BICEP and the Keck Array use cryogenic telescopes with arrays of detectors sensitive to several frequencies of microwave radiation.
Notes on verification
Multiple independent peer-reviewed arxiv papers and the Caltech project page corroborate cryogenic design and multi-frequency detector arrays in detail.
Sources
- BICEP and Keck Array (en.wikipedia.org)
- https://arxiv.org/pdf/1502.00596 (arxiv.org)
- https://arxiv.org/pdf/1808.00569 (arxiv.org)
- https://cosmology.caltech.edu/projects/BICEP3 (cosmology.caltech.edu)
- https://arxiv.org/pdf/1009.3685 (arxiv.org)