MAXIPOL Scan Strategy

The small size of the expected CMB polarization anisotropy signal demands a scan strategy with strong measurement and rejection of systematic effects. Our scan strategy builds on the those of the successful MAX and MAXIMA experiments. To control systematic effects on any single time scale, we will scan the sky using three temporal modulations: the primary mirror is scanned with a period of 0.5 s, the gondola is scanned in azimuth with a period of 1 minute, and pixels are measured by different elements in the array on time scales of minutes up to several hours.

The scan strategy is illustrated above. All modulations of the beams on the sky are done in constant elevation and are centered on a reference star. The primary mirror modulates 0.8 degrees p-p at 2 Hz while simultaneously the gondola is also scanned 0.8 degrees p-p with the scan centered on a reference star. As the sky rotates a ``bow-tie'' shaped region of the sky is swept out. This strategy produces highly cross-linked scans, thus greatly reducing striping due to long term noise drifts.