Speaker
Description
The Simons Observatory (SO) consists of one large aperture and three small aperture telescopes currently operating in four frequency bands between 90-280 GHz, located at ∼5,200m altitude in the Atacama Desert of Chile. SO is dedicated to observing the polarized cosmic microwave background (CMB), among other science goals, with the primary focus of the small aperture telescopes (SATs) being to constrain the primordial B-mode polarization signal. The SATs, each containing ~10,000 detectors, utilize a cryogenic continuously rotating half-wave plate (CHWP) consisting of a sapphire stack and superconducting magnetic bearing. The CHWP spins at frequency 𝑓~2Hz and aims to mitigate the atmospheric noise and systematic uncertainties to recover the large-scale CMB polarization signal. The second harmonic of the HWP rotation frequency (2𝑓 at 4 Hz) has a contribution from differential transmission that is linearly correlated with atmospheric temperature. Therefore, we can fit the 2𝑓 signal with measured precipitable water vapor (PWV) for values below 3mm. Since the 2𝑓 signal is independent of the polarization modulation, which occurs at 4𝑓, the 2𝑓 signal may be a useful calibration method. We explore this method as a possible relative calibration between detector responsivities, as well as overall detector responsivity over different seasons of observations.
| Would you be interested in presenting a poster if the conference is oversubcribed? | Yes |
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