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<div class="moz-cite-prefix">Dear Alberto,</div>
<div class="moz-cite-prefix"><br>
</div>
<div class="moz-cite-prefix"> For sure it's possible to have the
parameters of Greisen et al in an extension.</div>
<div class="moz-cite-prefix"> But I'm still wondering how useful
and handy it is.</div>
<div class="moz-cite-prefix"><br>
</div>
<div class="moz-cite-prefix"> Again, definitely I see the
interest of delivering these metadata (which are actually fitw wcs
metadata) at the SODA level in order to create a velocity cutout
query.</div>
<div class="moz-cite-prefix"><br>
</div>
<div class="moz-cite-prefix"> But I'm still filling chilly for
data discovery.</div>
<div class="moz-cite-prefix"> Let's look at a couple of
examples</div>
<div class="moz-cite-prefix"><br>
</div>
<div class="moz-cite-prefix"> select * from
obscore-with-vel-extension where dataproduct_type= cube and v_min
= 800 and v_max= 1200 and em_unit = km/s and em_ucd = vel <br>
</div>
<div class="moz-cite-prefix"><br>
</div>
<div class="moz-cite-prefix"> then you get for example <br>
</div>
<div class="moz-cite-prefix"> optical cubes with h
alpha line redshifted by ~1.7 to ~2.6 nm</div>
<div class="moz-cite-prefix"> and radio cubes with
21 cm line redshifted by ~0.55 to ~0.8 mm</div>
<div class="moz-cite-prefix"> and probably many
others</div>
<div class="moz-cite-prefix"><br>
</div>
<div class="moz-cite-prefix"> So, will you say, we have to
give the reference line to get h alpha redshifted line ONLY <br>
</div>
<div class="moz-cite-prefix"> <br>
</div>
<div class="moz-cite-prefix"> select * from
obscore-with-vel-extension where dataproduct_type= cube and v_min
= 800 and v_max= 1200 and em_unit = km/s and em_ucd = vel and
em_ref = 656.3 10**-9 <br>
</div>
<div class="moz-cite-prefix"><br>
</div>
<div class="moz-cite-prefix"> But then what you get is
something which may contain the redshifted halpha line but maybe
also nothing about halpha (because the velocity axis is not a
guarantee for redshifted line to be there in the dataset) but
instead the NII line at 658.4.</div>
<div class="moz-cite-prefix"><br>
</div>
<div class="moz-cite-prefix"> Or even worse = (highly)
redshifhted halpha and (nearly) non redshifted NII !!! (and there
we are close to the 4D use case)<br>
</div>
<div class="moz-cite-prefix"><br>
</div>
<div class="moz-cite-prefix"> So I find this misleading and I
think we can find also the same kind of mess in the radio domain
(imagine very high z pushing 21 cm in low frequency radio or mm
lines in the metric domain for example )</div>
<div class="moz-cite-prefix"><br>
</div>
<div class="moz-cite-prefix"> So if you want velocity cubes in
the halpha redshift rang eas above just query</div>
<div class="moz-cite-prefix"> select * from
obscore-with-vel-extension where dataproduct_type= cube and em_min
= 658.0 10**-9 and em_max = 658.9 10**-9 and em_unit = km/s and
em_ucd = vel and em_ref = 656.3 10**-9<br>
</div>
<div class="moz-cite-prefix"><br>
</div>
<div class="moz-cite-prefix"> This will be exactly the same
results with the same limitations (Halpha redshift and there or
not and NII there or not) but at least less confusion. And you
will exclude all cubes which are not organized with velocity axes
anyway.</div>
<div class="moz-cite-prefix"> I still wonder if the em_unit is
needed there, because it is supposed to describe the unit used in
the dataset and I don't think if you look for velocity cubes you
want to select those in m/s from those in km/s. I think what you
need is to know what is the unit.</div>
<div class="moz-cite-prefix"> <br>
</div>
<div class="moz-cite-prefix"> My conclusion adding em_ref for
the reference line an a couple of new values for em_ucd should be
enough for ObsCore extension and all the other things for SODA.<br>
</div>
<div class="moz-cite-prefix"><br>
</div>
<div class="moz-cite-prefix"><br>
</div>
<div class="moz-cite-prefix">Cheers</div>
<div class="moz-cite-prefix">François<br>
</div>
<div class="moz-cite-prefix"> <br>
</div>
<div class="moz-cite-prefix"> <br>
</div>
<div class="moz-cite-prefix"> <br>
</div>
<div class="moz-cite-prefix"><br>
</div>
<div class="moz-cite-prefix">Le 22/02/2023 à 17:33, Alberto Micol a
écrit :<br>
</div>
<blockquote type="cite"
cite="mid:F363D9DA-6F8B-44B0-A47E-AD1051A705E2@eso.org">
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<p class="MsoNormal"><span style="mso-fareast-language:EN-US">Sorry
let me rephrase more correctly:<o:p></o:p></span></p>
<p class="MsoNormal"><span style="mso-fareast-language:EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="mso-fareast-language:EN-US">Can
we aim to describe the Greisen (2006) cubes, limiting to the
3d case (2 spatial 1 velocity), so to cover most of the
existing velocity cubes?<o:p></o:p></span></p>
<p class="MsoNormal"><span style="mso-fareast-language:EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="mso-fareast-language:EN-US">Thanks,<o:p></o:p></span></p>
<p class="MsoNormal"><span style="mso-fareast-language:EN-US">Alberto<o:p></o:p></span></p>
<p class="MsoNormal"><span style="mso-fareast-language:EN-US"><o:p> </o:p></span></p>
<div style="border:none;border-top:solid #B5C4DF
1.0pt;padding:3.0pt 0cm 0cm 0cm">
<p class="MsoNormal"><b><span
style="font-size:12.0pt;color:black">From: </span></b><span
style="font-size:12.0pt;color:black">Alberto Micol
<a class="moz-txt-link-rfc2396E" href="mailto:amicol@eso.org"><amicol@eso.org></a><br>
<b>Date: </b>Wednesday, 22 February 2023 at 17:26<br>
<b>To: </b>BONNAREL FRANCOIS
<a class="moz-txt-link-rfc2396E" href="mailto:francois.bonnarel@astro.unistra.fr"><francois.bonnarel@astro.unistra.fr></a>, alberto micol
<a class="moz-txt-link-rfc2396E" href="mailto:amicol.ivoa@googlemail.com"><amicol.ivoa@googlemail.com></a><br>
<b>Cc: </b><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>, Data
Models mailing list <a class="moz-txt-link-rfc2396E" href="mailto:dm@ivoa.net"><dm@ivoa.net></a><br>
<b>Subject: </b>Re: ObsCore for velocity cubes<o:p></o:p></span></p>
</div>
<div>
<p class="MsoNormal"><o:p> </o:p></p>
</div>
<p class="MsoNormal"><span style="mso-fareast-language:EN-US">Thanks
for the explanation!</span><o:p></o:p></p>
<p class="MsoNormal"><span style="mso-fareast-language:EN-US">As
said, my aim is to cover the cubes described in Greisen et
al, 2006, and not “any kind of imaginable cube”.</span><o:p></o:p></p>
<p class="MsoNormal"><span style="mso-fareast-language:EN-US">This
4D cube you described is something of a different nature.
