Server conversion libraries from spectra native format to IVOA SED format


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The problem

The SSA specification allows for "native FITS", which means data centres can deploy an SSA server without changing their FITS files.


"Native FITS" spectra exist in a variety of formats/conventions. Client VO tools need to understand all of these to ensure that they can handle the data returned by SSA responses.

The purpose of this WP7 task is to facilitate VO adoption for Spectra. A small library, to be integrated in the server side by a data centre, should translate "native" fits to IVOA Spectrum Data Model fits format. Hence any clients able to understand this standard fits format can handle spectra stored in a "native" fits format.


The different native FITS conventions for spectra

Ground-based spectroscopy


Stored in the primary HDU, either as a:

  • "1-d" image on primary HDU
    • naxis = 1, naxis1 = n
  • 1-row "2-d" image on primary HDU
    • naxis = 2, naxis1 = n, naxis2 = 1

Where n = number of data points.


Not stored in the file, but instead is calculated as

( i - crpix1 ) * cdelt1 + crval1

Where i = 1..n


No error information is provided


Metadata should follow the FITS serialisation of the IVOA Spectrum Data Model.

Possible points for discussion within the task

  • One of main issues that reduce the number of SSAP implementations in small institutions is the lack of a conversion library from spectra in native format to a IVOA SED compatible one
  • Although native format is allowed in the specification, there is not too much support about how to publish this native data
  • Small library to be integrated in the server part could be used

WP7 objectives fulfilled

  • 5, 6, 7

Possible Internal Deliveries:

  • Conversion package to pre-convert or convert on-the-fly spectra to SED format
  • Integration in DAL service generation Toolkits


Topic attachments
I Attachment History Action Size Date Who Comment
Tartar spectralconverter.tar r1 manage 130.0 K 26 Jul 2010 - 15:31 AlbertoMicol  
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Topic revision: r5 - 26 Jul 2010 - AlbertoMicol
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