Abstract
The Simons Observatory (SO) is an upcoming cosmic microwave background (CMB) experiment located on Cerro Toco, Chile, that will map the microwave sky in temperature and polarization in six frequency bands spanning 27 to 285 GHz. SO will consist of one 6-m large aperture telescope fielding \(\sim\) 30,000 detectors and an array of three 0.42-m small aperture telescopes (SATs) fielding an additional 30,000 detectors. This synergy will allow for the extremely sensitive characterization of the CMB over angular scales ranging from an arcmin to tens of degrees, enabling a wide range of scientific output. Here we focus on the SATs targeting degree angular scales with successive dichroic instruments observing at mid-frequency (MF: 93/145 GHz), ultra-high-frequency (UHF: 225/285 GHz), and low-frequency (LF: 27/39 GHz). The three SATs will be able to map \(\sim\) 10% of the sky to a noise level of \(\sim\)\(2\,\upmu {\hbox {K}}\)-arcmin when combining 93 and 145 GHz. The multiple frequency bands will allow the CMB to be separated from galactic foregrounds (primarily synchrotron and dust), with the primary science goal of characterizing the primordial tensor-to-scalar ratio, r, at a target level of \(\sigma (r) \approx 0.003\).
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Notes
The primordial B-mode has a second peak at \(\ell \lesssim 10\) corresponding to the epoch of reionization. These very large angular scales are not typically accessible from the ground, although this peak is a primary science target of possible upcoming CMB satellites, including the recently selected JAXA-led LiteBIRD satellite [10], and the ground-based CLASS [11] and GroundBIRD [12] experiments.
A more detailed discussion of the opportunistic scheduler can be found in Stevens et al. [21].
Manufactured by Criotec Impianti S.p.A., Chivasso, Italy.
Bluefors Cryogenics, Helsinki, Finland.
Cryomech Inc., Syracuse, NY.
We note here that the LPE’s are not band defining filters; band definition takes place via on-chip filtering integrated into the detector circuit.
Material A4K, shields manufactured by Amuneal Corp., Philadelphia, PA.
The magnetic shielding strategy will be discussed at greater length in an upcoming publication.
Designed and manufactured by Vertex Antennentechnik GmbH, Duisburg, Germany.
Consistent with the realized performance of the POLARBEAR and ACT experiments.
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This work was supported in part by a grant from the Simons Foundation (Award # 457687.)
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Ali, A.M., Adachi, S., Arnold, K. et al. Small Aperture Telescopes for the Simons Observatory. J Low Temp Phys 200, 461–471 (2020). https://doi.org/10.1007/s10909-020-02430-5
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DOI: https://doi.org/10.1007/s10909-020-02430-5