Jodrell Bank MERLIN/VLBI National Facility - here, just MERLIN radio interferometer.
2. Current archive status and description: a) How are data stored?
Post-1991: Raw visibility data - DAT tapes and on-line Most continuum data 1993-1999 inclusive - on-line (RAID) calibrated visibity data and images. Data are stored in AIPS; data products e.g. plots, metadata, on disc.
Pre-1991: Mostly DAT tapes but requiring special software, we have no plans at present to provide these data other than manually on-demand.
All further replies refer to post-1991 data.
b) How are data catalogued?
MiniSQL database (soon to be upgraded, probably to MySQL)
c) Do you provide information about sources (as distinct from about
observations) e.g. calibrator lists, target properties, and if so
is this:
i) catalogued information?
Not yet
ii) plots?
Yes
3. What can be accessed on-line?
Lists of observed and processed sources. See 6.; in addition, for processed data, more information e.g. No. visibilities, is available, plus plots of calibration and centre-field images plus FITS image data. More FITS data coming soon.
4. Who can access it?
Open access to lists of public domain sources Fuller searches for information can be made internally at JBO.
5. What are the methods of access?
Web form or via CDS
6. What search parameters are available?
Name (SIMBAD name resolver can be invoked) or RA/Dec; search radius; freq. band; bandwidth; dates.
7. What is your Archive Policy?
See http://www.merlin.ac.uk/archive/archivepolicy.html - usually data are open access after 1 yr.
8. What software do you use?
Local software to create FITS files from raw data. AIPS, perl, cgi
9. What software do users need, and can you provide it?
AIPS - standard NRAO release, MERLIN User Guide (MUG) on-line (or other common packages e.g. Difmap can be used).
10.What format(s) are your data in (or can be translated into)?
Raw data - local format
AIPS FITS files
Archive log catalogue can be obtained as VOTable via CDS
11.Do you use pipelines?
Archive pipeline; also a user-operated pipeline for single experiments (implimented as a runfile or an AIPS procedure)
12.How far are data normally reduced before being supplied to the
user?
Recent data - often raw, sometimes calibrated visibilities. Archive data - calibrated visibilities, rough images of centre of field.
13.Are these stages:
a) documented?
Sample annotated script for archive data processing is online, plus
MUG describes (in too much detail!)
AIPS history files (not entirely complete nor reliable in practice)
b) reversible?
Initial flux scale/bandpass is applied before data are turned into FITS but this can be altered in AIPS. All further calibration and editing of visibility data is stored in extension tables which can be removed. These data are used to produce images etc. (including lightweight selected calibrated visibility data) - the final products are not in general 'reversible' but can be extracted on-demand from the calibrated visibilities.
14.Can data be processed remotely?
Prototype web interface can produce images of desired size and resolution; more coming soon.
15.What Virtual Observatory projects (if any) are you involved in?
AstroGrid, AVO, IVOA
16.Do you use explicitly any interoperability tools, e.g. data models,
UCDs, VOTable?
Archive catalogue is described with UCDs. Further tools under development through this initiative e.g. data model and through VO initiative e.g. publishing archive as web wervice. VOTable retrievable from Vizier.
17.Do you publish any data via existing VO-like facilities e.g. CDS,
MAST? Part of archive catalogue is available through Vizier and images can also be viewed in Aladin.
18.Making data acess easier for a wider range of astronomers - what are
your views on whether/how these suggestions should be implimented: a) Using a VO interface to radio observatories/data centres to run
hidden software to provide required image, light curve, visibilities etc.?
Yes
b) Supplying information about hidden processing (software, versions,
parameterisation, etc)?
Yes but a lot of effort is needed to select and explain information useful to non-specialists
c) Standardising the software in use at radio observatories/ data
centres?
Yes
d) Standardising the format of data products?
Yes
19.What do you think astronomers want from your data?
20.What are your plans for archive development or any other relevant
suggestions?
Impliment public on-line on-demand access to images at any position in the field of view and other data products.
Become a fully grid-enabled data centre in AstroGrid.
Supply all public data via CDS insomuch as it can be handled by Vizier/Aladin.
Apply the cut-out server developed around Aladin for the AVO demo to key project data involving very large fields (~10^4 pixels to a side).
We have yet to develop pipelines for full spectral data reduction ie producing image cubes, although visibilities can be calibrated. We also have to improve automatic editing and processing conditional on data quality, especially important at the highest and lowest frequencies.
VO access will be designed into the e-MERLIN archive.