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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 ?
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