SPT: South Pole Telescope

Link to SPT Web site

I. General project/facility description

1. Overview of the facility/project
   The 10 meter South Pole Telescope is being constructed for deployment at the NSF South Pole research station beginning in 2007 November with observations slated to start in 2007 March. The telescope is optimized for conducting large-area millimeter and sub-millimeter wave surveys. In particular, the telescope's off-axis design and careful shielding from contaminating ground emission is ideally suited for measurements of faint, low contrast emission, such as required to map primary and secondary anisotropies in the cosmic microwave background. The full 10 meter diameter projected aperture and the associated optics will have a combined surface accuracy of better than 20 microns rms to allow precision operation in the submillimeter atmospheric windows. The telescope will be surrounded with a large reflecting ground screen to reduce sensitivity to thermal emission from the ground and local interference. The optics of the telescope will support a degree field of view wavelength and initially will feed a 1000-element micro-lithographed planar bolometric array with superconducting transition-edge sensors and frequency-multiplexed readouts.
   The SPT fulfills the recommendation of the AASC report for a South Pole Submillimeter-wave Telescope: "For its combination of low opacity and stable seeing, the South Pole is the best site in the world for ground-based observations at submillimeter wavelengths. To take advantage of the opportunities offered by this site, the committee recommends the construction there of a 7- to 10-m-class filled-aperture submillimeter-wave telescope. Such a telescope should be equipped to survey the sky so that it can identify sources such as primordial galaxies, study the distortion of the cosmic microwave background caused by clusters of galaxies [the Sunyaev-Zel'dovich Effect], and survey the dusty universe." Due to its large aperture and high sensitivity, the South Pole Telescope (SPT) will provide a unique and important new window on the Universe. The expected lifetime of the telescope is of order 20 years.
   The first key project will be to conduct a survey over 4000 square degrees for galaxy clusters using the Sunyaev-Zel'dovich Effect. This survey should find many thousands of clusters with a mass selection criteria that is remarkably uniform with redshift. Armed with redshifts obtained from optical and infrared follow-up observations, it is expected that the survey will enable significant constraints to be placed on the equation of state of the dark energy.
   The maps resulting from the SZE survey will enable powerful studies in many fields, from fine-scale Cosmic Microwave Background (CMB) anisotropy studies (e.g., to measure the higher order acoustic peaks in the angular power spectrum and to extract the lensing signature and other secondary effects), to galaxy surveys and Galactic structure studies. The map will be made publicly available one year after the survey is complete.

2. Managing institution and organization
   The SPT and initial bolometric array receiver is being constructed by a collaboration of five institutions: the University of Chicago, the University of California at Berkeley, Case Western Reserve University, the University of Illinios at Urbana-Champaign and the Smithsonian Astrophysical Observatory. The project is led by the University of Chicago. J. Carlstrom is the Director and S. Padin in the overall project manager. U. Chicago is responsible for the project and is leading the deployment of the telescope. The construction of the initial bolometric receiver is being led by W. Holzapfel and A. Lee at U.C. Berkeley. SAO and CWRU are responsible for optics and UIUC is responsible for pursuing the complementary observations for the initial SZE survey.
   The PI's at all institutions form a Project Committee that oversees the project. They have weekly telecons and meet face to face at least twice per year. An inter-institutional board is planned to deal with any collaboration issues. An external advisory board consisting of eight experts reviews the project yearly in a face to face meeting. They are often consulted when needed. Their reports are forwarded to NSF-OPP. NSF-OPP also requires detailed progress and financial reports every six months as well as a yearly summary report.

3. Funding source(s)
   The project is funded by the Office of Polar Programs (OPP) at the NSF. The 5 year grant to build and deploy the telescope and initial array receiver is $17.7M. Additional resources of the order of 4 FTEs are provided by U. Chicago and U.C. Berkeley. U. Chicago is also providing an additional $1M to seed development of a polarimeter for a second generation SPT instrument. NSF-OPP provides logistical support for the deployment and operation of the telescope. The large ground shields and modifications to the observatory building are being conducted by NSF's contractor Raythen Polar Support Corporation at a cost of an additional ~$4M.
   The current NSF-OPP grant will end in 2007 during the first year of observations. It is expected that NSF-OPP will renew the project with five year grants awards based on peer reviewed proposals submitted by the collaboration.

4. Construction history and cost
   The telescope will be deployed within a kilometer of the geographic south pole at the NSF Amundsen-Scott South Pole Research Station. The laboratory building for the SPT (and other astrophysics projects) will be ready for occupancy in 2006. The snow foundation has been prepared for the telescope and the large "float" foundation structure has been designed and shipped to Antarctica to be installed next year. The telescope is currently being fabricated. It will be test built and tested in Texas during 2006 Summer and shipped to Antarctic in 2006 Fall. The large ground shield will be installed in the season following starting 2007 Fall. First light for the telescope is schedule for January 2007 with observations throughout Austral winter 2007.

