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, the BICEP/Keck program observe the polarization of the Cosmic Microwave Background from 95GHz to 270GHz.
BICEP3 is a wide-field cryogenic refractor, with a 55cm aperture and fast optics it achieves an order of magnitude increase in throughput compare to previous telescopes in the BICEP series. It is also prototype for the four BICEP3-sized receivers of the BICEP Array, which will replace Keck Array over the next several years and will include a total of over 30,000 detectors in five frequency bands.
BICEP3 is a 520mm aperture, compact two-lens refractor designed to observe the polarization of the cosmic microwave background (CMB) at 95 GHz. Its focal plane consists of modularized tiles of antenna-coupled transition edge sensors (TESs), similar to those used in Bicep 2 and the Keck Array. The increased per-receiver optical throughput compared to Bicep 2/Keck Array, due to both its faster f/1.7 optics and the larger aperture, will more than double the combined mapping speed of the Bicep /Keck program.
Details of the instrument design and performances can be found in Bicep /Keck Collaboration et al. (2022), and the science result using data from 2016-2018 can be found in BICEP/Keck Collaboration et al. (2022).