And indeed is no longer a regular 3D cube.</span><o:p></o:p></p>
<p class="MsoNormal"><span style="mso-fareast-language:EN-US">Can’t
we aim to describe just only the Greisen et al, 3d cubes?
</span><o:p></o:p></p>
<p class="MsoNormal"><span style="mso-fareast-language:EN-US">That
would cover a huge fraction of the existing cubes.</span><o:p></o:p></p>
<p class="MsoNormal"><span style="mso-fareast-language:EN-US"> </span><o:p></o:p></p>
<p class="MsoNormal"><span style="mso-fareast-language:EN-US">Thanks,</span><o:p></o:p></p>
<p class="MsoNormal"><span style="mso-fareast-language:EN-US">Alberto</span><o:p></o:p></p>
<p class="MsoNormal"><span style="mso-fareast-language:EN-US"> </span><o:p></o:p></p>
<div style="border:none;border-top:solid #B5C4DF
1.0pt;padding:3.0pt 0cm 0cm 0cm">
<p class="MsoNormal"><b><span
style="font-size:12.0pt;color:black">From: </span></b><span
style="font-size:12.0pt;color:black">BONNAREL FRANCOIS
<a class="moz-txt-link-rfc2396E" href="mailto:francois.bonnarel@astro.unistra.fr"><francois.bonnarel@astro.unistra.fr></a><br>
<b>Date: </b>Wednesday, 22 February 2023 at 17:20<br>
<b>To: </b>Alberto Micol <a class="moz-txt-link-rfc2396E" href="mailto:amicol@eso.org"><amicol@eso.org></a>, alberto
micol <a class="moz-txt-link-rfc2396E" href="mailto:amicol.ivoa@googlemail.com"><amicol.ivoa@googlemail.com></a><br>
<b>Cc: </b><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>, Data
Models mailing list <a class="moz-txt-link-rfc2396E" href="mailto:dm@ivoa.net"><dm@ivoa.net></a><br>
<b>Subject: </b>Re: ObsCore for velocity cubes</span><o:p></o:p></p>
</div>
<div>
<p class="MsoNormal"> <o:p></o:p></p>
</div>
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<p class="MsoNormal"><span
style="font-size:10.0pt;font-family:"Arial",sans-serif">This
email was sent from outside of ESO from the address
<strong><span
style="font-family:"Arial",sans-serif;color:black">[<a class="moz-txt-link-abbreviated" href="mailto:francois.bonnarel@astro.unistra.fr">francois.bonnarel@astro.unistra.fr</a>]</span></strong><span
style="color:black">. If it looks suspicious,
please report it to <a class="moz-txt-link-abbreviated" href="mailto:phishing@eso.org">phishing@eso.org</a>.</span></span><o:p></o:p></p>
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<p class="MsoNormal"><span style="color:white"> </span><o:p></o:p></p>
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<div>
<p class="MsoNormal"><span style="color:white">Dear Albe</span>rto,<o:p></o:p></p>
</div>
<div>
<p class="MsoNormal">I quote Arnold (2015 Apr 30)<o:p></o:p></p>
</div>
<div>
<blockquote style="margin-top:5.0pt;margin-bottom:5.0pt">
<pre>I strongly urge to keep the two separate.<o:p></o:p></pre>
<pre>Yes, they have much in common, but they serve very different purposes.<o:p></o:p></pre>
<pre>And it is possible to create a 4-D cube where the 4th axis is actually a<o:p></o:p></pre>
<pre>spectral axis and the pixels are different lines (rest frequencies).<o:p></o:p></pre>
<pre>STC2 will treat the spectral and redshift/Doppler as distinct axes.<o:p></o:p></pre>
</blockquote>
<p class="MsoNormal">Now imagine you have Halpha and Hbeta
lines in the same dataset (MUSE cubes?). The may come from
different regions and the velocities will be different for
both.<o:p></o:p></p>
</div>
<div>
<p class="MsoNormal">You could have a different velocity map
for the two lines in the same dataset.<o:p></o:p></p>
</div>
<div>
<p class="MsoNormal">Cheers<o:p></o:p></p>
</div>
<div>
<p class="MsoNormal">François <o:p></o:p></p>
</div>
<div>
<p class="MsoNormal"> <o:p></o:p></p>
</div>
<div>
<p class="MsoNormal">Le 22/02/2023 à 17:06, Alberto Micol a
écrit :<o:p></o:p></p>
</div>
<blockquote style="margin-top:5.0pt;margin-bottom:5.0pt">
<p class="MsoNormal"><span style="mso-fareast-language:EN-US">Many
thanks François,</span><o:p></o:p></p>
<p class="MsoNormal"><span style="mso-fareast-language:EN-US"> </span><o:p></o:p></p>
<p class="MsoNormal"><span style="mso-fareast-language:EN-US">I
will think thouroughly through your message, but first I
would like to ask you to clarify the meaning of your
sentence: “As Arnold pointed at that time you have
datasets where you provide different doppler shift
information at different spectral coordinates. What are
the radial velocity bounds in that case ?”</span><o:p></o:p></p>
<p class="MsoNormal"><span style="mso-fareast-language:EN-US">Could
you explain that with more words, maybe giving an example?</span><o:p></o:p></p>
<p class="MsoNormal"><span style="mso-fareast-language:EN-US"> </span><o:p></o:p></p>
<p class="MsoNormal"><span style="mso-fareast-language:EN-US">To
explain why I do not understand that sentence, I give you
