State of Art and Future Trends of Drilling Fluid an Experimental Study
mmVLBI in the Future: technical/experimental
description
Transcript of mmVLBI in the Future: technical/experimental
mmVLBI in the Future:technical/experimental
Shep Doeleman
Haystack Observatory
In Defense of Theory
Do I contradict myself? Very well then I contradict myself, (I am large, I contain multitudes.) --Walt Whitman, "Song of Myself"
High Frequency VLBI Challenges
• Sensitivity: limited by atmospheric coherence, telescope apertures, bandwidth, weather (opacity and coherence).– Past observations limited to brightest
sources.• Baseline coverage: limited by relatively small
number of high demand sub/mm telescopes.• LO quality: phase noise in electronics
increases – loss of fringe amplitude.– First VLBI at new mm sites requires effort.
Challenges cont’d• Scheduling: mm/submm telescopes difficult to
schedule.• Array phasing: all antennas must be phased
prior to summing (you only get one chance).• Hydrogen masers: if atmosphere is good, maser
should not limit coherence time.• Amplitude calibration is difficult: array
phasing, pointing, atmosphere, gain curves.• BBCs have limited Bandwidth• Major improvements can be expected in some
of these areas.
Sensitivity: a solution.
• Old conventional wisdom: collecting area.
• New technical developments – new wisdom– 1983 VLBI BW: 224Mb/s, – 2004 VLBA BW: 512Mb/s.– New disk based VLBI recording systems will
allow multi Gb/s data rates
Mark 5A VLBI Data System
Mk5 cost ~ $15K700 GB disks expected ~2005 – 24 hours @ 1 Gbps unattended(comparable to ~19 VLBA tapes)
Sensitivity: a solution.
• Old conventional wisdom: collecting area.• New technical developments – new wisdom
– 1983 VLBI BW: 224Mb/s, – 2004 VLBA BW: 512Mb/s.– New disk based VLBI recording systems will
allow multi Gb/s data rates.– Leverages COTS technology and industry
demand for affordable, high capacity, high speed hard disks.
– Units can be used in parallel for N Gb/s.
Tape vs. Disc Price Comparison
mmVLBI at Haystack
• 2001-present: focus on 1-2mm VLBI
• 2002: Carried out successful 129, 147GHZ VLBI on Pico Veleta, KittPeak12m, SMTO triangle: – High resolution: Pico-SMTO fringes – 49as– SiO Masers– Collaborators: MPIfR, IRAM, Onsala,
Metsahovi, Arizona Radio Observatory
mmVLBI In the News
v=1 J=3-2 SiO Masers in VY CMa
30 AU
• First 129GHz VLBI image using all phase and amp information.
•Relative astrometry small fraction of beam.
mmVLBI at Haystack• 2001-present: focus on 1-2mm VLBI• 2002: Carried out successful 129, 147GHZ VLBI
on Pico Veleta, KittPeak12m, SMTO triangle: – High resolution: Pico-SMTO fringes – 49as
– SiO Masers
• 2003: Carried out 129, 230GHz VLBI using Pico, KittPeak, SMTO, Plateau de Bure– Detected Pico-SMTO 1.3mm fringes – 34as on 3C279
– World Record: equivalent to 5 RSCH of SgrA* MBH
– Used new generation of VLBI recorders.
• Very promising, but future depends on funding.
Evolution of 3mm Capability
Antenna SEFD
(Jy)
VLBA 5170
PicoVeleta 1700
P. de Bure 1700
Onsala 4000
Effelsberg 2000
Present: 256Mb/s
Antenna SEFD
(Jy)
GBT 500
Apex (Chile) 5000
CARMA 1700
LMT 350
Nobeyama 3000
3-5 years: 1Gb/s
Antenna SEFD
(Jy)
ALMA 60
5-10yrs: 10Gb/s
VLBA-VLBA = 0.8JyPicoV-PdeB = 0.25JyPicoV-PdeB = 0.13Jy*PicoV-VLBA = 0.5Jy
VLBA-VLBA = 0.4JyGBT-LMT = 0.032JyGBT-LMT = 0.016Jy*LMT-VLBA = 0.1Jy
VLBA-VLBA = 0.13JyALMA-LMT = 0.004JyALMA-VLBA = 0.014Jy
Resolution (8000km)=90asTcoh = 20 seconds
Higher recording rates.
Evolution of 1mm Capability
Antenna SEFD
(Jy)
KittPeak 22000
PicoVeleta 2500
P. de Bure 2500
SMT 15000
Present: 0.5Gb/s
Antenna SEFD
(Jy)
JCMT 7800
APEX-Chile 5500
CARMA 2500
LMT 500
SMA 2500
CSO 15000
3-5 years: 4Gb/s
Antenna SEFD
(Jy)
ALMA 100
5-10yrs: 10Gb/s
PicoV-PdeB = 0.4JyPicoV-KittPeak = 1.15Jy LMT-CARMA = 0.06Jy
LMT-SMT= 0.15Jy
ALMA-LMT = 0.008JyALMA-SMT = 0.042Jy
Resolution (8000km)=34asTcoh = 10 seconds
UltraVLBI Proposal• Submitted to ATI program at NSF• Outfit largest cm antennas (Effelsberg, Arecibo,
GBT, WSRT, Jodrell bank) with 4Gb/s recording systems: <1Jy/beam rms.
• Outfit best mm sites with 4Gb/s systems: JCMT, SMTO (CARMA, LMT, SMA, ALMA, APEX)
• Target science requiring sensitivity: SNR in Galactic mergers, GRBs, Grav. Lenses, Stellar VLBI, SgrA*!!
• Waiting to hear …
230GHz VLBI Observations
Proposed VLBIon JCMT-HHTbaseline.
Just a detection willprovide a firm uppersize limit.
Next Generation VLBI System• Multiple Digital BBC units (500MHz each).
– Cost: 20K each.
• Multiple MK5b units (1Gb/s each).– Cost: 16K each.
• H-maser with y(10sec)<=3e-14.– Cost: 175K.
• Rack with power supplies, backplane, GPS clock, – Cost: 20K
• Total: $270K/new station, much less if maser is already available.
Summary• Over next decade: BW x40, Element area x25, means
capable 230GHz imaging arrays.• Phase stability of mm/submm arrays is very important:
CARMA, ALMA, PdeBure.• Creating low phase noise LO systems for submm
VLBI is necessary.• VLBI arrays up to 345 and 450GHz are possible.• ‘Widebanding’ IFs and receivers will be a
requirement.• Scheduling: need turn-key operation from single dish
to VLBI.• Current proposed work: 4Gb/s VLBI on SgrA* in 3
years.
END