Light curves in the IVOA

[Raul Gutierrez Sanchez]

Just to mention... There is already a protocol aproved by IVOA (SSAP) 
able to cover the access to TimeSeries data. In fact, the Spanish 
Virtual Observatory has two services of light curves based on this 
protocol, namely:

* OMC (http://sdc.cab.inta-csic.es/omc/jsp/ssap.jsp?pos=0,0&size=10),
registered since 2006

* COROT (http://sdc/corotfa/jsp/ssap.jsp?pos=290.557,1.70154&size=0.01),
registered since 2009.

The number of SSAP accesses to the CoRoT archive in the last year 
(>11000) demonstrated that this is a working approach. We propose, 
therefore, to use SSAP (and improve if necessary) as a protocol to 
access light curves.

Data modelling is a more problematic issue still in a earlier 
development stage. Whatever representation is adopted, data models 
should be able to tackle the different representations a light curve may 
have:

X-axis: time, phase,...

Y-axis: intensity (counts, magnitudes, fluxes,...), differential 
intensity (target-standard),...


Best regards,
Raul Gutierrez


Roy Williams wrote:
> 
> To the DM and DAL groups:
> 
> With the increasing importance of synoptic surveys in modern astronomy, 
> I am thinking that the IVOA could expand its repertoire of data objects 
> to include Light Curves. An interoperable protocol for exchanging light
> curves would open the current tight connection between data and 
> classifiers, allowing different light curves to be federated, and data 
> mining codes run on data from different repositories. I propose that the 
> IVOA work towards a Simple Light Curve Access Protocol (SLiCAP).
> 
> There would be two parts to the standard, as we have with SCS, SIAP, 
> SSAP etc:
> -- How to represent a light curve as a file (Data Modeling)
> -- How to query a light curve repository (Data Access)
> 
> For the standard format, one candidate is the well-documented proposal 
> called simpleTimeSeries [1], which already has strictly defined Time, 
> and good representation of errors, bandpass, and null-detections. There 
> is also the comprehensive architectural proposal from Tody et al [2] 
> which can represent light curves and spectra in a unified way. Another 
> way to represent light curves could be derived from "Referencing STC in 
> VOTable" from Demleitner et al [3].
> 
> For the query service, we might follow what the IVOA has already done 
> with images in the SIA protocol [4]: the request is a cone (RA, Dec, 
> size) and maybe other query paramters, then the response is a table of
> possible matches, with each row having a link to the actual light curve. 
> Other elements of the query protocol might be from the Simple Time-range 
> Access Protocol [5] which essentially extends the cone-search idea to 
> include time. The only difference from SIA would be that there is a 
> light curve under the link rather than an image.
> 
> We have been discussing light-curve representation withing the VOEvent 
> WG for some time, but perhaps it would be good to open the discussion to 
> DM and DAL. I would appreciate any thoughts, comments, or relevant 
> existing work.
> 
> Roy Williams
> 
> 
> [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://www.ivoa.net/Documents/SIA/
> [5] http://wiki.astrogrid.org/bin/view/Astrogrid/SimpleTimeAccessProtocol
> 

-- 
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Raúl Gutiérrez Sánchez      ( raul at cab.inta-csic.es )
Lab. de Astrofísica Espacial (www.laeff.cab.inta-csic.es)
European Space Astronomy Centre (ESAC)
Villafranca del Castillo - E-28691 Villanueva de la Cañada - Madrid - Spain
Tel.: 34 91 8131260    Fax.: 34 91 8131160
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