  We present Cosmic Microwave Background (CMB) maps from the Santa Barbara
HACME balloon experiment (Staren etal 2000), covering about 1150 square degrees
split between two regions in the northern sky, near the stars gamma Ursae
Minoris and alpha Leonis, respectively. The FWHM of the beam is about 0.77
degrees in three frequency bands centered on 39, 41 and 43 GHz. The results
demonstrate that the thoroughly interconnected scan strategy employed allows
efficient removal of 1/f-noise and slightly variable scan-synchronous offsets.
The maps display no striping, and the noise correlations are found to be
virtually isotropic, decaying on an angular scale around one degree. The noise
performance of the experiment resulted in an upper limit on CMB anisotropy.
However, our results demonstrate that atmospheric contamination and other
systematics resulting from the circular scanning strategy can be accurately
controlled, and bodes well for the planned follow-up experiments BEAST and ACE,
since they show that even with the overly cautious assumption that 1/f-noise
and offsets will be as dominant as for HACME, the problems they pose can be
readily overcome with the mapmaking algorithm discussed. Our prewhitened
notch-filter algorithm for destriping and offset removal should be useful also
for other balloon- and ground-based experiments whose scan strategies involve
substantial interleaving.

Astrophysics