5. Operational history and cost
   Future facility:
   Routine operation of the telescope without the ground shield is scheduled for 2007, with the ground shield in 2008. A proposal to NSF-OPP for operations, science support and new instrumentation will be submitted in 2007 June.

II. Technical details

1. Specifics of telescope/instrument
   See (astro-ph/0411122)
   • Optics:
     • Clear 10 meter diameter off-axis paraboloid, projected aperture. Surface accuracy 20µ rms or better over entire surface.
     • Cold (10 K) Gregorian secondary with cold-load baffled enclosure to serve as a cold Lyot stop. The simple cold optics ensures an extremely efficient optical system.
     • Field of view: 1 square degree at 2mm
     • Resolution 9 arcsec FWHM at 350µ, 1 arcmin at 2 mm
     • Inner shields that move with the telescope will deflect rays from the sides of the telescope and the secondary support arm to the cold sky.
     • Large stationary shields will deflect rays from the horizon to the cold sky.
   • Bands:
     • Initial 1000 element bolometric focal plane will be configurable with up to five bands, 90, 150, 220, 270, and 350 GHz.
     • Future instruments are expected to cover the atmospheric windows from 90 to 1500 GHz.
   • Site:
     • location 90 deg South
     • typical precipitable water vapor: 250µ (winter)
     • typical temperature: -60C (winter)
     • extremely stable atmosphere
     • sources do not rise or set (observed at constant air-mass)

2. New capabilities anticipated/planned in next 5-10 years
   A powerful, next technology mm/submm, monolithic, planar antenna-coupled bolometric polarimeter is being planned. Seed money has been acquired. The earliest deployment would be 2008 November.
   Coherent and incoherent focal plane arrays for surveying for a variety of science projects has been discussed, e.g., mapping star forming regions, nearby galaxies, and searching for early dusty galaxies.
   The SPT is also expected to serve as a finder telescope for ALMA.

III. User profile

1. % of "open skies" time
   

2. Institutional affiliations of users
   The SPT will serve the community through conducting large surveys. The survey data will be made publicly available. Future instruments may also be built and deployed by new groups from the community.

3. Student access, involvement, usage
   

IV. Science Overview

1. Current forefront scientific programs
   Future facility: NA.

2. Major discoveries (through 1999)
   Future facility: NA.

3. Science highlights of last 5 years
   Future facility: NA.

4. Main future science questions to be addressed
   The initial thrust of the SPT project is to pursue cosmological studies by chararterizing the CMB, as detailed below. An by-product of these studies will be a complete flux limited catalog of radio and dusty galaxies. Future coherent and incoherent arrays on the telescope will allow surveys for line emission from galactic and extragalactic sources and complete mm/submm spectral energy distributions. The South Pole site will also allow limited observations in the 200µ window.
   The initial key science to be pursued with the SPT is the characterization of the fine scale temperature and polarization anisotropy of the cosmic microwave background radiation (CMB). Remarkable progress has been made in this field over the last several years. It was nearly 30 years after the initial discovery of the CMB by Penzias and Wilson in 1965 before small differences in its intensity were measured by COBE and its spectrum was shown to be a blackbody to high precision. The remarkable isotropy, precise to a part in 100,000, helped motivate the inflation theory for the origin of the universe. In the past few years, subsequent measurements of the first acoustic peak and its harmonics in the angular power spectrum provided further support for inflation by showing the curvature of the universe was flat. They also allowed a full accounting for the matter-energy densities of the universe, finding in agreement with the analysis of Type 1a supernovae observations that the universe is now dominated by some sort of "dark energy" that apparently is causing the expansion of the universe to accelerate. More recently the WMAP satellite has produced spectacular all sky maps of the temperature anisotropy yielding a highly precise measurement of the angular power spectrum up to multipoles of 600, corresponding to an angular scale of ~20 arc minutes. The WMAP data, especially combined with finer angular scale CMB anisotropy measurements made with ACBAR and CBI and with other probes of large scale structure have provided a high degree of confidence in the now standard cosmological model and allowed tight constraints to be placed on many of its parameters.
   While these measurements have led to rapid progress in our understanding of the universe, they have raised even more profound questions about the nature of dark energy and of the possibility of directly testing inflation and determining its energy scale. Remarkably, these questions can be addressed through future measurements of the CMB temperature anisotropy on fine angular scales and of the CMB polarization anisotropy on all angular scales; they form the basis of the scientific case for the initial CMB studies planned for the South Pole Telescope program.
   Finer angular scale temperature anisotropy measurements are needed to precisely measure the angular power spectrum through the damping tail. Such observations will lead to better parameter constraints and in particular allow a better characterization of the underlying primordial matter power spectrum, that in principle can be used to constrain inflationary models. On angular scales of a few arcminutes and smaller, i.e., multipoles exceeding ~2000, the CMB anisotropy is dominated by secondary effects caused by distortions of the CMB as it passes through the universe. The largest such effect is the Sunyaev-Zeldovich Effect (SZE), in which the CMB photons are inverse Compton scattered by the hot intracluster gas of galaxy clusters. The SZE is a potentially powerful probe of cosmology. Perhaps its most powerful use will be to enable large area, redshift independent surveys for galaxy clusters. As the growth of massive clusters is critically dependent on the underlying cosmology, the yields from such surveys can be used to set tight constraints on cosmological parameters and to investigate the nature of dark energy, i.e., by determining its equation of state.
   Measurements of the polarization of the CMB are extremely challenging, but also have the enormous potential for discovery. The intrinsic polarization of the CMB reflects the local radiation field anisotropy, specifically the local quadrupole moment of the incident radiation field, at the surface of last scattering 14 billion years ago. The dominant contribution is due to Doppler shifted radiation fields arising from the acoustic oscillations at the time of last scattering. This causes the so called E-mode polarization (curl free polarization patterns on the sky) and was first detected by DASI and now CBI and CapMap, while the temperature-polarization cross power spectrum (TE) has been detected by DASI and WMAP. However, if inflation occurred in the early universe at a high-enough energy scale, a portion of the local quadrupole at last scattering will be due to primordial gravitational waves created during the inflationary epoch. The inflationary gravitational waves will cause both E-mode and B-mode (curl component) polarization patterns in the CMB. While the B-mode pattern can be distinguished from the intrinsic E-mode pattern, the gravitational lensing of the CMB by large scale structure in the universe will create B-mode polarization from the intrinsic E-mode signal at a level that is higher than the inflationary B-modes for all but the most optimistic inflationary models. In this case, the only hope in recovering the inflationary B-modes from the lensing B-mode foreground lies in exploiting the different angular power spectra and their correlations with the temperature and E-mode spectra. The lensing polarization signal is also interesting in its own right as it can be used to trace the growth of large scale structure which in turn is sensitive to the mass of the neutrino and the equation of state of the dark energy.

