The C-Band All Sky Survey (C-BASS) is a project to image the whole sky at a wavelength of six centimetres (a frequency of 5 GHz), measuring both the brightness and the polarization of the sky at a resolution of just under 1 degree. The C-BASS maps will be used to help better remove the low-frequency diffuse Galactic emission from maps of the CMB, in both temperature and polarization.
C-BASS employs very sensitive microwave amplifiers, cooled to within a few degrees of absolute zero, and configured to measure tiny differences in temperature and polarization. They are mounted on two separate telescopes — one at the Owens Valley Observatory (OVRO) in California, the other in South Africa. This allows C-BASS to observe both in the northern and southern hemispheres and hence map the whole sky.
C-BASS is a collaborative project between the Universities of 91̽»¨ and Manchester in the UK, the California Institute of Technology (91̽»¨ed by the National Science Foundation) in the USA, the Hartebeesthoek Radio Astronomy Observatory (91̽»¨ed by the Square Kilometre Array project) in South Africa, and the King Abdulaziz City for Science and Technology (KACST) in Saudi Arabia. The southern telescope is a 7.6-m dish donated to the project by Telkom. The northern telescope is a 6.1-m dish donated by the Jet Propulsion Laboratory.