Jonathan Weintroub

SMA Submillimeter VLBI Status Report

Event Horizon Telescope Workshop25 January 2010

SMA

SM

IT

HS

ON

IAN

ASTROPHYSICAL

O

BSE

RV

AT

OR

Y

A

CA

DEMIA SINICA

IA

A

• Stability requirements are most stringent in respect of the sky LO, at around 230 GHz or 345 GHz, a few parts in 1014 needed on 10 s time scales---P2 is quite good

• Absolute time at stations controlled by locking a maser locked 1pps to GPS. Residual error delay removed by post correlation fringe search.

• Keeping supplied with H has been a saga

• Evaluating the possibility of upgrading to Cryogenic Sapphire Oscillator (CSO, not to be confused with CSO)

2

P2 Maser time standard

Allan Deviation P2 & P8 vs. P13

•P2 maser now at SMA on Mauna Kea•P8 maser at SMTO on Mount Graham

3

4

Lab Tests of SMA YIG Systems

About 4 % coherence loss due to phase noise.

5

SMA readiness for 1.3 and 0.85 mm VLBI

• SMA equipped with two Mark5B+ units; 4 Gbps sustained

• At both 1.3 mm and 850 micron, SMA has 2 GHz bandwidth per sideband, supporting 8 Gbps sustained VLBI data rate

• At 1.3 mm, bandwidth doubling units (4 GHz) and wideband receivers support 16 Gbps “burst mode”

• Dual polarization has historically only been a goal for 850 micron. Recently SMA has been investigating 10 GHz BW upgrade, with dual pol on both 1.3 mm and 850 micron

• Fiber connections to CSO and JCMT, support phased array operations with those facilities. However supported wavelengths, bandwidths, polarizations, do vary

• SMA has 1/4-wave plates for both wavelengths

6

Weather trends, and testing plans

• Experience at SMA shows that by far the bulk of time is spent on 230 GHz and 345 GHz operations (1.3 mm and 850 micron).

• Weather and demand supports a roughly 50/50 split.

• Time spend on 690 GHz is negligible by comparison (& so far SMA 400 GHz receivers have poor noise performance)

• Mauna Kea is an excellent site at the wavelengths of interest in EHT VLBI, and SMA is well matched to the program

• One night a week available for engineering testing, generally able to obtain time for VLBI work. Daytime engineering testing ok, observing can be problematic

CSO10 m single dish

(79 m2)

JCMT15 m single dish

(177 m2)

SMAeight 6 m dishes

(compact configuration)(226 m2)

7

Phased Arrays:Submillimeter Valley, Mauna Kea, Hawaii

(aggregate area 482 m2

equivalent of 25 m aperture)

VLBI Phased Array Processor for SMAfielded April 2009, talk here, tomorrow

System deployment and testiBOB delay

compensation

BEE2 calibrationcorrelator

Mark5B+ # 1

Mark5B+ # 2

Linux control computer

Analog phase compensation

UPS power conditioning

Analog Pre-Processors

Jan 2009

!"#$%&$'&()'*+,-'.$/+0$'0$%*(-1')2$'-$3)'#(-$'(-')2(&'$4%(#5'67%82$*'%0$'&)0+-1'/0(-1$&'.$),$$-')2$'96:;6'9<'%-)$--%'%-*')2$'=2%&$*'%00%>'=0+8$&&+0'????@'

A;(B$'C()D&E';FCGH%>&)%8BE'I'6=0(#'JKKLM'

Supplementary material

Station Location A (m2) λ(mm) Bandwidth(GHz)

dual pol? maser?

SMA Mauna Kea 226 1.3 ; 0.8 2 0.8 only YJCMT Mauna Kea 177 1.3 ; 0.8 3 0.8 only (Y)CSO Mauna Kea 79 1.3 ; 0.8 1.8 ? (Y)

‘Hawaii’ Mauna Kea 482 1.3 ; 0.8 1.8 0.8 only YCARMA Cedar Flat, CA 85 1.3 4 N YCARMA-8 Cedar Flat, CA ? 1.3 4 N YSMTO Mt. Graham

Arizona 79 1.3 ; 0.8 4 1.3 & 0.8 YLMT Volcán Sierra Negra

Puebla, Mexico 804 1.3 8 1.3 only NASTE Atacama, Chile 79 0.8 2 N NAPEX Atacama, Chile 113 1.3 ; 0.8 4 1.3 & 0.8 N

ALMA-10 Atacama, Chile 1131 1.3 ; 0.8 4/5.5 1.3 & 0.8 NIRAM PdBI Plateau de Bure,

France 1060 1.3 ; 0.8 4 0.8 only ?IRAM 30m Pico Veleta

Spain 707 1.3 1 1.3 & 0.8 ?