(r6) SpectrumDataModelRFC < IVOA

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Spectrum Data Model RFC

This document will act as RFC centre for the Spectrum Data Model 1.01 Proposed Recommendation.

Review period: 16 May 2007 to 12 Jun 2007 (still open)

In order to add a comment to the document, please edit this page and add your comment to the list below in the format used for the example (include your WikiName so authors can contact you for further information). When the author(s) of the document have considered the comment, they will provide a response after the comment.

Discussion about any of the comments or responses should be conducted on the data model mailing list, dm@ivoa.net.

Comments

First sample comment (by BrunoRino): ...
- Response (by authorname): ...

AndreaPreiteMartinez - 19 Jun 2007
- I have revised the UCDs in Tables 1, 2 and 3. The revised tables can be found here. Note that rows with changed UCDs are in bold+italic.
- Pag.23: erase sentence "My solution for brightness... "
- Pag.23 last line: change with "Note: we propose for the next version of the IVOA REC UCD-list to (a) change the flag of pos.eq from S to Q, (b) add two new words em.start, em.end to indicate the lower/start and upper/end boundaries of a spectral interval (as already done for the time axis)"

GaryFuller - 19 Jun 2007
- Does the model allow for double sideband spectra? That is spectra for which each pixel can correspond to two different frequencies or wavelengths? This is a fairly common situation in the mm and submm.
- More generally what about the issue of describing how to convert between two different spectral axes, for example in the dsb case the upper and lower sideband frequency?
- Is there support for non-uniform spectral (and temporal) axes?
- In derived data fields signal-to-noise ratio seems a poorly defined quantity as it depends on what signal, spectral feature, is of interest to a particular user. A value for the rms noise level on the other hand would be very useful but doesn't seem to be in the model.

JonathanMcDowell -20 Jun 2007

Gary:

We discussed the double sideband spectrum case but decided that it complicated the model too much for version 1. We'll revisit this in future, and for now you just have to pick one sideband as the nominal frequency, maybe providing two Spectrum instances, one for each sideband. We acknowledge this is a limitation, as is the inability to represent two different spectra axes in a single instance.

The S/N is a bit vague, but was requested by some data providers for who a single target object is the norm. There is no rms noise, but there is a 'typical (1 sigma) error' in StatError which does much the same thing. We may add rms in a later rev but not this one.

We do, however, support non-uniform axes, since each spectral coordinate is listed explicitly.