We present the first sky maps from the BEAST (Background Emission Anisotropy Scanning Telescope) experiment. BEAST consists of a 2.2 m off-axis Gregorian telescope fed by a cryogenic millimeter wavelength focal plane currently consisting of six Q band (40 GHz) and two Ka band (30 GHz) scalar feed horns feeding cryogenic HEMT amplifiers. Data were collected from two balloon-borne flights in 2000, followed by a lengthy ground observing campaign from the 3.8 km altitude University of California White Mountain Research Station. This paper reports the initial results from the ground-based observations. The instrument produced an annular map covering the sky over 33 degrees < delta < 42 degrees. The maps cover an area of 2470 deg(2) with an effective resolution of 23' FWHM at 40 GHz and 30' at 30 GHz. The map rms (smoothed to 300 and excluding Galactic foregrounds) is 57 +/- 5 mu K (Rayleigh-Jeans) at 40 GHz. Comparison with the instrument noise and correcting for 5% atmospheric attenuation gives a cosmic signal rms contribution of 29 +/- 3 mu K (R-J) or 30 +/- 3 mu K relative to a Planck blackbody of 2.7 K. An estimate of the actual cosmic microwave background (CMB) sky signal requires taking into account the l space filter function of our experiment and analysis techniques, carried out in a companion paper. In addition to the robust detection of CMB anisotropies, we find a strong correlation between small portions of our maps and features in recent H alpha maps. In this work we describe the data set and analysis techniques leading to the maps, including data selection, filtering, pointing reconstruction, mapmaking algorithms, and systematic effects

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The Background Emission Anisotropy Scanning Telescope ( BEAST) is a 2.2 m off-axis telescope with an eightelement mixed Q-band (38-45 GHz) and focal plane, designed for balloon-borne and ground-based studies of the cosmic microwave background (CMB). Here we present the CMB angular power spectrum calculated from 682 hr of data observed with the BEAST instrument. We use a binned pseudo-C l estimator (the MASTER method). We find results that are consistent with other determinations of the CMB anisotropy for angular wavenumbers l between 100 and 600. We also perform cosmological parameter estimation. The BEAST data alone produce a good constraint on k 1 À tot ¼ À0:074 AE 0:070, consistent with a flat universe. A joint parameter estimation analysis with a number of previous CMB experiments produces results consistent with previous determinations. Subject heading gs: cosmic microwave background -cosmology: observations -large-scale structure of universe Online material: color figure

We present the angular power spectrum of the cosmic microwave background (CMB) component extracted with fastica from the Background Emission Anisotropy Scanning Telescope (BEAST) data. BEAST is a 2.2‐m off‐axis telescope with a focal plane comprising eight elements at Q (38–45 GHz) and Ka (26–36 GHz) bands. It operates from the UC (University of California) White Mountain Research Station at an altitude of 3800 m. The BEAST CMB angular power spectrum has already been calculated by O'Dwyer et al. using only the Q‐band data. With two input channels, fastica returns two possible independent components. We found that one of these two has an unphysical spectral behaviour, while the other is a reasonable CMB component. After a detailed calibration procedure based on Monte Carlo (MC) simulations, we extracted the angular power spectrum for the identified CMB component and found a very good agreement with the already published BEAST CMB angular power spectrum and with the Wilkinson Microwave Anisotropy Probe (WMAP) data.

The Background Emission Anisotropy Scanning Telescope (BEAST) is a millimeter wavelength experiment designed to generate maps of fluctuations in the cosmic microwave background (CMB). The telescope is composed of an off-axis Gregorian optical system with a 2.2 m primary that focuses the collected microwave radiation onto an array of cryogenically cooled high electron mobility transistor (HEMT) receivers. This array is composed of six corrugated scalar feed horns in the Q band (38 to 45 GHz) and two more in the Ka band (26 to 36 GHz) with one of the six Q-band horns connected to an ortho-mode transducer for extraction of both polarizations incident on the single feed. The system has a minimum beam size of 200 with an average sensitivity of 900 mu K root s per receiver. This paper describes the design and performance of the BEAST instrument and provides the details of subsystems developed and used toward the goal of generating a map of CMB fluctuations on 200 scales with sensitivity in l space between l similar to 100 and l similar to 500. A map of the CMB centered on the north celestial pole has been generated from the BEAST telescope in a 9 degrees wide annulus at declination 37 degrees with a typical pixel error of 57 +/- 5 mu K when smoothed to 300 resolution. A brief summary of the map and results generated by an observing campaign at the University of California White Mountain Research Station are also included