Fwd: Light curves in the IVOA

[Matthew Graham]

Begin forwarded message:

> From: Raul Gutierrez Sanchez <raul at cab.inta-csic.es>
> Date: June 15, 2010 8:18:52 AM PDT
> To: Roy Williams <roy at cacr.caltech.edu>
> Cc: dm at ivoa.net, dal at ivoa.net
> Subject: Re: Light curves in the IVOA
> 
> 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
> 
> -- 
> -----------------------------------------------------------------------------
> 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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