Light curves in the IVOA

[Roy Williams]

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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