● 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

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

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!

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

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

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?

European Topology -

UK SuperJANET4

CERNManchester/Jodrell

NL SURFnet

iGrid 2002 JIVE

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).

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)