The Simons Observatory (SO) will make precision temperature and polarization measurements of the cosmic
microwave background (CMB) using a series of telescopes which will cover angular scales between 1 arcminute
and tens of degrees, contain over 40,000 detectors, and sample frequencies between 27 and 270 GHz. SO will
consist of a six-meter-aperture telescope coupled to over 20,000 detectors along with an array of half-meter
aperture refractive cameras, coupled to an additional 20,000+ detectors. The unique combination of large and
small apertures in a single CMB observatory, which will be located in the Atacama Desert at an altitude of
5190 m, will allow us to sample a wide range of angular scales over a common survey area. SO will measure
fundamental cosmological parameters of our universe, find high redshift clusters via the Sunyaev-Zeldovich effect,
constrain properties of neutrinos, and seek signatures of dark matter through gravitational lensing. The complex
set of technical and science requirements for this experiment has led to innovative instrumentation solutions
which we will discuss. The large aperture telescope will couple to a cryogenic receiver that is 2.4 m in diameter
and over 2 m long, creating a number of interesting technical challenges. Concurrently, we are designing an array
of half-meter-aperture cryogenic cameras which also have compelling design challenges. We will give an overview
of the drivers for and designs of the SO telescopes and the cryogenic cameras that will house the cold optical
components and detector arrays.
CCAT-prime will be a 6-meter aperture telescope operating from sub-mm to mm wavelengths, located at 5600 meters elevation on Cerro Chajnantor in the Atacama Desert in Chile. Its novel crossed-Dragone optical design will deliver a high throughput, wide field of view capable of illuminating much larger arrays of sub-mm and mm detectors than can existing telescopes. We present an overview of the motivation and design of Prime-Cam, a first-light instrument for CCAT-prime. Prime-Cam will house seven instrument modules in a 1.8 meter diameter cryostat, cooled by a dilution refrigerator. The optical elements will consist of silicon lenses, and the instrument modules can be individually optimized for particular science goals. The current design enables both broad- band, dual-polarization measurements and narrow-band, Fabry-Perot spectroscopic imaging using multichroic transition-edge sensor (TES) bolometers operating between 190 and 450 GHz. It also includes broadband kinetic induction detectors (KIDs) operating at 860 GHz. This wide range of frequencies will allow excellent characterization and removal of galactic foregrounds, which will enable precision measurements of the sub-mm and mm sky. Prime-Cam will be used to constrain cosmology via the Sunyaev-Zeldovich effects, map the intensity of [CII] 158 μm emission from the Epoch of Reionization, measure Cosmic Microwave Background polarization and foregrounds, and characterize the star formation history over a wide range of redshifts. More information about CCAT-prime can be found at www.ccatobservatory.org.
The Simons Observatory (SO) is an upcoming experiment that will study temperature and polarization fluctuations in the cosmic microwave background (CMB) from the Atacama Desert in Chile. SO will field both a large aperture telescope (LAT) and an array of small aperture telescopes (SATs) that will observe in six bands with center frequencies spanning from 27 to 270 GHz. Key considerations during the SO design phase are vast, including the number of cameras per telescope, focal plane magnification and pixel density, in-band optical power and camera throughput, detector parameter tolerances, and scan strategy optimization. To inform the SO design in a rapid, organized, and traceable manner, we have created a Python-based sensitivity calculator with several state-of-the-art features, including detector-to-detector optical white-noise correlations, a handling of simulated and measured bandpasses, and propagation of low-level parameter uncertainties to uncertainty in on-sky noise performance. We discuss the mathematics of the sensitivity calculation, the calculator's object-oriented structure and key features, how it has informed the design of SO, and how it can enhance instrument design in the broader CMB community, particularly for CMB-S4.