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AMI: Telescope description and capabilities
Keith Grainge

AMI Day -- 30 September 2011


A R C M I N U T E M I C R O K E LV I N I M AG E R ­ A M I
· Telescope designed for SZ ... but other science areas · Sited at Lords Bridge · = 15 GHz; = 6 GHz · Two interferometric arrays · AMI Small Array -- Ten 3.7m dishes -- 5 ­ 18 m baselines · AMI Large Array -- Upgraded Ryle Telescope -- Eight 12.8m dishes Ten times SA area -- 18 ­ 110 m baselines

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W H Y T W O A R R AY S ?

· Background radio sources are dominant contaminant.

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A M I T E C H N I C A L S U M M A RY
SA LA 3.7 m 12.8 m 10 8 45 28 5­20 m 18­110 m 19.6 5.6 3 30 30 mJy s-1/2 3 mJy s-1/2 13.5­18.0 GHz 4.5 GHz 6 0.75 GHz I+Q

Antenna diameter Number of antennas Number of baselines Baseline length 16-GHz power primar y beam FWHM Synthesized beam FWHM Flux-density sensitivity Observing frequency Bandwidth Number of channels Channel bandwidth Polarization measured

· Channels 1 and 2 not used because of correlator and RFI · Typically restrict obser ving to above dec 20

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S I G N A L PAT H
· · · · RF = 12 - 18 GHz downconver ted to IF = 6 - 12 GHz. 24 GHz LO generated from 12 GHz ­ notch filters required. Two levels of phase switching (individual Walsh function for each antenna) Strip-line band-pass equilisation modules.

· 10 bit path compensation (12 for Large Array). -- Stripline; semi-rigid; coax. · Loss and slope in long length balanced by echosorb over strip line in shor t length. · Automatic Gain Control (AGC) loop just before correlator · System temperature monitor system · Analogue lag correlator

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S N A P - S H OT U V- C OV E R AG E

Large Array

Small Array

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O T H E R T Y P I C A L O B S E RV I N G M O D E S

· Cluster field: pointed SA and 61+19 mosaic -- 200 µJy noise on SA -- 125 µJy noise (centre) on LA · Sur vey fields: hexagonal close packed mosaics -- 60 µJy source confusion limit on SA · Obser ving below dec 20 possible but time consuming Mosaic observation of CORNISH Survey 300 µJy noise

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SA DRIFT SCAN

· · · · · · ·

Par t of the AMI SA galactic drift scan Approximately 6 hours of data Magenta circles: detected sources with NVSS counterpar ts. Blue contours: IRAS 23507+6230 not identified by NVSS Also supernova remnant G116.9+00.1 Noise level 2 mJy; 3 arcmin resolution All sky between dec 20 and 70 would take 7 months observing

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LA DRIFT SCAN
· Approximately 18 minutes of data · 9 sources detected; fluxes and positions consistent with 10C · 500 µJy noise; 30 arcsec resolution · All sky between dec 20 and 70 would take 21 months observing · Anti-siderial driving speed up (noise penalty)

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O B S E RV I N G E FFI C I E N C Y
· 24 hours a day; 365 days a year ; no real-time telescope operator · Telescope on sky for 90% of time · 25% of time "lost" to weather

O P E R AT I O N S C O S T S
· AP Group / Physics depar tment has been subsidising AMI operations · Annual costs: Staff (0.8 PDRA; 0.15 PI; 2 technicians) -- 174k Consumables; repairs; refurbishment -- 59k Electricity -- 35k · Total -- 268k

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P O S S I B L E U P G R A D E PAT H : D I G I TA L C O R R E L ATO R
· Improved rejection of systematics -- Currently abandon cluster fields with radio source brighter than 10 mJy · Improved RFI rejection Low declination obser ving Increased bandwidth; improved frequency lever-arm · Possible new science areas available

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P O S S I B L E RO AC H A R C H I T E C T U R E F O R L A

· · · ·

4 bit 10 GSA/s ADCs ( = 5GHz) Total cost (digital) 60k$ Total power 1kW Analogue components: possible reuse of old VSA mixers etc

· Other possibilities: -- 6 GSA/s ADCs already tested at CASPER; double sideband system; ROACH-II boards; 16k spectrometer possible -- Uniboard (essentially 8 ROACH boards on 1 board)
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A M I T E C H N I C A L S U M M A RY
SA LA 3.7 m 12.8 m 10 8 45 28 5­20 m 18­110 m 19.6 5.6 3 30 30 mJy s-1/2 3 mJy s-1/2 13.5­18.0 GHz 4.5 GHz 6 0.75 GHz I+Q

Antenna diameter Number of antennas Number of baselines Baseline length 16-GHz power primar y beam FWHM Synthesized beam FWHM Flux-density sensitivity Observing frequency Bandwidth Number of channels Channel bandwidth Polarization measured

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