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SPT: South Pole Telescope
SPT Web site
I. General project/facility description
- 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
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
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.
- 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.
- 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
- 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.
- Operational history and cost
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
- Specifics of telescope/instrument
- 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.
- 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.
- 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)
- 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
The SPT is also expected to serve as a finder telescope for ALMA.
III. User profile
- % of "open skies" time
- 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.
- Student access, involvement, usage
IV. Science Overview
- Current forefront scientific programs
Future facility: NA.
- Major discoveries (through 1999)
Future facility: NA.
- Science highlights of last 5 years
Future facility: NA.
- 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.
- 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.
- 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
- Visitor facility
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.
- 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.
- Other (as apply)
VI. Documentation/website URLs
- URL of facility website
Web site in construction:
- URL of EPO website
- URL(s) of any brief overviews of project/facility
- 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
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Last modified: Wed Jan 26 11:08:18 AST 2005