5. Synergies with other major forefront facilities
   The ability to conduct, high resolution, large area surveys through the millimeter and sub-millimeter bands is an important complement to radio, Far-IR, IR, optical, UV, x-ray and high energy surveys. The results of the millimeter and submm surveys will also serve as finder charts for the upcoming ALMA telescope.

6. Unique contributions
   The South Pole Telescope (SPT), is being designed to pursue initially these next generation CMB temperature and polarization studies at the exceptional South Pole site. The telescope is designed explicitly for conducting large area, high sensitivity survey observations of the temperature and polarization of the CMB.

V. Education/Outreach activities

1. Visitor facility
   Future facility:NYA
   Most of the current EPO activities of the SPT are not centralized. They include the development and implementation of an undergraduate laboratory for measuring the temperature of the CMB. At Chicago well over 1000 non-science majors have performed this hands-on laboratory in freshman classes. We have developed and use a 4.5 m educational telescope for measuring Galactic HI and continuum emission in undergraduate laboratory.
   The SPT collaboration is currently investigating mechanisms to implement a project-wide education and outreach project once the current construction phase of the project is complete.

2. Student programs
   At all five institutions, post doctoral, graduate and undergraduate education and research is integrated in the construction of the instrumentation as well as in the analysis of the data. There have been 6 postdocs, 13 graduate students, and 7 undergraduate students involved in the project. Unlike most large facilities, graduate and undergraduate students play a major role in all aspects of the project, exposing them to all aspects of scientific and engineering research. They are learning valuable skills which will aid them in pursuing their careers, whether in industry or academia.
   We do believe that the active participation and training of future scientist in the project at this stage is a major contribution of the SPT to the development of human resources.

3. Other (as apply)
   

VI. Documentation/website URLs

1. URL of facility website
   Web site in construction:

2. URL of EPO website
   
3. URL(s) of any brief overviews of project/facility
   
4. URL(s) of miscellaneous documentation
   Please see: "The South Pole Telescope" J.E. Ruhl, P.A.R. Ade, J.E. Carlstrom, H.M. Cho, T. Crawford, M. Dobbs, C.H. Greer, N.W. Halverson, W.L. Holzapfel, T.M. Lanting, A.T. Lee, J. Leong, E.M. Leitch, W. Lu, M. Lueker, J. Mehl, S.S. Meyer, J.J. Mohr, S. Padin, T. Plagge, C. Pryke, D. Schwan, M.K. Sharp, M.C. Runyan, H.Spieler, Z. Staniszewski and A.A. Stark, 2004, SPIE Vol. 5498, p 11-29 (astro-ph/0411122).