an example of a cube I have at hand here.</span><o:p></o:p></p>
<p class="MsoNormal"><span style="mso-fareast-language:EN-US"> </span><o:p></o:p></p>
<p class="MsoNormal"><span style="mso-fareast-language:EN-US">In
my case a velocity cube is a FITS cube with the third axis
defined as:</span><o:p></o:p></p>
<p class="MsoNormal"><span style="mso-fareast-language:EN-US">CTYPE3
= ‘VRAD’</span><o:p></o:p></p>
<p class="MsoNormal"><span style="mso-fareast-language:EN-US">CUNIT3
= ‘m/s’</span><o:p></o:p></p>
<p class="MsoNormal"><span style="mso-fareast-language:EN-US">CD3_3_
= 250</span><o:p></o:p></p>
<p class="MsoNormal"><span style="mso-fareast-language:EN-US">CRVAL3
= 0</span><o:p></o:p></p>
<p class="MsoNormal"><span style="mso-fareast-language:EN-US">CRPIX3
= 141</span><o:p></o:p></p>
<p class="MsoNormal"><span style="mso-fareast-language:EN-US">NAXIS3
= 281</span><o:p></o:p></p>
<p class="MsoNormal"><span style="mso-fareast-language:EN-US"> </span><o:p></o:p></p>
<p class="MsoNormal"><span style="mso-fareast-language:EN-US">That
is enough to state that:
</span><o:p></o:p></p>
<p class="MsoNormal"><span style="mso-fareast-language:EN-US">V_min
= -35000 m/s</span><o:p></o:p></p>
<p class="MsoNormal"><span style="mso-fareast-language:EN-US">V_max
= +35000 m/s</span><o:p></o:p></p>
<p class="MsoNormal"><span style="mso-fareast-language:EN-US">Many
thanks,</span><o:p></o:p></p>
<p class="MsoNormal"><span style="mso-fareast-language:EN-US">Alberto</span><o:p></o:p></p>
<p class="MsoNormal"><span style="mso-fareast-language:EN-US"> </span><o:p></o:p></p>
<div style="border:none;border-top:solid #B5C4DF
1.0pt;padding:3.0pt 0cm 0cm 0cm">
<p class="MsoNormal"><b><span
style="font-size:12.0pt;color:black">From: </span></b><span
style="font-size:12.0pt;color:black">BONNAREL FRANCOIS
<a href="mailto:francois.bonnarel@astro.unistra.fr"
moz-do-not-send="true"><francois.bonnarel@astro.unistra.fr></a><br>
<b>Date: </b>Wednesday, 22 February 2023 at 16:46<br>
<b>To: </b>alberto micol <a
href="mailto:amicol.ivoa@googlemail.com"
moz-do-not-send="true"><amicol.ivoa@googlemail.com></a>,
Alberto Micol
<a href="mailto:amicol@eso.org" moz-do-not-send="true"><amicol@eso.org></a><br>
<b>Cc: </b><a href="mailto:dal@ivoa.net"
moz-do-not-send="true">"dal@ivoa.net"</a> <a
href="mailto:dal@ivoa.net" moz-do-not-send="true">
<dal@ivoa.net></a>, Data Models mailing list <a
href="mailto:dm@ivoa.net" moz-do-not-send="true"><dm@ivoa.net></a><br>
<b>Subject: </b>Re: ObsCore for velocity cubes</span><o:p></o:p></p>
</div>
<div>
<p class="MsoNormal"> <o:p></o:p></p>
</div>
<table class="MsoNormalTable" style="width:100.0%"
width="100%" cellspacing="0" cellpadding="0" border="0">
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orange 6.0pt;background:white;padding:7.5pt 7.5pt
7.5pt 7.5pt">
<p class="MsoNormal"><span
style="font-size:10.0pt;font-family:"Arial",sans-serif">This
email was sent from outside of ESO from the
address
<strong><span
style="font-family:"Arial",sans-serif;color:black">[<a
href="mailto:francois.bonnarel@astro.unistra.fr" moz-do-not-send="true"
class="moz-txt-link-freetext">francois.bonnarel@astro.unistra.fr</a>]</span></strong><span
style="color:black">. If it looks suspicious,
please report it to
<a href="mailto:phishing@eso.org"
moz-do-not-send="true"
class="moz-txt-link-freetext">phishing@eso.org</a>.</span></span><o:p></o:p></p>
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<p class="MsoNormal"><span style="color:white"> </span><o:p></o:p></p>
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<div>
<p class="MsoNormal"><span style="color:white">Dear Albe</span>rto,
all,<o:p></o:p></p>
</div>
<div>
<p class="MsoNormal"> <o:p></o:p></p>
</div>
<div>
<p class="MsoNormal"> I come to this copying also to the
dm list (ObsCoire and extensions are dm stuff). As you may
remember this point was EXTENSIVELY discussed when we
upgraded ObsCore from 1.0 to 1.1.<o:p></o:p></p>
</div>
<div>
<p class="MsoNormal"> This discussion was mainly in
2014/2015. See for example these threads starting by
<a
href="http://mail.ivoa.net/pipermail/dm/2015-April/005147.html"
moz-do-not-send="true" class="moz-txt-link-freetext">http://mail.ivoa.net/pipermail/dm/2015-April/005147.html</a>
and
<a
href="http://mail.ivoa.net/pipermail/dm/2015-April/005168.html"
moz-do-not-send="true" class="moz-txt-link-freetext">http://mail.ivoa.net/pipermail/dm/2015-April/005168.html</a>
as well as
<a
href="http://mail.ivoa.net/pipermail/dm/2015-May/005174.html"
moz-do-not-send="true" class="moz-txt-link-freetext">http://mail.ivoa.net/pipermail/dm/2015-May/005174.html</a><o:p></o:p></p>
</div>
<div>
<p class="MsoNormal"> <o:p></o:p></p>
</div>
<div>
