Browsing by Author "Eimer, Joseph"

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    Cosmology Large Angular Scale Surveyor (CLASS): 90 GHz Telescope Pointing, Beam Profile, Window Function, and Polarization Performance
    (2024) Datta, Rahul; Brewer, Michael K.; Couto, Jullianna Denes; Eimer, Joseph; Li, Yunyang; Xu, Zhilei; Ali, Aamir; Appel, John W.; Bennett, Charles L.; Bustos, Ricardo; Chuss, David T.; Cleary, Joseph; Dahal, Sumit; Inostroza, Francisco Raul Javier Espinoza; Essinger-Hileman, Thomas; Fluxa, Pedro; Harrington, Kathleen; Helson, Kyle; Iuliano, Jeffrey; Karakla, John; Marriage, Tobias A.; Novack, Sasha; Nunez, Carolina; Padilla, Ivan L.; Parker, Lucas; Petroff, Matthew A.; Reeves, Rodrigo; Rostem, Karwan; Shi, Rui; Valle, Deniz A. N.; Watts, Duncan J.; Weiland, Janet L.; Wollack, Edward J.; Zeng, Lingzhen
    The Cosmology Large Angular Scale Surveyor (CLASS) is a telescope array that observes the cosmic microwave background (CMB) over similar to 75% of the sky from the Atacama Desert, Chile, at frequency bands centered near 40, 90, 150, and 220 GHz. CLASS measures the large angular scale CMB polarization to constrain the tensor-to-scalar ratio and the optical depth to last scattering. This paper presents the optical characterization of the 90 GHz telescope. Observations of the Moon establish the pointing while dedicated observations of Jupiter are used for beam calibration. The standard deviations of the pointing error in azimuth, elevation, and boresight angle are 1.' 3, 2.' 1, and 2.' 0, respectively, over the first 3 yr of observations. This corresponds to a pointing uncertainty similar to 7% of the beam's full width at half-maximum (FWHM). The effective azimuthally symmetrized instrument 1D beam estimated at 90 GHz has an FWHM of 0.degrees 620 +/- 0.degrees 003 and a solid angle of 138.7 +/- 0.6(stats.) +/- 1.1(sys.) mu sr integrated to a radius of 4 degrees. The corresponding beam window function drops to b & ell;2=0.93,0.71,0.14 at & ell; = 30, 100, 300, respectively. Far-sidelobes are studied using detector-centered intensity maps of the Moon and measured to be at a level of 10-3 or below relative to the peak. The polarization angle of Tau A estimated from preliminary survey maps is 149 degrees.6 +/- 0 degrees.2(stats.) in equatorial coordinates. The instrumental temperature-to-polarization (T -> P) leakage fraction, inferred from per-detector demodulated Jupiter scan data, has a monopole component at the level of 1.7 x 10-3, a dipole component with an amplitude of 4.3 x 10-3, with no evidence of quadrupolar leakage.
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    Four-year Cosmology Large Angular Scale Surveyor (CLASS) Observations: On-sky Receiver Performance at 40, 90, 150, and 220 GHz Frequency Bands
    (2022) Dahal, Sumit; Appel, John W.; Datta, Rahul; Brewer, Michael K.; Ali, Aamir; Bennett, Charles L.; Bustos, Ricardo; Chan, Manwei; Chuss, David T.; Cleary, Joseph; Couto, Jullianna D.; Denis, Kevin L.; Dunner, Rolando; Eimer, Joseph; Espinoza, Francisco; Essinger-Hileman, Thomas; Golec, Joseph E.; Harrington, Kathleen; Helson, Kyle; Iuliano, Jeffrey; Karakla, John; Li, Yunyang; Marriage, Tobias A.; McMahon, Jeffrey J.; Miller, Nathan J.; Novack, Sasha; Nunez, Carolina; Osumi, Keisuke; Padilla, Ivan L.; Palma, Gonzalo A.; Parker, Lucas; Petroff, Matthew A.; Reeves, Rodrigo; Rhoades, Gary; Rostem, Karwan; Valle, Deniz A. N.; Watts, Duncan J.; Weiland, Janet L.; Wollack, Edward J.; Xu, Zhilei
    The Cosmology Large Angular Scale Surveyor (CLASS) observes the polarized cosmic microwave background (CMB) over the angular scales of 1 degrees less than or similar to theta <= 90 degrees with the aim of characterizing primordial gravitational waves and cosmic reionization. We report on the on-sky performance of the CLASS Q-band (40 GHz), W-band (90 GHz), and dichroic G-band (150/220 GHz) receivers that have been operational at the CLASS site in the Atacama desert since 2016 June, 2018 May, and 2019 September, respectively. We show that the noise-equivalent power measured by the detectors matches the expected noise model based on on-sky optical loading and lab-measured detector parameters. Using Moon, Venus, and Jupiter observations, we obtain power to antenna temperature calibrations and optical efficiencies for the telescopes. From the CMB survey data, we compute instantaneous array noise-equivalent-temperature sensitivities of 22, 19, 23, and 71 mu K-cmp root s for the 40, 90, 150, and 220 GHz frequency bands, respectively. These noise temperatures refer to white noise amplitudes, which contribute to sky maps at all angular scales. Future papers will assess additional noise sources impacting larger angular scales.