CARMA

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CARMA

• Dick Plambeck
• UC Berkeley
• (for the CARMA consortium)
• www.mmarray.org
• URSI, 24 June 2003, Columbus, Ohio

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Berkeley-Illinois-Maryland Assn. array 10 6.1-m
diameter antennas
Caltech array 6 10.4-m
antennas
UChicago SZA 8 3.5-m antennas
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people
project manager Tony Beasley

• OVRO
• D. Woody
• S. Scott
• J. Lamb
• D. Hawkins
• J. Carpenter
• A. Sargent
• G. Blake
• N. Scoville

• Berkeley
• D. Plambeck
• M. Wright
• A. Bolatto
• C. Kraybill
• M. Fleming
• L. Blitz
• W.J. Welch

• Maryland
• M. Pound
• P. Teuben
• K. Rauch
• S. Vogel
• L. Mundy
• A. Harris

• Illinois
• R. Plante
• D. Mehringer
• L. Snyder
• R. Crutcher
• L. Looney

programmers, engineers, technicians, postdocs,
graduate students
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antennas
CARMA CARMA SZA
antennas 15 23
baselines 105 253
collecting area 773 m2 850 m2

• 3 different antenna diameters - a heterogeneous
  array
• exploit new algorithms for mosaicing, high
  fidelity imaging
• sensitive to wide range of spatial frequencies
  image large objects

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M33
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BIMA mosaic of M33

• CO 1-0 115 GHz
• 759 pointing centers

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BIMA mosaic of M33(Engargiola et al. 2003)

• 148 GMCs detected
• overlie HI filaments (HI image Deul van der
  Hulst 1987)

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receivers
freq (GHz) OVRO BIMA SZA
210-270 SIS SIS
85-116 SIS SIS (70-116) MMIC
29-37 HEMT HEMT
22 MMIC

• for the 1mm and 3mm bands
• 4 GHz bandwidth, 1 polarization at first light
• continuum sensitivity 2-3 mJy/beam, in 1 minute
• 230 GHz brightness sensitivity 1 K for 1 km/sec
  channel, 1'' beam, in 1 hour

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site selection and acquisition

• requirements
• within 60 minute drive of existing OVRO
  infrastructure
• elevation 7000-9000 ft for good atmospheric
  transmission but low snow load
• 400-m diameter flat area, baselines to 2 km
• avoid environmental battles

all such sites are in Inyo National Forest,
require Environmental Impact Report
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environmental studies done for 2 sites
Cedar Flat
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Juniper Flat 7900
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Cedar Flat 7300
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Cedar Flat 20 min drive to OVRO on paved road,
maintained (and plowed) by Caltrans
simulated antenna
Highway 168
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225 GHz
? Percentiles 25 lt 0.12 50 lt 0.16 75 lt 0.28
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BIMA antenna move

• keep dish and feed legs in one piece
• move 9 antennas in 8 weeks

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OVRO antennas will be dismantled to pass through
the narrows
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array configurations

• 5 antenna configurations, approx 55 pads
• 2 km max baseline

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Cedar FlatE-array(most compact)synth beam
4.5" at 230 GHz
array center
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E-array

• BIMA antennas within collision range
• SZA provides even shorter spacings
• combine with single dish measurements from 10.4-m
  antennas to recover all spatial frequencies

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A-array 0.13" synth beam
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u,v coverage for declination 30 4-hr
observing track
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A-array synthesized beam, declination 30 0.26
0.14" FWHM
5 contours
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BIMA A-array detection of a stellar flare in
Orion (
86 GHz, synthesized beam 0.9 0.5" )
20 Jan 2003 4 UT
20 Jan 2003 8 UT
30 mJy
150 mJy
BN
IRc2
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antenna transporter

• use common transporter for 6-m and 10-m antennas
• avoid custom vehicle
• 50 of weight on tow vehicle for traction

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transporter tow vehicle 6-wheel drive military
truck (Oshkosh MTVR)
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fiberoptics

• all communication with antennas via 8 singlemode
  optical fibers
• use standard SMF 28 fiber - length change with
  temperature is 1 part in 105
• use BIMA round trip phase measuring system to
  monitor fiber lengths

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diurnal changes in fiber length (BIMA data from
July 2002)
Sun hits fibers
fiber lengths

• 135 of fiber at outdoor air temp (?
  200 nsec)
• ?? 2 psec/C
• ?? 180/C at 230 GHz

outdoor air temp
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BIMA round trip phase measurement
advantage no electronics at the antenna, just a
fiber coupler disadvantage lengths of fibers 1
and 2 must track with temperature and flexure
(requires loose tube fiber)
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raw phases on 3c454.3 through sunrise
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phases on 3c454.3 through sunrise after correction
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• Caltech COBRA correlator
• based on FPGAs, not custom correlator chips
• 4 GHz bandwidth
• 256 channels, 20 MHz resolution
• 15 baselines

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CARMA first light correlator

• uses COBRA hardware design
• 15 telescopes, 105 baselines
• 8 independent sections
• may be positioned anywhere in 4 GHz IF band
• choose 2, 8, 31, 62, 125, 250, or 500 MHz
  bandwidth
• velocity resolution 0.04 to 40 km s-1/ channel at
  1.3 mm

separate SZA correlator
8 antennas, 28 baselines, 8
GHz bandwidth
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COBRA each board handles 5 baselines, 500
MHz/baseline, 32 chans/baselineCARMA reprogram
FPGAs to handle 10 baselines, add spectral
line capability
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timeline
Jan 2003 draft environmental document submitted
Mar 2003 Forest Service decision Cedar Flat
Jun 2003 end of public comment period
Aug 2003 Forest Service record of decision
Oct 2003 appeals period ends
early 2004 SZA operational at high site
mid 2004 move OVRO and BIMA antennas to high site
2005 begin operation
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BIMA summer school
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Alberto Bolatto testing prototype WVR in Berkeley
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Leslie Looney pulling underground fiber for long
baselines
John Carlstrom repairing the Air Products
refrigerator on receiver 3
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7th graders at Hat Creek