New Cosmic Microwave Background Power Spectrum Constraints from MSAM1

We present new cosmic microwave background (CMB) anisotropy results from the combined analysis of the three ights of the rst Medium Scale Anisotropy Measurement (MSAM1). This balloon-borne bolometric instrument measured about 10 deg2 of sky at half-degree resolution in four frequency bands from 5.2 to 20 cm~1 with a high signal-to-noise ratio. Here we present an overview of our analysis methods, compare the results from the three ights, derive new constraints on the CMB power spectrum from the combined data, and reduce the data to total power Wiener-ltered maps of the CMB. A key feature of this new analysis is a determination of the amplitude of CMB uctuations at l D 400. The analysis technique is described in a companion paper (L. Knox).