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● Radio telescope arrays
– 5 - 5000 km diameter
– Resolution arcmin to micro-arcsec at radio wavelengths
● Similar (baseline/ wavelength) for other regimes
– IR - mm e.g. IRAM, ALMA (Gary Fuller)
– Optical e.g. VLTI
Access to Aperture Synthesis Data through the VO
Anita Richards, AVO, JBO, University of Manchester
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M82 - MERLINMuxlow/Pedlar/Wills
EVN
Interferometry - strengths ....● Milli-arcsec resolution
● Sub-mas astrometry, define ICRF
● Multi-scale images from visibility data
● Radio (and some other)
– Non-thermal emission
– (Almost) no extinction
– 10-7 spectral resolution
– Polarization
– Intrinsic wide field of primary beam (MERLIN >104 synthesised beam) 3C264
Lara et al MERLIN+EVN
EVN MERLIN
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Obstacles and Solutions
Visibility data sets >Gb already
Fourier transforms expensive
Most sensitive images lose spatial/time/spectral resolution
Potential field of view ~108 pixels =102 screen dumps
Incomplete apertures - missing angular scales
Requires specialised software, intensive user support
PSR timing, light curves, modelling visibilities etc.
Remote data reduction
Parallel processing
Offer choice of processing routes
Image required region /resolution on demand
Combine multi-array data (&/or upgrade interferometer!)
Pipeline processing, offer simplified user options, &/or remote use of software
Store (reversibly) calibrated visibility data
Many VO Solutions!
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Radio interferometry archives
MERLIN+HST2001
B
1993: Pre-RSN 2001: RSN
ARadio supernova
Colina et al. 2001
Current on-line variety:
● Lists of observed sources
● Calibration source plots
● Experiment information
● Retrospective pipelining to FITS images and data
● On-line on-demand imaging
– from visibility archive
– surveys (image cutout)● Pipelining new data into
archive for user access
● Integration of archives/ major catalogues into CDS Archive
extraction
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Next generation interferometers● e-MERLIN 2005
– Fibres: 30 Gb/s x 6 telescopes [2 PB/day]
– Correlator: 0.5 TB/day● eVLA 2006
● ALMA 2007
● VLTI, e-EVN, SKA etc.
● (e)-EVN incremental
– Disc recording soon
– Data-rate ~e-MERLIN (for starters...)
MERLIN e-MERLIN
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Astronomical technology drivers● Astronomy data sets
– massive
– free (mostly)● Interesting to research/
commerce organisations
– DB providers
– software engineers,
– ontologists
– network providers
● eEVN connections via Géant plausible (DANTE)– local loops going in now
– Real-time demo by 2004
● Fast response to
– variability
– RSNe etc● More data!
● Fibres available to VO?
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European Topology -
UK SuperJANET4
CERNManchester/Jodrell
NL SURFnet
iGrid 2002 JIVE
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Facility-based data centres?● MERLIN archive will
– provide an increasing amount of on-line data
– impliment (processor speed/staffing) limited image server
– upgrade database (very soon)
– continue access via CDS
– become AstroGrid data centre, test/impliment web and grid services (soon)
● e-MERLIN will provide an archive
– open and restricted access as appropriate
– simplified and remote data processing
– all processing reversible, data recycling in many forms● As will ALMA, SKA etc. etc (locations tbd).
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VO-linked data centres ● Interferometry data centre(s) could
– speed up implimentation of current plans e.g.● access to spectral line data/cubes, chemical DBs?● explore exploitation of parallel processing
– become fully VO-compliant● develop standards for interferometry data providers
– mirror or link or otherwise provide interface for ● any interferometry data● on-demand user processing
– integration with other VO data and facilities e.g.● multi-wavelength comparison● authentication● high-resolution image alignment (commonest cases)