The 10 Meter South Pole Telescope

TL;DR

The paper presents the design, implementation, and early performance of the 10 m South Pole Telescope (SPT), a wide-field millimeter-wave observatory optimized for large-area surveys and high-sensitivity CMB measurements. It describes the offset-Gregorian optical layout, a large cold stop, a $10$ m primary, and a cooled $1$ m secondary that together minimize spillover and ground pickup while enabling rapid scanning. The receiver contains a $966$-pixel TES bolometer focal plane across $3$, $2$, and $1.3$ mm bands, with a frequency-m multiplexed SQUID readout and cryogenic architecture delivering background-limited sensitivity; the telescope achieves precise pointing with metrology and star-based calibration, and robust operation in the harsh South Pole environment. The results include the first SZ-detected clusters, a catalog from SZ-selected clusters, measurements of the high-$\ell$ CMB power spectrum, and plans for a subsequent polarimeter to constrain dark energy, neutrino masses, and inflationary energy scales, highlighting the instrument’s significance for cosmology and future mm-wave surveys.

Abstract

The South Pole Telescope (SPT) is a 10 m diameter, wide-field, offset Gregorian telescope with a 966-pixel, multi-color, millimeter-wave, bolometer camera. It is located at the Amundsen-Scott South Pole station in Antarctica. The design of the SPT emphasizes careful control of spillover and scattering, to minimize noise and false signals due to ground pickup. The key initial project is a large-area survey at wavelengths of 3, 2 and 1.3 mm, to detect clusters of galaxies via the Sunyaev-Zeldovich effect and to measure the small-scale angular power spectrum of the cosmic microwave background (CMB). The data will be used to characterize the primordial matter power spectrum and to place constraints on the equation of state of dark energy. A second-generation camera will measure the polarization of the CMB, potentially leading to constraints on the neutrino mass and the energy scale of inflation.

Figures (14)

• Figure 1: The 10 meter South Pole Telescope (SPT).
• Figure 2: SPT optics details for (top) the basic Gregorian telescope with no lens and (bottom) a meniscus lens that makes the final focus telecentric and gives more uniform illumination of the secondary. For each surface, $r$ is the radius of curvature and $k$ is the conic constant. Dimensions are in mm at the operating temperature (ambient for the primary, 10 K for the secondary and 4 K for the lens).
• Figure 3: Section through the receiver and optics cryostats.
• Figure 4: Optical bench assembly. This view is looking up into the receiver cabin from the control room. The sky end of the cabin is at the top. The optics cryostat is the large, white, cylindrical vessel in the center of the picture and the optical bench is the white frame around it. The receiver (with many wires running down to the readout electronics) is just below center. Three of the 6 optical bench actuators are visible at the top, left and right of the picture. The other 3 actuators connect the corners of the bench to the cabin roof.
• Figure 5: Primary surface profile errors. The greyscale range is $+75$$\mu$m (white) to $-75$$\mu$m (black). The features at the bottom are artifacts caused by reflections from the L frame where the beam enters the receiver cabin near prime focus. Light (i.e., high) stripes along the panel edges are due to the gap covers. The surface error (with uniform weighting over the entire primary) is 20 $\mu$m rms.