sma submillimeter vlbi status report submillimeter vlbi status report ... eht vlbi, and sma is well...
TRANSCRIPT
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
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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 ?