QUIET was an

astronomy Astronomy is a natural science that studies celestial objects and the phenomena that occur in the cosmos. It uses mathematics, physics, and chemistry in order to explain their origin and their overall evolution. Objects of interest includ ...

experiment An experiment is a procedure carried out to support or refute a hypothesis, or determine the efficacy or likelihood of something previously untried. Experiments provide insight into cause-and-effect by demonstrating what outcome occurs whe ...

to study the polarization of the

cosmic microwave background radiation The cosmic microwave background (CMB, CMBR), or relic radiation, is microwave radiation that fills all space in the observable universe. With a standard optical telescope, the background space between stars and galaxies is almost completely dar ...

. QUIET stands for Q/U Imaging ExperimenT. The Q/U in the name refers to the ability of the telescope to measure the Q and U

Stokes parameters The Stokes parameters are a set of values that describe the Polarization (waves), polarization state of electromagnetic radiation. They were defined by George Gabriel Stokes in 1851, as a mathematically convenient alternative to the more common de ...

simultaneously. QUIET was located at an elevation of 5,080

metre The metre (or meter in US spelling; symbol: m) is the base unit of length in the International System of Units (SI). Since 2019, the metre has been defined as the length of the path travelled by light in vacuum during a time interval of of ...

s (16,700 feet) at

Llano de Chajnantor Observatory Llano de Chajnantor Observatory is the name for a group of astronomy, astronomical observatory, observatories located at an altitude of over 4,800 m (15,700 ft) in the Atacama Desert of northern Chile. The site is in the Antofagasta Reg ...

in the

Chile Chile, officially the Republic of Chile, is a country in western South America. It is the southernmost country in the world and the closest to Antarctica, stretching along a narrow strip of land between the Andes, Andes Mountains and the Paci ...

Andes The Andes ( ), Andes Mountains or Andean Mountain Range (; ) are the List of longest mountain chains on Earth, longest continental mountain range in the world, forming a continuous highland along the western edge of South America. The range ...

. It began observing in late 2008 and finished observing in December 2010. QUIET was the result of an international collaboration that had its origins in the

CAPMAP CAPMAP is an experiment at Princeton University to measure the polarization of the cosmic microwave background. See also *Cosmic microwave background experiments *Observational cosmology Observational cosmology is the study of the structure, the ...

Cosmic Background Imager The Cosmic Background Imager (or CBI) was a 13-element astronomical interferometer perched at an elevation of 5,080 metres (16,700 feet) at Llano de Chajnantor Observatory in the Chilean Andes. It started operations in 1999 to study the cosmi ...

(CBI) and

QUaD QUaD, an acronym for QUEST at DASI, was a ground-based cosmic microwave background (CMB) polarization experiment at the South Pole. QUEST (Q and U Extragalactic Sub-mm Telescope) was the original name attributed to the bolometer detector instrume ...

collaborations. The collaboration consisted of 7 groups in the

United States The United States of America (USA), also known as the United States (U.S.) or America, is a country primarily located in North America. It is a federal republic of 50 U.S. state, states and a federal capital district, Washington, D.C. The 48 ...

(the

California Institute of Technology The California Institute of Technology (branded as Caltech) is a private research university in Pasadena, California, United States. The university is responsible for many modern scientific advancements and is among a small group of institutes ...

, the

University of Chicago The University of Chicago (UChicago, Chicago, or UChi) is a Private university, private research university in Chicago, Illinois, United States. Its main campus is in the Hyde Park, Chicago, Hyde Park neighborhood on Chicago's South Side, Chic ...

Columbia University Columbia University in the City of New York, commonly referred to as Columbia University, is a Private university, private Ivy League research university in New York City. Established in 1754 as King's College on the grounds of Trinity Churc ...

, the

Jet Propulsion Laboratory The Jet Propulsion Laboratory (JPL) is a Federally funded research and development centers, federally funded research and development center (FFRDC) in La Cañada Flintridge, California, Crescenta Valley, United States. Founded in 1936 by Cali ...

, the

University of Miami The University of Miami (UM, UMiami, Miami, U of M, and The U) is a private university, private research university in Coral Gables, Florida, United States. , the university enrolled 19,852 students in two colleges and ten schools across over ...

Princeton University Princeton University is a private university, private Ivy League research university in Princeton, New Jersey, United States. Founded in 1746 in Elizabeth, New Jersey, Elizabeth as the College of New Jersey, Princeton is the List of Colonial ...

and

Stanford University Leland Stanford Junior University, commonly referred to as Stanford University, is a Private university, private research university in Stanford, California, United States. It was founded in 1885 by railroad magnate Leland Stanford (the eighth ...