<p class="MsoNormal"> The conclusion at that time was
that we didn't have to extend ObsCore this way eventually.<o:p></o:p></p>
</div>
<div>
<p class="MsoNormal"> For several reasons.<o:p></o:p></p>
</div>
<div>
<p class="MsoNormal"> - radial velocity or redshifts
derivation from spectral frequencies or wl are complex
things. querying between vel = 10 km/s and 60 km/s may
give different results according to the radial velocity
(or dopplershift) flavor. And if we add the constraint
em_ucd = vrad (or vopt, or ) then the query become really
specialised.<o:p></o:p></p>
</div>
<div>
<p class="MsoNormal"> - if the velocity cube is simply
a transform of the frequency/wavelength axis we still
have to select on wavelength because velocity cubes in
radio domain and velocity cube in optical domain are
really different things<o:p></o:p></p>
</div>
<div>
<p class="MsoNormal"> - But generally speaking the
velocity axis is not ONLY a transform of the wavelength
(or frequency) axis, it provides different information. It
is a different axis (although related). As Arnold pointed
at that time you have datasets where you provide different
doppler shift information at different spectral
coordinates. What are the radial velocity bounds in that
case ?<o:p></o:p></p>
</div>
<div>
<p class="MsoNormal"> ---> ObsCore will become
really complex to manage and fill in these situations<o:p></o:p></p>
</div>
<div>
<p class="MsoNormal"> <o:p></o:p></p>
</div>
<div>
<p class="MsoNormal"> Considering your use case
Alberto, I think we have two distinguish two steps<o:p></o:p></p>
</div>
<div>
<p class="MsoNormal"> - data discovery (With
ObsTAP/ SIA) = it's probably enough to let the user know
that you have velocity cubes by providing the appropriate
values in em_ucd and em_unit (which are there to describe
the dataset content and not the spectral
characterization). We may think to add em_ref to give the
wl of the reference line. velocity limits will have to
be transformed in wavelength to fill the mandatory
em_min/max anyway. With this you already know that the
data you discover by a standard ObsCore (or radio
extension) query are "'velocity cubes"<o:p></o:p></p>
</div>
<div>
<p class="MsoNormal"> <o:p></o:p></p>
</div>
<div>
<p class="MsoNormal"> - SODA cutouts : there ,
the parameters you propose are useful. A discussion
started already some time ago to extend SODA . For example
adding pixel cutouts, or changing the projection or the
spatial sampling of the cutout. In this context we could
also choose to extract by forcing velocity constraints,
when appropro$iate.
<o:p></o:p></p>
</div>
<div>
<p class="MsoNormal"> To do that we need
additional metadata (eg : the content of WCS, and this
also for the spectral axis). And for that, there is the
old idea to have a SODA mode providing full metadata, CADC
already implemented something like that. The velocity
'"axis" detailed flavor can be described this way if it
exists. This also has to be integrated in the SODA-next
discussion. Some more on this will come soon.<o:p></o:p></p>
</div>
<div>
<p class="MsoNormal"> <o:p></o:p></p>
</div>
<div>
<p class="MsoNormal">Cheers<o:p></o:p></p>
</div>
<div>
<p class="MsoNormal">François<o:p></o:p></p>
</div>
<div>
<p class="MsoNormal"> <o:p></o:p></p>
</div>
<div>
<p class="MsoNormal"> <o:p></o:p></p>
</div>
<div>
<p class="MsoNormal"> 1Le 22/02/2023 à 11:33, alberto micol
a écrit :<o:p></o:p></p>
</div>
<blockquote style="margin-top:5.0pt;margin-bottom:5.0pt">
<p class="MsoNormal">Very well, thanks both Markus and Pat.
<o:p></o:p></p>
<div>
<p class="MsoNormal"> <o:p></o:p></p>
</div>
<div>
<p class="MsoNormal">So, yes, we need a v_resolution, and
it must be in fixed units.<o:p></o:p></p>
</div>
<div>
<p class="MsoNormal">Taking the Greisen et al. default,
this is [m/s].<o:p></o:p></p>
</div>
<div>
<p class="MsoNormal"> <o:p></o:p></p>
</div>
<div>
<p class="MsoNormal">We though need the fravergy UCD to be
able to discriminate the different velocity flavours.<o:p></o:p></p>
</div>
<div>
<p class="MsoNormal">Is em_ucd the correct field to use? <o:p></o:p></p>
</div>
<div>
<p class="MsoNormal">(Yes, I’m hit strongly by the
confusion of throwing untested features from a data
model into a relational mapping,<o:p></o:p></p>
</div>
<div>
<p class="MsoNormal">that’s why I need your confirmation
on this)<o:p></o:p></p>
</div>
<div>
<p class="MsoNormal"> <o:p></o:p></p>
</div>
<div>
<p class="MsoNormal">Thanks!<o:p></o:p></p>
</div>
<div>
<p class="MsoNormal">Alberto<o:p></o:p></p>
</div>
<div>
<p class="MsoNormal"> <o:p></o:p></p>
</div>
<div>
<p class="MsoNormal"> <o:p></o:p></p>
</div>
<div>
<div>
<div>
<blockquote
style="margin-top:5.0pt;margin-bottom:5.0pt">
<div>
<p class="MsoNormal">On 21 Feb 2023, at 21:11,
