu/press_releases/13201 
 |publisher=[[Caltech]] 
 |url-status=dead 
 |archive-url=https://web.archive.org/web/20120302003022/http://media.caltech.edu/press_releases/13201 
 |archive-date=2012-03-02 
}}</ref>
<ref name="keck">
{{cite web
 |title=Keck Array South Pole
 |url=http://www.cfa.harvard.edu/CMB/keckarray/
 |publisher=[[Harvard–Smithsonian Center for Astrophysics]]
 |access-date=2014-03-14
}}</ref>
<ref name="keck_instrument">
{{cite web
 |title=Instrument – Keck Array South Pole
 |url=http://www.cfa.harvard.edu/CMB/keckarray/instrument.html/
 |publisher=[[Harvard–Smithsonian Center for Astrophysics]]
 |access-date=2014-03-14
}}</ref>
<ref name="keck_collaboration">
{{cite web
 |title=Collaboration – Keck Array South Pole
 |url=http://www.cfa.harvard.edu/CMB/keckarray/collaboration.html
 |publisher=[[Harvard–Smithsonian Center for Astrophysics]]
 |access-date=2014-03-14
}}</ref>
<ref name="2002NSFgrant">
{{cite web
 |title=NSF Award Abstract #0230438
 |url=https://www.nsf.gov/awardsearch/showAward?AWD_ID=0230438&HistoricalAwards=false
 |publisher=[[National Science Foundation]]
 |access-date=2014-03-26
}}</ref>
<ref name="keck_x">{{cite journal |author=Keck Array, BICEP2 Collaborations |title=BICEP2 / Keck Array x: Constraints on Primordial Gravitational Waves using Planck, WMAP, and New BICEP2/Keck Observations through the 2015 Season |journal=Phys. Rev. Lett. |volume=121 |issue=22 |pages=221301 |date=11 October 2018 |arxiv=1810.05216|doi=10.1103/PhysRevLett.121.221301 |pmid=30547645 |s2cid=56174788 }}</ref>
<!--- BICEP3 --->
<ref name="bicep3">
{{cite web
 |title=BICEP3
 |url=http://www.cfa.harvard.edu/CMB/bicep3/
 |publisher=[[Harvard–Smithsonian Center for Astrophysics]]
 |access-date=2014-03-14
}}</ref>
<ref name="bicep3_collaboration">
{{cite web
 |title=BICEP3 Collaboration
 |url=http://www.cfa.harvard.edu/CMB/bicep3/collaboration.html
 |publisher=[[Harvard–Smithsonian Center for Astrophysics]]
 |access-date=2014-03-14
}}</ref>
<ref name="kainanmaopho">
{{cite web
 |title=MAPO Open House
 |url=https://kateinantarctica.wordpress.com/2015/05/07/mapo-open-house/
 |publisher=kateinantarctica.wordpress.com
 |date=2014-12-14
 |access-date=2018-03-22
}}</ref>
}}

==External links==
{{Commons category|BICEP}}
*[https://web.archive.org/web/20151203234039/http://www.adventure-antarctica.de/ BICEP2 winter-over (2009–2012) Steffen Richter (9 winters at the South Pole).]
*[http://www.antarctic-adventures.de/ Keck winter-over (2010-current) Robert Schwarz (12 winters at the South Pole).]
{{CMB experiments}}

{{DEFAULTSORT:Bicep}}
[[Category:Radio telescopes]]
[[Category:Physics experiments]]
[[Category:Cosmic microwave background experiments]]
[[Category: Astronomical experiments in the Antarctic]]
[[Category:Inflation (cosmology)]]