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<p>Hi,</p>
<p>This email sent yesterday to the three lists was apparently not
sent to voevent. (Time domain maling list). I was apaprently not
registered there.</p>
<p>For those on several lists, sorry for the SPAM<br>
</p>
<p>Cheers</p>
<p>François<br>
</p>
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<th valign="BASELINE" align="RIGHT" nowrap="nowrap">Sujet :
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<td>TimeSeries of position (Asteroid)</td>
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<th valign="BASELINE" align="RIGHT" nowrap="nowrap">Date : </th>
<td>Thu, 22 Nov 2018 21:51:19 +0100</td>
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<th valign="BASELINE" align="RIGHT" nowrap="nowrap">De : </th>
<td>François Bonnarel
<a class="moz-txt-link-rfc2396E" href="mailto:francois.bonnarel@astro.unistra.fr"><francois.bonnarel@astro.unistra.fr></a></td>
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<th valign="BASELINE" align="RIGHT" nowrap="nowrap">Pour : </th>
<td><a class="moz-txt-link-abbreviated" href="mailto:dm@ivoa.net">dm@ivoa.net</a> <a class="moz-txt-link-rfc2396E" href="mailto:dm@ivoa.net"><dm@ivoa.net></a>, <a class="moz-txt-link-rfc2396E" href="mailto:dal@ivoa.net"><dal@ivoa.net></a>
<a class="moz-txt-link-rfc2396E" href="mailto:dal@ivoa.net"><dal@ivoa.net></a>, <a class="moz-txt-link-abbreviated" href="mailto:voevent@ivoa.net">voevent@ivoa.net</a></td>
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<pre>Der Dave, all,*
Before interop Dave asked me to provide how a TimeSeries of Asteroid
could look like with the current ts model proposal and Utypes serialisation.
<blockquote type="cite"><pre>Someone recently described to me a use case that I haven't seen in our
discussions.
To help me understand how to use the new model, could you send me a
simple example of how a time series of position over time would look ?
For a single moving object we would get multiple ra/dec or Point
values plotted against time.
For a mode complex example, multiple position and magnitude values
plotted against time.</pre>
</blockquote>
You can find a "dummy example" of this at this URL :
<a class="moz-txt-link-freetext" href="http://volute.g-vo.org/svn/trunk/projects/time-domain/time-series/note/DATA/Proposed_Serializations/UTYPES/AsteroidSimple.xml" moz-do-not-send="true">http://volute.g-vo.org/svn/trunk/projects/time-domain/time-series/note/DATA/Proposed_Serializations/UTYPES/AsteroidSimple.xml</a>
Could be from gaia for an Asteroid.
Then Dave gave more details for the second more complex example
<blockquote type="cite"><pre>Two use cases from the Gaia meeting.
Exoplanets, the star will change both brightness and position by tiny
amounts linked to the planet's orbit. Very small and slow changes in
both position and brightness, hard to detect above the noise.
Near earth asteroid will be travelling very fast, and change
brightness in response to distance from the sun, position relative to
the sun, and rotation and shape of the asteroid itself. Very large and
rapid changes in both position and brightness.
Both are valid cases for time series of positions and magnitudes. </pre></blockquote>
This is an attempt for a Near Earth Asteroid
<a class="moz-txt-link-freetext" href="http://volute.g-vo.org/svn/trunk/projects/time-domain/time-series/note/DATA/Proposed_Serializations/UTYPES/AsteroidFull.xml" moz-do-not-send="true">http://volute.g-vo.org/svn/trunk/projects/time-domain/time-series/note/DATA/Proposed_Serializations/UTYPES/AsteroidFull.xml</a>
Data are dummy of course. but with about 1 magnitude amplitude and 1deg position change in 10 days !!!
<i><b>Changes for the Exoplanets use case can be easilly done :</b></i>
There will be no real "look and feel" change for the magnitudes.
For position, the best is probably to set the mid position of the star in the refPOsition of COOSYS (see note below) and to have the lon and lat columns giving the deviation from this
position along the ra and dec axes (and no more ecliptic longitude and latitude). The unit for these two columns will probbaly be "mas" instead of "deg".
Cheers
François
COOSYS note : currently there is no "refPosition" attribute in COOSYS. We propose to add one , taking the opportunity of the change in VOTable schema required to introduce TIMESYS.
this attribute allows accurate distinctions of positions computed from BARYCENTER, TOPOCENTER, GEOCENTER, as well as definitions of standalone "local" spatial frames to code for
very accurate measurements.
</pre>
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