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MSAM1-94: repeated measurement of medium-scale anisotropy in the cosmic microwave background radiation

Abstract

The second flight of the Medium Scale Anisotropy Measurement (MSAM1-94) observed the same field as the first flight (MSAM1-92) to confirm our earlier measurement of cosmic microwave background radiation (CMBR) anisotropy. This instrument chops a 30\arcmin\ beam in a 3 position pattern with a throw of \pm40\arcmin, and simultaneously measures single and double differenced sky signals. We observe in four spectral channels centered at 5.6, 9.0, 16.5, and 22.5~\icm, providing sensitivity to the peak of the CMBR and to thermal emission from interstellar dust. The dust component correlates well with the \IRAS\ 100~\micron\ map. The CMBR observations in our double difference channel correlate well with the earlier observations, but the single difference channel shows some discrepancies. We obtain a detection of fluctuations in the MSAM1-94 dataset that match CMBR in our spectral bands of \Delta T/T = 1.9^{+1.3}_{-0.7}\times 10^{-5} (90\% confidence interval, including calibration uncertainty) for total rms Gaussian fluctuations with correlation angle 0\fdg3, using the double difference demodulation

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