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