Alberto Micol <<a
href="mailto:amicol@eso.org"
moz-do-not-send="true"
class="moz-txt-link-freetext">amicol@eso.org</a>>
wrote:<o:p></o:p></p>
</div>
<p class="MsoNormal"> <o:p></o:p></p>
<div>
<div>
<p class="MsoNormal"><span
style="font-size:10.5pt;font-family:Helvetica">Hi
James,</span><o:p></o:p></p>
</div>
<div>
<p class="MsoNormal"><span
style="font-size:10.5pt;font-family:Helvetica"> </span><o:p></o:p></p>
</div>
<div>
<p class="MsoNormal"><span
style="font-size:10.5pt;font-family:Helvetica">Thanks
for the answer. I have a question/doubt
regarding the v_resolution and v_unit.</span><o:p></o:p></p>
</div>
<div>
<p class="MsoNormal"><span
style="font-size:10.5pt;font-family:Helvetica"> </span><o:p></o:p></p>
</div>
<div>
<p class="MsoNormal"><span
style="font-size:10.5pt;font-family:Helvetica">ObsCore
already foresees the em_resolution, so I
originally thought we do not need the
v_resolution.</span><o:p></o:p></p>
</div>
<div>
<p class="MsoNormal"><span
style="font-size:10.5pt;font-family:Helvetica"> </span><o:p></o:p></p>
</div>
<div>
<p class="MsoNormal"><span
style="font-size:10.5pt;font-family:Helvetica">But
now I am reconsidering this, because I think
(in the ObsCore standard we were not
super-clear regarding this) the units of
em_resolution are the ones provided by the
em_unit attribute. Different cubes could
have different em_units, and that means that
em_resolution could not be used to
seamlessly query across all possible cubes.</span><o:p></o:p></p>
</div>
<div>
<p class="MsoNormal"><span
style="font-size:10.5pt;font-family:Helvetica"> </span><o:p></o:p></p>
</div>
<div>
<p class="MsoNormal"><span
style="font-size:10.5pt;font-family:Helvetica">If
the above is correct, then, yes, we need to
have a new field,</span><o:p></o:p></p>
</div>
<div>
<p class="MsoNormal"><span
style="font-size:10.5pt;font-family:Helvetica">v_resolution,
with units fixed to e.g. m/s,</span><o:p></o:p></p>
</div>
<div>
<p class="MsoNormal"><span
style="font-size:10.5pt;font-family:Helvetica">similarly
to the case of em_min/max always provided in
[m], whatever the value of the em_unit, to
support searches.</span><o:p></o:p></p>
</div>
<div>
<p class="MsoNormal"><span
style="font-size:10.5pt;font-family:Helvetica"> </span><o:p></o:p></p>
</div>
<div>
<p class="MsoNormal"><span
style="font-size:10.5pt;font-family:Helvetica">In
which case, we do not need a v_unit, as
v_min/max are fixed in [m/s] and we already
have em_unit for the units encoded in the
cube.</span><o:p></o:p></p>
</div>
<div>
<p class="MsoNormal"><span
style="font-size:10.5pt;font-family:Helvetica"> </span><o:p></o:p></p>
</div>
<div>
<p class="MsoNormal"><span
style="font-size:10.5pt;font-family:Helvetica">Would
that make sense?</span><o:p></o:p></p>
</div>
<div>
<p class="MsoNormal"><span
style="font-size:10.5pt;font-family:Helvetica"> </span><o:p></o:p></p>
</div>
<div>
<p class="MsoNormal"><span
style="font-size:10.5pt;font-family:Helvetica">Regarding
treating frequency cubes as velocity cubes
(and viceversa), </span><o:p></o:p></p>
</div>
<div>
<p class="MsoNormal"><span
style="font-size:10.5pt;font-family:Helvetica">it
is indeed useful to provide
characterisations both in frequency and in
velocity</span><o:p></o:p></p>
</div>
<div>
<p class="MsoNormal"><span
style="font-size:10.5pt;font-family:Helvetica">(and
why not energy and wavelength),
distinguishing the different cases according
to</span><o:p></o:p></p>
</div>
<div>
<p class="MsoNormal"><span
style="font-size:10.5pt;font-family:Helvetica">the
value of the em_ucd, e.g., em.freq,
em.wl, em.energy (see ObsCore B.6.2), or</span><o:p></o:p></p>
</div>
<div>
<p class="MsoNormal"><span
style="font-size:10.5pt;font-family:Helvetica">spect.dopplerVeloc.radio, spect.dopplerVeloc.opt, spect.dopplerVeloc.rel
(*) (see ObsCore B.6.2.6). </span><o:p></o:p></p>
</div>
<div>
<p class="MsoNormal"><span
style="font-size:10.5pt;font-family:Helvetica"> </span><o:p></o:p></p>
</div>
<div>
<p class="MsoNormal"><span
style="font-size:10.5pt;font-family:Helvetica">So
we would have:</span><o:p></o:p></p>
</div>
<div>
<p class="MsoNormal"><span
style="font-size:10.5pt;font-family:Helvetica"> </span><o:p></o:p></p>
</div>
<div>
<p class="MsoNormal"><span
style="font-size:10.5pt;font-family:Helvetica">em_ucd
required</span><o:p></o:p></p>
</div>
<div>
<p class="MsoNormal"><span
style="font-size:10.5pt;font-family:Helvetica">v_resolution
required, fixed in m/s</span><o:p></o:p></p>
</div>
<div>
<p class="MsoNormal"><span
style="font-size:10.5pt;font-family:Helvetica">em_unit
optional, expressing the unit encoded in the
cube for the spectral axis</span><o:p></o:p></p>
</div>
<div>
<p class="MsoNormal"><span
