carma dick plambeck uc berkeley (for the carma consortium)
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CARMA
Dick Plambeck
UC Berkeley
(for the CARMA consortium)
www.mmarray.org
+ UChicago SZA 8 3.5-m antennas
Berkeley-Illinois-Maryland Assn. array 10 6.1-m diameter antennas
Caltech array 6 10.4-m antennas
people
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
project manager: Tony Beasley
antennas
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
CARMA CARMA + SZA
# antennas 15 23
# baselines 105 253
collecting area 773 m2 850 m2
M33
BIMA mosaic of M33
• CO 1-0 115 GHz
• 759 pointing centers
BIMA mosaic of M33
• 148 GMCs detected
• overlie HI filaments (HI image: Deul & van der Hulst
1987)
receiver bands
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
freq (GHz) OVRO BIMA SZA210-270 SIS SIS
85-116 SIS SIS (70-116) MMIC
29-37 HEMT HEMT
22 MMIC
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 diam flat area, + baselines to 2 km
• avoid environmental battles
all such sites are in Inyo National Forest, require Environmental Impact Report
Cedar Flat
Juniper Flat
OVRO
environmental studies done for 2 sites
Juniper Flat – 7900’
Cedar Flat – 7300’
Cedar Flat: 20 min drive to OVRO on paved road, maintained (and plowed)
by Caltrans
Highway 168
simulated antenna
Percentiles
25% < 0.12
50% < 0.16
75% < 0.28
225 GHz
array configurations
• 5 antenna configurations, approx 55 pads
• 2 km max baseline
Cedar FlatE-array
(most compact)
synth beam 4.5" at 230 GHz
Highway 168
D-arraysynth beam 1.8"
C-arraysynth beam 0.8"
B-arraysynth beam 0.32"
A-array synth beam 0.13"
A-array u,v coverage for declination –30 10-m antennas only
(15 baselines)
u,v coverage for declination –30 10-m vs 10-m, 6-m vs 6-m antennas only
(60 baselines)
u,v coverage for declination –30 correlate all antennas
(105 baselines)
A-array synthesized beam, declination –30 0.26 × 0.14" FWHM
5% contours
BIMA detection of
86 GHz radio flare in Orion
• 20 Jan 2003
• beam 0.9 x 0.5''
Bower et al 2003
86 GHz flux increased from 40 mJy to 140 mJy in ~ 4 hrs
20 Jan 2003 02-06 UT
20 Jan 2003 06-10 UT
most compact array
• BIMA antennas within collision range
• SZA provides even shorter spacings
• combine with single dish measurements from 10.4-m antennas
• avoid ‘custom’ vehicle
• 50% of weight on tow vehicle for traction
antenna transporter
transporter tow vehicle: 6-wheel drive military truck (Oshkosh
MTVR)
Current Conceptantenna transporter
fiberoptics
• all communication with antennas via 8 singlemode optical fibers
• length change with temperature is 1 part in 105 – need round trip phase measurement
• based on existing BIMA system
diurnal changes in fiber length (BIMA data from July 2002)
• 135’ of fiber at outdoor air temp ( = 200 nsec)
~ 2 psec/C
~ 180°/C at 230 GHz
Sun hits fibers
fiber lengths
outdoor air temp
BIMA round trip phase measurement
synthlaserTRX
cpl
RXMXR
cpl RX phslck ref
fiber 1
fiber 2
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)
fiber lengths in each cable track each other within fraction of picosecond
3 fibers in one cable
other cables
raw phases on 3c454.3 through sunrise
phases on 3c454.3 through sunrise after correction
Caltech Cobra correlator• based on FPGAs, not
custom correlator chips
• 4 GHz bandwidth• 256 channels, 20 MHz
resolution• 15 baselines
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
Cobra: each board handles 5 baselines, 500 MHz/baseline, 32 chans/baseline
CARMA: reprogram FPGAs to handle 10 baselines, add spectral line capability
graduate student training
John Carlstrom
Leslie Looney
BIMA summer school
public outreach
BIMA antenna move
• build new antenna bases (compatible with pad design, transporter) at high site
• dismantle antennas at Hat Creek, load onto trucks: 2 trucks/antenna
• 1 convoy = 2 trucks; travel time 4-5 days
• entire antenna move approx 8 weeks
moving the BIMA antennas: keep dish and feed legs intact
OVRO antennas will be dismantled to pass through
“the narrows”
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