Utypes for Light Curves?

[Roy Williams]

> Have a look at Bruno's
> http://www.ivoa.net/internal/IVOA/InterOpNov2009DM/sample.html

Alberto
This looks like an interesting document. Finally the Utypes are brought 
out into daylight where we can see them. As I have written before, I am 
interested in building a way for Light Curves to be serialized, and 
building an access protocol for fetching LC from a repository. There are 
several suggestions for how to represent LC ([1] thru [4] below), some 
from within the IVOA community, some not. I am guessing that the Utypes 
from the above is a way to elaborate the generalities of the DAL2Arch in 
ref [2], is that right?

Following this, the Time Axis data model and Flux Axis data models look 
quite relevant. I am imagining a representation of a Light Curve that 
has some parameters and a table wrapped in a VOTable. The parameters and 
fields will include these things from the above, for example
<FIELD utype="FluxAxis.Accuracy.StatError"/>  for error in flux
<FIELD utype="TimeAxis.Coverage.Location.Value"/> for time of observation

Is that correct? If so we need a few more Utypes:
-- The FluxAxis data model does not seem to have an actual measured 
value of Flux. What the Utype for the FIELD that has the flux value?
-- How do we represent the filter used for the observations? Don't we 
need upper and lower limits for the filter, central wavelength, name of 
the filter, that sort of thing? The Spectral DM lookslike it has some 
useful Utypes, but a Spectrum is not the same a Filter.
-- How does the TimeAxis model work with STC? It says "Midpoint of 
exposure on MJD scale". What time scale is this, where is the observer, 
is it barycentric, etc etc. How does this sort of thing integrate with 
the Utypes? Can [2] and [3] work together in this? Or maybe [2] and [4]?

Thank you
Roy


[1] http://www.dotastro.org/simpletimeseries/
[2] http://www.ivoa.net/Documents/Notes/DAL2Arch/
[3] http://vo.ari.uni-heidelberg.de/docs/note_stc_20100420.pdf
[4] 
http://hea-www.harvard.edu/~arots/nvometa/STC/STCTimeSeriesTableFormat.pdf




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