style="font-size:10.5pt;font-family:Helvetica">em_resolution
optional, expressing the resolution in the
units used by the data cube</span><o:p></o:p></p>
</div>
<div>
<p class="MsoNormal"><span
style="font-size:10.5pt;font-family:Helvetica"> </span><o:p></o:p></p>
</div>
<div>
<p class="MsoNormal"><span
style="font-size:10.5pt;font-family:Helvetica">If
we converge on this, I could put together a
little document with a detailed proposal.</span><o:p></o:p></p>
</div>
<div>
<p class="MsoNormal"><span
style="font-size:10.5pt;font-family:Helvetica">Would
that considered useful?</span><o:p></o:p></p>
</div>
<div>
<p class="MsoNormal"><span
style="font-size:10.5pt;font-family:Helvetica"> </span><o:p></o:p></p>
</div>
<div>
<p class="MsoNormal"><span
style="font-size:10.5pt;font-family:Helvetica">Cheers,</span><o:p></o:p></p>
</div>
<div>
<p class="MsoNormal"><span
style="font-size:10.5pt;font-family:Helvetica">Alberto</span><o:p></o:p></p>
</div>
<div>
<p class="MsoNormal"><span
style="font-size:10.5pt;font-family:Helvetica"> </span><o:p></o:p></p>
</div>
<div>
<p class="MsoNormal"><span
style="font-size:10.5pt;font-family:Helvetica">(*)
cross-standard issue: the
spect.dopplerVeloc.rel is mentioned in the
ObsCore standard, </span><o:p></o:p></p>
</div>
<div>
<p class="MsoNormal"><span
style="font-size:10.5pt;font-family:Helvetica">but
it is not a recognised value in the current
UCD1+ standard.</span><o:p></o:p></p>
</div>
<div>
<p class="MsoNormal"><span
style="font-size:10.5pt;font-family:Helvetica">We
will need to act on this (Mireille?).</span><o:p></o:p></p>
</div>
<div>
<p class="MsoNormal"> <o:p></o:p></p>
</div>
<div style="border:none;border-top:solid #B5C4DF
1.0pt;padding:3.0pt 0cm 0cm 0cm">
<div>
<p class="MsoNormal"><b><span
style="font-size:12.0pt">From:<span
class="apple-converted-space"> </span></span></b><span
style="font-size:12.0pt">"Dempsey, James
(IM&T, Black Mountain)" <<a
href="mailto:James.Dempsey@csiro.au"
moz-do-not-send="true"><span
style="color:purple">James.Dempsey@csiro.au</span></a>><br>
<b>Date:<span
class="apple-converted-space"> </span></b>Thursday,
16 February 2023 at 00:21<br>
<b>To:<span class="apple-converted-space"> </span></b>Alberto
Micol <<a href="mailto:amicol@eso.org"
moz-do-not-send="true"><span
style="color:purple">amicol@eso.org</span></a>>,
"<a href="mailto:dal@ivoa.net"
moz-do-not-send="true"><span
style="color:purple">dal@ivoa.net</span></a>"
<<a href="mailto:dal@ivoa.net"
moz-do-not-send="true"><span
style="color:purple">dal@ivoa.net</span></a>><br>
<b>Subject:<span
class="apple-converted-space"> </span></b>Re:
ObsCore for velocity cubes</span><o:p></o:p></p>
</div>
</div>
<div>
<div>
<p class="MsoNormal"> <o:p></o:p></p>
</div>
</div>
<table class="MsoNormalTable" style="width:100.0%"
width="100%" cellspacing="0" cellpadding="0"
border="0">
<tbody>
<tr>
<td style="border:solid orange
1.0pt;border-left:solid orange
6.0pt;background:white;padding:7.5pt 7.5pt
7.5pt 7.5pt;background-position:initial
initial;background-repeat:initial initial">
<div>
<p class="MsoNormal"><span
style="font-size:10.0pt;font-family:"Arial",sans-serif">Th<span
style="color:black">is email was
sent from outside of ESO from the
address<strong><span
style="font-family:"Arial",sans-serif">[<a
href="mailto:prvs=40330730a=James.Dempsey@csiro.au"
moz-do-not-send="true"><span
style="color:purple">prvs=40330730a=James.Dempsey@csiro.au</span></a>]</span></strong>. If
it looks suspicious, please report
it to<span
class="apple-converted-space"> </span><a
href="mailto:phishing@eso.org"
moz-do-not-send="true"><span
style="color:purple">phishing@eso.org</span></a>.</span></span><o:p></o:p></p>
</div>
</td>
</tr>
</tbody>
</table>
<p class="MsoNormal"><span
style="font-size:9.0pt;font-family:Helvetica;color:white"> </span><o:p></o:p></p>
<table class="MsoNormalTable" cellspacing="0"
cellpadding="0" border="0">
<tbody>
<tr style="height:7.5pt">
<td style="width:100.0%;padding:0cm 0cm 0cm
0cm;height:7.5pt" width="100%">
<div>
<p class="MsoNormal"
style="line-height:7.5pt"><span
style="font-size:7.5pt"> </span><o:p></o:p></p>
</div>
</td>
</tr>
</tbody>
</table>
<div>
<p class="MsoNormal"><span style="color:white">Hi
Alberto</span>,<o:p></o:p></p>
</div>
<div>
<p class="MsoNormal"> <o:p></o:p></p>
</div>
<div>
<p class="MsoNormal">At CASDA we support cutouts
of velocity spectral line cubes.<o:p></o:p></p>
</div>
<div>
<p class="MsoNormal"> <o:p></o:p></p>
</div>
<div>
<p class="MsoNormal">We currently require the
user to provide a BAND or CHANNEL parameter to
the SODA service which is translated by the
service to the velocity frame of the target
cube. This works, but requiring conversions on
both the client and server side isn’t ideal.
