Radio telescope arrays

1
Access to Aperture Synthesis Data through the
VOAnita Richards, AVO, JBO, University of
Manchester

• 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

2
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 gt104
  synthesised beam)

EVN MERLIN
3
Obstacles and Solutions

• Visibility data sets gtGb 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!

4
Radio interferometry archives

• 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

MERLINHST 2001
B
A
Radio supernova
2001 RSN
1993 Pre-RSN
Archive extraction
Colina et al. 2001
5
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
6
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?

7
European Topology -
iGrid 2002 JIVE
NL SURFnet
Manchester /Jodrell
CERN
UK SuperJANET4
8
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).

9
VO-linked data centres 3

• 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)