How QUaD (and BICEP) Work



Bolometer temperature coupled to temperature of incoming radiation from small "spots" on the sky
Two orthogonal absorber grids read out independently
Sum measures total intensity
Difference measures polarization
Whole telescope moves (scans), sweeping the set of pencil beams around on the sky
We read out the *changing* bolometer temperature as a function of pointing position - called timestream data...