Likewise, in our ObsCore implementation only
the em_ucd indicates the cubes are in velocity
but it would certainly be useful to have full
velocity information for data discovery!<o:p></o:p></p>
</div>
<div>
<p class="MsoNormal"> <o:p></o:p></p>
</div>
<div>
<p class="MsoNormal">The extension you outline
looks like it would work nicely for the same
use case in CASDA. However I think we should
add the following to fully describe the
velocity axis (as opposed to its translation
into wavelength for the base obscore).<o:p></o:p></p>
</div>
<ol style="margin-top:0cm" type="1" start="1">
<li class="MsoListParagraph"
style="margin-top:0cm;margin-bottom:0cm;margin-bottom:.0001pt;mso-list:l0
level1 lfo3">
v_resolution – value of CDELT3 or CDELT4<span
style="font-size:10.0pt"> </span><o:p></o:p></li>
<li class="MsoListParagraph"
style="margin-top:0cm;margin-bottom:0cm;margin-bottom:.0001pt;mso-list:l0
level1 lfo3">
v_unit – although this should always be m/s<span
style="font-size:10.0pt"> </span>
<o:p></o:p></li>
</ol>
<div>
<p class="MsoNormal"> <o:p></o:p></p>
</div>
<div>
<p class="MsoNormal">Another consideration is
that a lot of our users tend to use velocity
to interact with frequency cubes. So even for
these frequency cubes we might end up filling
in velocity metadata if the fields were
defined. Tools such as CARTA tend to
automatically show the spectral axis as
velocity where it can, such that many users
would assume the cubes are in velocity not
frequency.<o:p></o:p></p>
</div>
<div>
<p class="MsoNormal"> <o:p></o:p></p>
</div>
<div>
<div>
<div>
<p class="MsoNormal">Cheers,<o:p></o:p></p>
</div>
<div>
<p class="MsoNormal"><b><span
style="color:#00A9CE">James Dempsey</span></b><o:p></o:p></p>
</div>
<div>
<p class="MsoNormal"><span
style="font-size:9.0pt">Senior
Developer <span
class="apple-converted-space"> </span>|
CSIRO </span><o:p></o:p></p>
</div>
<div>
<p class="MsoNormal"><a
href="mailto:james.dempsey@csiro.au"
moz-do-not-send="true"><span
style="font-size:9.0pt;color:purple">james.dempsey@csiro.au</span></a><span
style="font-size:9.0pt"> <span
class="apple-converted-space"> </span>|
02 6214 2912</span><o:p></o:p></p>
</div>
</div>
</div>
<div>
<p class="MsoNormal"> <o:p></o:p></p>
</div>
<div>
<p class="MsoNormal"> <o:p></o:p></p>
</div>
<div style="border:none;border-top:solid #B5C4DF
1.0pt;padding:3.0pt 0cm 0cm 0cm">
<p class="MsoNormal"
style="margin-bottom:12.0pt"><b><span
style="font-size:12.0pt">From:<span
class="apple-converted-space"> </span></span></b><span
style="font-size:12.0pt">dal <<a
href="mailto:dal-bounces@ivoa.net"
moz-do-not-send="true"
class="moz-txt-link-freetext">dal-bounces@ivoa.net</a>>
on behalf of alberto micol <<a
href="mailto:amicol.ivoa@googlemail.com"
moz-do-not-send="true"
class="moz-txt-link-freetext">amicol.ivoa@googlemail.com</a>><br>
<b>Date:<span class="apple-converted-space"> </span></b>Thursday,
16 February 2023 at 12:02 am<br>
<b>To:<span class="apple-converted-space"> </span></b><a
href="mailto:dal@ivoa.net"
moz-do-not-send="true"
class="moz-txt-link-freetext">dal@ivoa.net</a>
<<a href="mailto:dal@ivoa.net"
moz-do-not-send="true"
class="moz-txt-link-freetext">dal@ivoa.net</a>><br>
<b>Subject:<span
class="apple-converted-space"> </span></b>ObsCore
for velocity cubes</span><o:p></o:p></p>
</div>
<div>
<p class="MsoNormal">Dear ObsCorers,<o:p></o:p></p>
</div>
<div>
<div>
<p class="MsoNormal"> <o:p></o:p></p>
</div>
</div>
<div>
<div>
<p class="MsoNormal">I have received with much
interest the ObsCore extension for RADIO
data, thanks for that very clear document.<o:p></o:p></p>
</div>
</div>
<div>
<div>
<p class="MsoNormal"> <o:p></o:p></p>
</div>
</div>
<div>
<div>
<p class="MsoNormal">Would it be possible to
have a similar extension for cubes with
velocity as third axis (the other two being
the usual spatial ones)?<o:p></o:p></p>
</div>
</div>
<div>
<div>
<p class="MsoNormal">Let me call them
“velocity cubes”...<o:p></o:p></p>
</div>
</div>
<div>
<div>
<p class="MsoNormal"> <o:p></o:p></p>
</div>
</div>
<div>
<div>
<p class="MsoNormal">Here my use case…<o:p></o:p></p>
</div>
</div>
<div>
<div>
<p class="MsoNormal"> <o:p></o:p></p>
</div>
</div>
<div>
<div>
<p class="MsoNormal">At ESO we need to support
cutouts of velocity cubes.<o:p></o:p></p>
</div>
</div>
<div>
<div>
<p class="MsoNormal"> <o:p></o:p></p>
</div>
</div>
<div>
<div>
<p class="MsoNormal">Up to now our SODA
interface supported spectra, images, and
wavelength cubes;<o:p></o:p></p>
</div>
</div>
<div>
<div>
<p class="MsoNormal">to provide the user with
the SODA input parameters and their possible
MIN/MAX values<o:p></o:p></p>
</div>
</div>
<div>
<div>
<p class="MsoNormal">we query ivoa.ObsCore.<o:p></o:p></p>
</div>
</div>
<div>
<div>
<p class="MsoNormal"> <o:p></o:p></p>
</div>
</div>
<div>
<div>
<p class="MsoNormal">Now with the introduction
of velocity cubes, we would like to get the
necessary SODA input params also from
ObsCore.<o:p></o:p></p>
</div>
</div>
<div>
<div>
<p class="MsoNormal">We can certainly do so by
extending our own ObsCore table (ObsCore
allows to extend the table), but I was
wondering<o:p></o:p></p>
</div>
</div>
<div>
<div>
<p class="MsoNormal">if others have similar
needs, and see if we can agree with a common
ObsCore extension.<o:p></o:p></p>
</div>
</div>
<div>
<div>
<p class="MsoNormal"> <o:p></o:p></p>
</div>
</div>
<div>
<div>
<p class="MsoNormal">Velocity cubes should
come in a FITS format as described by
Greisen et al, 2006, so-called Paper 3.<o:p></o:p></p>
</div>
</div>
<blockquote
style="margin-left:30.0pt;margin-top:5.0pt;margin-right:0cm;margin-bottom:5.0pt">
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<p class="MsoNormal">Shortly summarised, the
velocity can be either:<o:p></o:p></p>
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</blockquote>
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<ol style="margin-top:0cm" type="1" start="1">
<ol style="margin-top:0cm" type="1" start="1">
<li class="MsoNormal" style="mso-list:l1
level2 lfo6">a radio (VRAD), <span
