The Simons Observatory: instrument overview

Abstract

The Simons Observatory (SO) will make precision temperature and polarization measurements of the cosmic microwave background (CMB) over angular scales between 1 arcminute and tens of degrees using over 60,000 detectors and sampling frequencies between 27 and 270 GHz. SO will consist of a six-meteraperture telescope coupled to over 30,000 detectors and an array of half-meter aperture refractive cameras, coupled to an additional 30,000+ detectors. The unique combination of large and small apertures in a single CMB observatory will allow us to sample a wide range of angular scales over a common survey area while providing an important stepping stone towards the realization of CMB-Stage IV. CMB-Stage IV is a proposed project that will combine and expand on existing facilities in Chile and Antarctica to reach the 500,000 detectors required for CMB-Stage IV's science objectives. SO and CMB-Stage IV will measure fundamental cosmological parameters of our universe, constrain primordial fluctuations, find high redshift clusters via the Sunyaev-Zeldovich effect, constrain properties of neutrinos, and trace the density and velocity of the matter in the universe over cosmic time. The complex set of technical and science requirements for SO has led to innovative instrumentation solutions which we will discuss. For instance, the SO large aperture telescope will couple to a cryogenic receiver that is 2.4 m in diameter and 2.4 m long. We will give an overview of the drivers for and designs of the SO telescopes and cameras as well as the current status of the project. We will also discuss the current status of CMB-Stage IV and important next steps in the project's development.

Geometrical and physical optics analysis for mm-wavelength refractor telescopes designed to map the cosmic microwave background

“…Unfortunately, in most cases the telescope f -number grows with field location and therefore Equation 4 can only be taken as approximate. Nevertheless, Figure 1 shows the telescope solid angle for a family of f -number curves as a function of r. We compare these curves against the utilized solid angle for the BICEP2/SPIDER [12,17], BICEP3 [18], and Simons Observatory Small Aperture Telescope [6]. The BICEP2/SPIDER telescope was first deployed in 2010, the BICEP3 telescope in 2015, and the Simons Observatory SAT telescope is expected to deploy in 2021.…”

“…Because of these approximating assumptions and the simple nature of the optical system, the PO simulations are sufficiently fast that they can be generated for hundreds of mm-wavelength detectors in a reasonable amount of time (few days) on a workstation computer. 6 The resultant electric field can then be decomposed along an arbitrary vector basis in both the near and the far-field of the instrument.…”

“…The two telescopes that are discussed in this paper, the HDPE and silicon designs, are shown with star-and triangle-shaped markers, respectively. Three existing refractor telescope designs are also shown [6,12,17,18]. For those three telescope designs, we only show the solid angle that is covered by the experiment, not the diffraction-limited solid angle (although those can be very similar).…”

Characterization of Transition Edge Sensors for the Simons Observatory

“…The Simons Observatory collaboration is building a series of telescopes to measure the CMB radiation; one large aperture (∼6m) telescope and three small aperture (∼0.5 m) telescopes [1]. Each Simons Observatory telescope will use arrays of TES bolometers to measure power from the CMB at multiple frequencies.…”

Demonstration of the broadband half-wave plate using the nine-layer sapphire for the cosmic microwave background polarization experiment

“…[2][3][4][5] Upcoming experiments also plan to employ a similar system. [6][7][8][9] The HWP is made of a birefringent material plate with an optic axis parallel to the surface. When the thickness of the plate is chosen properly, the phase difference between the ordinary and extraordinary electric waves passing through the plate becomes π radians, i.e., a half wavelength.…”