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تسجيل مستخدم جديدOn-sky performance of the CLASS Q-band telescope
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The Cosmology Large Angular Scale Surveyor (CLASS) is mapping the polarization of the Cosmic Microwave Background (CMB) at large angular scales ($2<elllesssim200$) in search of a primordial gravitational wave B-mode signal down to a tensor-to-scalar ratio of $r approx 0.01$. The same data set will provide a near sample-variance-limited measurement of the optical depth to reionization. Between June 2016 and March 2018, CLASS completed the largest ground-based Q-band CMB survey to date, covering over 31 000~square-degrees (75% of the sky), with an instantaneous array noise-equivalent temperature (NET) sensitivity of $32~mu mbox{K}_{cmb}sqrt{mbox{s}}$. We demonstrate that the detector optical loading ($1.6~mbox{pW}$) and noise-equivalent power ($19~mbox{aW}sqrt{mbox{s}}$) match the expected noise model dominated by photon bunching noise. We derive a $13.1pm0.3~mbox{K/pW}$ calibration to antenna temperature based on Moon observations, which translates to an optical efficiency of $0.48pm0.04$ and a $27~mbox{K}$ system noise temperature. Finally, we report a Tau A flux density of $308pm11~mbox{Jy}$ at $38.4pm0.2~mbox{GHz}$, consistent with the WMAP Tau A time-dependent spectral flux density model.
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