QUIET: The Q/U Imaging Experiment

Link to QUIET web site (under construction)

I. General project/facility description

1. Overview of the facility/project
   The Q/U Imaging Experiment (QUIET) is a 5-year program to measure the polarization of the CMB with accuracy near the limit of what is possible from the ground. QUIET uses novel MMIC and millimeter-wave circuit packaging technology developed by Todd Gaier and Mike Seiffert at JPL to enable the affordable construction of large array cameras of coherent detectors at microwave frequencies. The QUIET project proposes to install 40 GHz and 90 GHz cameras on 2-m (1-m in the prototype Phase I) and 7-m diameter telescopes located at the 5080-m altitude Atacama Science Preserve site in Chile (home of ALMA). QUIET will image polarization on angular scales from a few arcminutes to a few degrees, and will eventually cover approximately 160 square degrees at 0.1 degree resolution and 1600 square degrees at 1 degree resolution. Phase I of QUIET is proceeding with NASA/Caltech funding and will consist of smaller prototype arrays with ~100 feeds, while Phase II will field ~1000 feeds (proposal pending). The QUIET technology is optimized for ground-based observations from a high and dry site at frequencies below 100 GHz (at expected foreground contamination minimum), where coherent amplifier arrays provide significant advantages for polarimetry over bolometer arrays. The ground-based approach to imaging smaller areas of the sky with high sensitivity per pixel is also complementary to the full-sky space-based approach of wider more-shallow surveys, and allows the fielding of multiple experiments with different characteristics at a fraction of the cost.
   The primary science goals of QUIET are the measurement of the E-mode and B-mode polarized anisotropies in the CMB, with the ultimate goal of detecting the B-modes from inflation. For example, in Phase I QUIET will be able to make a 5-sigma detection of gravity waves for a T/S > 0.16 (tensor-to-scalar ratio, depends on the energy scale of inflation in standard models), and in the proposed Phase II for T/S > 0.009. QUIET will also measure the larger signal due to gravitational lensing of the CMB by the cosmic web of large-scale structure. QUIET will also provide measurements of the EE intrinsic CMB power spectrum at unprecedented sensitivity levels, enabling careful tests of the standard model such as the level of non-adiabatic fluctuations (e.g. isocurvature modes) or the possibility of low-level broken scale invariance of the power spectrum. Finally, QUIET will characterize the level of polarized foreground emission from our galaxy (it will have to deal with this to do its science) and will complement other high-sensitivity programs such as those proposed for ACT, SPT, LSAT and ALMA in fully understanding the sub-mK diffuse galactic emission fluctuations.
   As single detectors have performance near the quantum limit, the only way to reach the required CMB sensitivity levels is to build large arrays (coherent array cameras, bolometer cameras, or large interferometers!). At the sensitivity levels of B-mode CMB polarization, characterization and control of systematic is critical to a successful experiment, and the coherent cross-correlation technology of QUIET provides a complementary approach to other bolometer-based experiments. Furthermore, the breakthroughs in millimeter/microwave packaging achieved in the development of these detectors are making arbitrarily large coherent arrays available for other radio and millimeter-wave astronomy projects at modest cost (several groups are currently pursuing obtaining focal plane arrays based on the QUIET design). These arrays would be ideal for spectroscopic survey cameras, for instance.

2. Managing institution and organization
   
   • Jet Propulsion Laboratory (JPL): primary NASA institution
   • U. Chicago: primary NSF institution.
   • Collaborating institutions: U.C. Berkeley, Caltech, Columbia U., Goddard Space Flight Center, Harvard/SAO, U. Miami, Princeton

3. Funding source(s)
   
   • NASA: ~20% (including ~4-5% JPL discretionary funds)
   • NSF:~75%
   • Caltech + other institutions ~5%

4. Construction history and cost
   
   • Phase I (funded)
     • Apr 2005: 7-element Demonstrator Array (DA)
     • Jun 2005: 1-m telescope (same as 2-m design) mounted on CBI platform
     • Dec 2005: 91-element camera at 90 GHz (W1)
     • Apr 2006: 19-element camera at 40 GHz (Q1)
   • Phase II (proposal pending, dates contingent on funding for QUIET as well as CBI operations)
     • Jul 2005: 1-m DA observations
     • Jan 2006: 1-m WA observations
     • Mar 2006: 2-m telescope (#1) on CBI (new top platform)
     • Dec 2006: 7-m (Crawford Hill?) telescope move to Chile completed
     • Jun 2007: 397-element camera at 90 GHz (W2)
     • Mar 2008: 2-m telescope (#2)
     • Jun 2008: 91-element camera at 40 GHz (Q2)
     • Nov 2008: 91-element camera at 40 GHz (Q3)
     • Dec 2008: 2-m telescope (#3)
     • Jan 2009: 397-element camera at 90 GHz (W3)

   • Total cost: ~$25M of which ~$19M is expected/requested from NSF

5. Operational history and cost
   Future facility: NA.

II. Technical details

1. Specifics of telescope/instrument
   
   • large format coherent array cameras (MMIC technology)
   • 40 GHz (8 GHz BW) and 90 GHz (18 GHz BW)
   • Tsys 27K (40 GHz) and 54K (90 GHz)
   • correlation polarimeters
   • 3 x 2-m telescopes plus one 7-m
   • at 5080m Atacama site in Chile
   • P2 Q+U sensitivity (per feed in 1s) 0.16 mK (40 GHz), 0.25 mK (90 GHz)
   • P2 Q+U sensitivity (per 1deg pixel over 1600 sq.deg) 85 nK (90 GHz)
   • P2 Q+U sensitivity (per 0.1deg pixel over 160 sq.deg) 290 nK (90 GHz)

2. New capabilities anticipated/planned in next 5-10 years
   Future facility.

III. User profile

1. % of "open skies" time
   Probably none (targeted experiment)

2. Institutional affiliations of users
   Current participants come from JPL, Caltech, Princeton, Chicago, GSFC, U. Miami, Columbia, and U.C. Berkeley.

3. Student access, involvement, usage
   Students from participating universities will be involved in QUIET.

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
   
   • constraints on or detection of CMB intrinsic BB polarization signature due to gravity waves from inflation
   • measurement of BB polarization signature of large-scale structure due to weak gravitational lensing of CMB
   • measurement of CMB EE polarization for improved cosmological parameter constraints and check of the "Standard Model"
   • characterization of galactic & extragalactic polarized microwave foregrounds at 0.1mK levels on 0.1/1 deg scales

5. Synergies with other major forefront facilities
   
   • complements space-based CMB polarization mission (Beyond Einstein).
   • complements higher-frequency ground-based bolometer CMB experiments.
     Frequency and angular scale coverage critical to foreground characterization and removal for all programs - QUIET is part of an ambitious suite of experiments.
   • studies of the BB polarization due to gravitational lensing will involve measurement of the large scale structure in the optical and IR bands and the redshifts of clusters and filaments.

6. Unique contributions
   Targeted experiment. See above.

V. Education/Outreach activities

1. Visitor facility
   NA

2. Student programs
   See above. Students from participating universities will be involved.

3. Other (as apply)
   Future facility: EPO plan included in NSF proposal.

VI. Documentation/website URLs

1. URL of facility website
   http://quiet.uchicago.edu/ (under construction, not yet available)

2. URL of EPO website
   Future facility: NYA

3. URL(s) of any brief overviews of project/facility
   See Charles Lawrence presentation posted at: http://www.aoc.nrao.edu/~smyers/cbi/pdftalks/QUIET-Moscow.pdf