style="font-size:10.0pt">
</span><o:p></o:p></li>
<li class="MsoNormal" style="mso-list:l1
level2 lfo6">an optical (VOPT), <span
style="font-size:10.0pt">
</span><o:p></o:p></li>
<li class="MsoNormal" style="mso-list:l1
level2 lfo6">a relativistic velocity
(ZOPT), <span style="font-size:10.0pt">
</span><o:p></o:p></li>
<li class="MsoNormal" style="mso-list:l1
level2 lfo6">a generic apparent velocity
(VELO).<span style="font-size:10.0pt">
</span><o:p></o:p></li>
</ol>
</ol>
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<blockquote
style="margin-left:30.0pt;margin-top:5.0pt;margin-right:0cm;margin-bottom:5.0pt">
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<div>
<p class="MsoNormal">The RESTFRQa (RESTWAVa)
keyword conveys the necessary reference
frequency (wavelength) to transform
velocity into frequency or wavelength. <o:p></o:p></p>
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<div>
<p class="MsoNormal">The velocity unit is
m/s.<o:p></o:p></p>
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</blockquote>
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<p class="MsoNormal"> <o:p></o:p></p>
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<p class="MsoNormal">SODA cutouts on the
velocity axis are usually formulated by
passing cuts already expressed in velocity<o:p></o:p></p>
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<div>
<p class="MsoNormal">though it must be
possible to perform the conversions to and
from frequency/wavelength.<o:p></o:p></p>
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<div>
<p class="MsoNormal"> <o:p></o:p></p>
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</div>
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<div>
<p class="MsoNormal">What would then be needed
in ObsCore is:<o:p></o:p></p>
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<p class="MsoNormal"> <o:p></o:p></p>
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<div>
<p class="MsoNormal">v_min<o:p></o:p></p>
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<p class="MsoNormal">v_max<o:p></o:p></p>
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<p class="MsoNormal"> <o:p></o:p></p>
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<div>
<p class="MsoNormal">but also, in case of
radio velocity cube:<o:p></o:p></p>
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</div>
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<div>
<p class="MsoNormal">f_min<o:p></o:p></p>
</div>
</div>
<div>
<div>
<p class="MsoNormal">f_max (getting these from
the RADIO extension)<o:p></o:p></p>
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</div>
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<div>
<p class="MsoNormal">f_rest = RESTFRQ<o:p></o:p></p>
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<div>
<div>
<p class="MsoNormal"> <o:p></o:p></p>
</div>
</div>
<div>
<div>
<p class="MsoNormal">and, in case of a optical
or relativistic velocity cube<o:p></o:p></p>
</div>
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<div>
<p class="MsoNormal">em_rest = RESTWAV<o:p></o:p></p>
</div>
</div>
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<div>
<p class="MsoNormal">(we already have em_min,
em_max)<o:p></o:p></p>
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<div>
<p class="MsoNormal"> <o:p></o:p></p>
</div>
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<div>
<p class="MsoNormal">The em_resolv_power
should then be set to:<o:p></o:p></p>
</div>
</div>
<div>
<div>
<p class="MsoNormal"> lambda
freq c<o:p></o:p></p>
</div>
</div>
<div>
<div>
<p class="MsoNormal"> ——————— = ————— =
—————<o:p></o:p></p>
</div>
</div>
<div>
<div>
<p class="MsoNormal"> delta lambda
delta freq 2 * delta_v<o:p></o:p></p>
</div>
</div>
<div>
<div>
<p class="MsoNormal"> <o:p></o:p></p>
</div>
</div>
<div>
<div>
<p class="MsoNormal">where delta_v is the
CD3_3 in the cube (in the example of a cube
with the velocity on the third axis);<o:p></o:p></p>
</div>
</div>
<div>
<div>
<p class="MsoNormal">but I would also likely
accept a v_pixel_scale (= delta_v).<o:p></o:p></p>
</div>
</div>
<div>
<div>
<p class="MsoNormal"> <o:p></o:p></p>
</div>
</div>
<div>
<div>
<p class="MsoNormal">The UCD for the velocity
should then be:<o:p></o:p></p>
</div>
</div>
<div>
<pre>spect.dopplerVeloc.opt<o:p></o:p></pre>
<div>
<pre>spect.dopplerVeloc.radio<o:p></o:p></pre>
<div>
<div>
<p class="MsoNormal">unsure what it should
be for the relativistic case.<o:p></o:p></p>
</div>
</div>
</div>
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<div>
<div>
<p class="MsoNormal"> <o:p></o:p></p>
</div>
</div>
<div>
<div>
<p class="MsoNormal">This would allow us at
ESO to implement SODA on top of ObsCore (as
already done for all other parameters)<o:p></o:p></p>
</div>
</div>
<div>
<div>
<p class="MsoNormal">and would allow
astronomer to search the velocity cubes with
certain characteristics using ObsCore.<o:p></o:p></p>
</div>
</div>
<div>
<div>
<p class="MsoNormal"> <o:p></o:p></p>
</div>
</div>
<div>
<div>
<p class="MsoNormal">What do you think? <o:p></o:p></p>
</div>
</div>
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<div>
<p class="MsoNormal">Is that doable? I think
at ESO we will simply start implementing the
above extra ObsCore parameters (unless you
suggest different names for that),<o:p></o:p></p>
</div>
</div>
<div>
<div>
<p class="MsoNormal">while waiting to see if
there is more interest to build a proper
standard.<o:p></o:p></p>
</div>
</div>
<div>
<div>
<p class="MsoNormal"> <o:p></o:p></p>
</div>
</div>
<div>
<div>
<p class="MsoNormal">Eager to know what you
think, <o:p></o:p></p>
</div>
</div>
<div>
<div>
<p class="MsoNormal">Cheers,<o:p></o:p></p>
</div>
</div>
<div>
<div>
<p class="MsoNormal">Alberto<o:p></o:p></p>
</div>
</div>
</div>
</blockquote>
</div>
<p class="MsoNormal"> <o:p></o:p></p>
</div>
</div>
</blockquote>
<p> <o:p></o:p></p>
</blockquote>
<p> <o:p></o:p></p>
</div>
</blockquote>
<p><br>
</p>
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