), 4 groups in

Europe Europe is a continent located entirely in the Northern Hemisphere and mostly in the Eastern Hemisphere. It is bordered by the Arctic Ocean to the north, the Atlantic Ocean to the west, the Mediterranean Sea to the south, and Asia to the east ...

(the

University of Manchester The University of Manchester is a public university, public research university in Manchester, England. The main campus is south of Manchester city centre, Manchester City Centre on Wilmslow Road, Oxford Road. The University of Manchester is c ...

, the Max-Planck-Institut für Radioastronomie Bonn, the

University of Oslo The University of Oslo (; ) is a public university, public research university located in Oslo, Norway. It is the List of oldest universities in continuous operation#Europe, oldest university in Norway. Originally named the Royal Frederick Univ ...

and the

University of Oxford The University of Oxford is a collegiate university, collegiate research university in Oxford, England. There is evidence of teaching as early as 1096, making it the oldest university in the English-speaking world and the List of oldest un ...

) and one group in

Japan Japan is an island country in East Asia. Located in the Pacific Ocean off the northeast coast of the Asia, Asian mainland, it is bordered on the west by the Sea of Japan and extends from the Sea of Okhotsk in the north to the East China Sea ...

(

KEK , known as KEK, is a Japanese organization whose purpose is to operate the largest particle physics laboratory in Japan, situated in Tsukuba, Ibaraki prefecture. It was established in 1997. The term "KEK" is also used to refer to the laboratory ...

; the first time a Japan group has been involved in CMB studies). Other members of the collaboration are from the

University of California, Berkeley The University of California, Berkeley (UC Berkeley, Berkeley, Cal, or California), is a Public university, public Land-grant university, land-grant research university in Berkeley, California, United States. Founded in 1868 and named after t ...

, the

Goddard Space Flight Center The Goddard Space Flight Center (GSFC) is a major NASA space research laboratory located approximately northeast of Washington, D.C., in Greenbelt, Maryland, United States. Established on May 1, 1959, as NASA's first space flight center, GSFC ...

and the Center for Astrophysics Harvard & Smithsonian.

Instrument

QUIET had arrays of detectors at two frequencies: 43

GHz The hertz (symbol: Hz) is the unit of frequency in the International System of Units (SI), often described as being equivalent to one event (or Cycle per second, cycle) per second. The hertz is an SI derived unit whose formal expression in ter ...

(

Q band The Q band is a range of frequencies contained in the microwave region of the electromagnetic spectrum. Common usage places this range between 33 and 50 GHz, but may vary depending on the source using the term. The foregoing range corresponds ...

) and 95 GHz (

W band The W band of the microwave part of the electromagnetic spectrum ranges from 75 to 110 GHz, wavelength ≈2.7–4 mm. It sits above the U.S. IEEE-designated V band (40–75 GHz) in frequency, and overlaps the NATO designated M ba ...

). It used four telescopes, three of which were purpose-built 2 m types with the other being the 7 m Crawford Hill telescope used for

. As a result, it had

angular resolution Angular resolution describes the ability of any image-forming device such as an Optical telescope, optical or radio telescope, a microscope, a camera, or an Human eye, eye, to distinguish small details of an object, thereby making it a major det ...

s between a few arcminutes and several degrees. The detectors were mass-produced

coherent Coherence is, in general, a state or situation in which all the parts or ideas fit together well so that they form a united whole. More specifically, coherence, coherency, or coherent may refer to the following: Physics * Coherence (physics ...

correlation In statistics, correlation or dependence is any statistical relationship, whether causal or not, between two random variables or bivariate data. Although in the broadest sense, "correlation" may indicate any type of association, in statistics ...

polarimeter A polarimeter is a scientific instrument used to measure optical rotation: the angle of rotation caused by passing linearly polarized light through an Optical activity, optically active substance. Some chemical substances are optically active, ...

s. The instrument was constructed in three phases. The first phase consisted of a 7-element 95 GHz array to demonstrate the technology. The second phase mounted a 91-element 95 GHz array (with 18 GHz

bandwidth Bandwidth commonly refers to: * Bandwidth (signal processing) or ''analog bandwidth'', ''frequency bandwidth'', or ''radio bandwidth'', a measure of the width of a frequency range * Bandwidth (computing), the rate of data transfer, bit rate or thr ...

