From left to right: the BICEP1, BICEP2 and Keck Array, situated at the South Pole. Photo credit: Steffen Richter (BICEP1 and BICEP2), Robert Schwartz (Keck Array).


Background Imaging of Cosmic Extragalactic Polarization (BICEP1) was a bolometric polarimeter designed to measure the inflationary B-mode polarization of the cosmic microwave background at degree angular scales. The instrument comprised a two-lens refracting telescope coupled to a focal plane of 49 orthogonal pairs of horn-coupled polarization-sensitive bolometers operating at 100 and 150 GHz. BICEP1 observed from the Amundsen-Scott South Pole Station between 2006 and 2008, mapping about 2% of the sky chosen to be uniquely clean of polarized foreground emission.


The BICEP/Keck project includes a multi-generational series of CMB polarization experiments. Experiments in the series are listed below.:


BICEP2 was a 26-cm refracting telescope that observed the cosmic microwave background (CMB) from the National Science Foundation's Amundsen-Scott South Pole Station from 2010-2012. It was designed to observe the polarization of the CMB on angular scales around one degree, near the expected peak of the B-mode polarization signal produced by inflationary gravitational waves. BICEP2 observed a patch of 400 square degrees in a single frequency band at 150 GHz.

Keck Array

The Keck Array consists of five BICEP2-style receivers in a single telescope mount at the South Pole. The Keck Array observes the same field as BICEP2, with five receivers beginning in 2012. These were initially all at 150 GHz; in the 2014 season two were replaced with receivers at 95 GHz; and in the 2015 season an additional two have been replaced with receivers at 220 GHz.


BICEP3, the successor to BICEP2, was deployed to the Dark Sector Laboratory at Amundsen-Scott South Pole Station in the 2014-2015 Austral summer season. It was upgraded in 2015-2016 to a full 2560 detectors operating at 95 GHz, together with Keck Array. It is also the prototype for the four BICEP3-sized receivers of the BICEP Array, which will replace Keck Array over the next several years.


The BICEP Array telescope is a set of multi-frequency cameras designed to constrain the energy scale of inflation through CMB B-mode searches while also controlling the polarized galactic foregrounds. The lowest frequency BICEP Array receiver (BA1) has been observing from the South Pole since 2020 and provides 30 GHz and 40 GHz data to characterize the Galactic synchrotron in the BICEP/Keck CMB maps. Deployment of the 150 GHz BICEP Array receiver (BA2) is planned for 2023. Deployment of the 270 GHz BICEP Array receiver as well as the TKIDs demo camera is planned for the following year.

The official website for results from these experiments may be found at can be found at; data hosted on LAMBDA originate from this site. The BICEP/Keck Project has made the most sensitive measurements to date of the polarization of the CMB.

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