A CMBPOL mission concept: feed farm on a simple spinner

We present a concept for a medium scale satellite mission to measurement the Bmode polarization in the CMB at large angular scales. The idea is to close pack a multifrequency array of ∼1500 corrugated feeds to make a “feed farm”. The majority point along the spin axis of the satellite. The primary modulation is obtained by spinning the satellite. Thus, in any instant the polarization in one direction is measured very well. The spin axis is then smoothly precessed over the celestial sphere. An angular resolution of better than 2.5◦ is possible at 150 GHz. Little detector development is needed; indeed the requisite sensitivity has nearly been achieved. The technical challenges are in the cryogenics and in the manufacture of corrugated feeds above 200 GHz. The astrophysical challenge is in the foreground emission. In the absence of foreground emission the raw sensitivity of a simple feed farm observing for one year corresponds to r < 0.005