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The MissionThe Mission
Explore the Dark Ages through the neutral hydrogen distribution
Constrain the populations of the first stars and first black holes.
Measure density fluctuations in the early universe
Obtain the equation of state of dark energy test alternate theories of gravity
[The first 4 slides are taken from Greg Taylor’s presentation on telescope requirements to LARC/DALI meeting at GSFC in Jan 2009]
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Assumptions Assumptions
Array to be located on the Far Side of the Moon Minimizes terrestrial RFI Minimizes Ionospheric Fluctuations
Observe during the Lunar night (50% duty cycle) Minimizes solar RFI
Array to consist of N stations, each with M dipole pairs
Each station will be capable for forming B beams on the sky
Array assumed to be deployed in a locally flat region
Array is to be deployed robotically
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Scientific Requirements Scientific requirements Redshift range: z=50 to 6 Angular resolution: 1.4’ Bandwidth: 8 MHz Sensitivity in 1000 h at z=15:
0.2 microJy/beam Brightness Sensitivity: 4 milliK FOV: 11 sq deg Dual Circular Dynamic range: 106 to 107
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Technical Requirements Technical requirements Frequency range: 30 - 200 MHz Collecting area: 3.0 km2
Maximum baseline: 10 km Bandwidth: 8 MHz Station Diameter: 150 m
Number of Stations: 300 Number of Beams: 9 Dipole pairs in each station: 1500
Antenna FOV: 45 deg FWHM
Ground-based reionization experiments
Science Goals of the Murchison Widefield Array
• Epoch of Reionization• Heliospheric Physics• Astronomical transients
Sited in Western AustraliaMIT Haystack Observatory
MIT Kavli InstituteHarvard-Smithsonian Center for AstrophysicsAustralia National UniversityMelbourne University + consortiumRaman Research Institute
Chippendale & Beresford 2007
Antenna tile 32 antenna tiles
26-tile MWA image Simulation
Imaging by R. Wayth
Current Phase is MWA “Demonstrator”(under construction)
N=512; D=4m - LARGE etendue; good foreground subtraction
Digitized at antenna (660 Msamples/sec) - direct conversion
Raw data rate = 512 X 2 X 660MHz X 10 bits = 844 GB/sec
After digital filters and correlator: 20 GB/sec (32 MHz bandwidth; 2 Gvis per half-second)
Real-time antenna and ionosphere calibration every 8 seconds
Map of antenna tile field of view (~30 degrees across) every 8 seconds
Status: 32 tiles on site; currently taking data with 26 tiles
Reionization spatial power spectrum
Bowman, Morales & Hewitt (2006)
MWA power spectrum sensitivity (in principle) at redshift 8
• Focus: Reionization (power spec,CSS,abs)
• Very wide field: 30deg
C.Carilli, A. Datta (NRAO/SOC), J. Aguirre, D. Jacobs (U.Penn)
PAPER: Staged Engineering• Broad band sleeve dipole + flaps
• FPGA-based ‘pocket correlator’ from Berkeley wireless lab, routing via switch
• S/W Imaging, calibration, PS analysis: AIPY, including ionospheric ‘peeling’ calibration, W projection…
100MHz 200MHz
BEE2: 5 FPGAs, 500 Gops/s
150 MHz PWA-4/PGB-8
Powerspectrum
Antenna Development for LUNAR (Bradley NRAO)
Optimize the electromagnetic behavior of the four-element helical array through parametric modeling.
Study effects of lunar deployment tolerances.
Develop a viable mechanical design for the low-mass, folding antenna truss structure.
Build prototypes for operation at 137 MHz and determine beam patterns by measuring the downlink power from a constellation of LEO satellites.
LARC Concept of the Lunar Radio Array
Notional design completed as part of NASA Award NNX08AM30G
The Self-Tending Array Node and Communications Element
-- STANCE --
Quad helical antennas, grounding cavity, and folding support truss adopted as the baseline design.
NRAO Statement of Work: Software requirements
Years 3 + 4: half-time postdoc position will be used to study the software requirements for the lunar array to detection the cosmological HI 21cm singal. Funding for the other-half time is being sought within the NRAO algorithms development group. Goals:
1. Report on telescope software requirement, based on science requirements and design, summarizing processing and analysis software requirements.
2. A report reviewing the current software being written for low frequency ground-based arrays, making recommendations as to aspects of these systems that can be incorporated into the Lunar software design.
3. If time allows, explore low frequency data processing using data from existing low frequency instruments.
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