) and a 19-element 43 GHz array (with 8 GHz bandwidth) on 1.4 m

cassegrain Cassegrain may refer to * Cassegrain reflector, a design used in telescopes * Cassegrain antenna, a type of parabolic antenna * Cassegrain (crater), on the Moon * a Belgian canned vegetables producer now part of Bonduelle S.A. People : * Guillaum ...

telescopes, mounted on what was the CBI platform. It started observing in 2008. The third phase planned four further arrays by 2010. Two of these were at 43 GHz, with 91 elements each, and the other two were at 95 GHz, with 397 elements each. These were mounted on three 2 m dishes on the CBI platform and the 7 m telescope.Samtleben (2008) The instrument was located at a height of 5,080 m at Llano de Chajnantor Observatory in the

. The site is owned by the Chilean government, and is leased to the

Atacama Large Millimeter Array The Atacama Large Millimeter/submillimeter Array (ALMA) is an astronomical interferometer of 66 radio telescopes in the Atacama Desert of northern Chile, which observe electromagnetic radiation at millimeter and submillimeter wavelengths. The ar ...

. The site was selected due to the altitude, infrastructure and accessibility, as well as the low humidity of the site, which reduces the contamination of the detected signals by the atmosphere.

Science

QUIET measured the polarization of the

(CMB). This polarization is commonly split into two components: E-modes, which represent the gradient component, and B-modes, which give the curl component. It is thought that B-modes are formed both from primordial fluctuations due to

cosmic inflation In physical cosmology, cosmic inflation, cosmological inflation, or just inflation, is a theory of exponential expansion of space in the very early universe. Following the inflationary period, the universe continued to expand, but at a slower ...

, and from

gravitational lens A gravitational lens is matter, such as a galaxy cluster, cluster of galaxies or a point particle, that bends light from a distant source as it travels toward an observer. The amount of gravitational lensing is described by Albert Einstein's Ge ...

ing of the CMB. As of 2008, only E-modes have been detected. QUIET aims to detect and characterize the B-modes polarization for the first time, and to provide more accurate measurements of the E-mode polarization. B-modes are thought to be much fainter than E-modes, as they are formed by higher order effects. The ratio of the E-mode to B-mode polarization is currently unknown, and the minimum detectable value of this can be used as a measure of the sensitivity of a CMB instrument. For QUIET this value is r=0.009, which corresponds to the

energy scale This list compares various energies in joules (J), organized by order of magnitude. Below 1 J 1 to 105 J 106 to 1011 J 1012 to 1017 J 1018 to 1023 J Over 1024 J SI multiples See also * Conversion of units of e ...

being around

10^

GeV In physics, an electronvolt (symbol eV), also written electron-volt and electron volt, is the measure of an amount of kinetic energy gained by a single electron accelerating through an electric potential difference of one volt in vacuum. When us ...

. QUIET's measurements of the CMB's

power spectrum In signal processing, the power spectrum S_(f) of a continuous time signal x(t) describes the distribution of Power (physics), power into frequency components f composing that signal. According to Fourier analysis, any physical signal can be ...

were designed to be between the

multipole A multipole expansion is a mathematical series representing a function that depends on angles—usually the two angles used in the spherical coordinate system (the polar and azimuthal angles) for three-dimensional Euclidean space, \R^3. Multipol ...

s of about 40 and 2,500, and will be made in a section of the sky known to have low foreground contamination.

Results

The first season reported on power spectra from over 10000 hours of observation at 43 GHz in the multipole range ℓ = 25–475. The E-mode result was consistent with the

standard cosmological model The Lambda-CDM, Lambda cold dark matter, or ΛCDM model is a mathematical model of the Big Bang theory with three major components: # a cosmological constant, denoted by lambda (Λ), associated with dark energy; # the postulated cold dark matte ...

. A B-mode spectrum was not detected. The second season paper included 95 GHz data. Power spectra from ℓ = 25 to 975 were used to constrain the tensor-to-scalar ratio.

Status

As of March 2011, the QUIET team described the status

Observations were made from October 2008 through May 2009 using a 19-element 40 GHz instrument coupled to a 1.4 meter telescope located at the Llano de Chajnantor Observatory in Chile. Observations with a 91-element 90 GHz instrument on the same telescope finished in December 2010. The QUIET instrument has been dismantled from the old CBI mount.

References

Journal article

* {{DEFAULTSORT:Quiet Cosmic microwave background experiments Astronomical observatories in Chile Buildings and structures in Antofagasta Region