The Keck Array CMB polarimeter overview and status

The Keck Array is a CMB polarimeter observing at the geographic South Pole for its third season. The instrument is optimized to measure the inflationary polarization signal in the cosmic microwave background. We use the minimum necessary aperture to resolve degree-scale polarization features. This allows us to simultaneously deploy five compact receivers to maximize the number of detectors and sensitivity. We have upgraded the instrument with new detector arrays for improved instrumental sensitivity for our third year of observation. I will discuss recent upgrades and instrument characterization, and show progress toward new cosmological constraints.