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<div class="moz-cite-prefix">Dear Alberto, all,</div>
<div class="moz-cite-prefix"><br>
</div>
<div class="moz-cite-prefix"> 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.</div>
<div class="moz-cite-prefix"> This discussion was mainly in
2014/2015. See for example these threads starting by
<a class="moz-txt-link-freetext" href="http://mail.ivoa.net/pipermail/dm/2015-April/005147.html">http://mail.ivoa.net/pipermail/dm/2015-April/005147.html</a> and
<a class="moz-txt-link-freetext" href="http://mail.ivoa.net/pipermail/dm/2015-April/005168.html">http://mail.ivoa.net/pipermail/dm/2015-April/005168.html</a> as well
as <a class="moz-txt-link-freetext" href="http://mail.ivoa.net/pipermail/dm/2015-May/005174.html">http://mail.ivoa.net/pipermail/dm/2015-May/005174.html</a></div>
<div class="moz-cite-prefix"><br>
</div>
<div class="moz-cite-prefix"> The conclusion at that time was
that we didn't have to extend ObsCore this way eventually.</div>
<div class="moz-cite-prefix"> For several reasons.</div>
<div class="moz-cite-prefix"> - 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.</div>
<div class="moz-cite-prefix"> - 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</div>
<div class="moz-cite-prefix"> - 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 ?</div>
<div class="moz-cite-prefix"> ---> ObsCore will become
really complex to manage and fill in these situations<br>
</div>
<div class="moz-cite-prefix"><br>
</div>
<div class="moz-cite-prefix"> Considering your use case
Alberto, I think we have two distinguish two steps</div>
<div class="moz-cite-prefix"> - 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"</div>
<div class="moz-cite-prefix"><br>
</div>
<div class="moz-cite-prefix"> - 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. <br>
</div>
<div class="moz-cite-prefix"> 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.</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"> 1Le 22/02/2023 à 11:33, alberto micol
a écrit :<br>
</div>
<blockquote type="cite"
cite="mid:2E98235A-E798-4C0D-8BFB-894D85935A8B@googlemail.com">
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
Very well, thanks both Markus and Pat.
<div class=""><br class="">
</div>
<div class="">So, yes, we need a v_resolution, and it must be in
fixed units.</div>
<div class="">Taking the Greisen et al. default, this is [m/s].</div>
<div class=""><br class="">
</div>
<div class="">We though need the fravergy UCD to be able to
discriminate the different velocity flavours.</div>
<div class="">Is em_ucd the correct field to use? </div>
<div class="">(Yes, I’m hit strongly by the confusion of throwing
untested features from a data model into a relational mapping,</div>
<div class="">that’s why I need your confirmation on this)</div>
<div class=""><br class="">
</div>
<div class="">Thanks!</div>
<div class="">Alberto</div>
<div class=""><br class="">
</div>
<div class=""><br class="">
</div>
<div class="">
<div class="">
<div>
<blockquote type="cite" class="">
<div class="">On 21 Feb 2023, at 21:11, Alberto Micol <<a
href="mailto:amicol@eso.org"
class="moz-txt-link-freetext" moz-do-not-send="true">amicol@eso.org</a>>
wrote:</div>
<br class="Apple-interchange-newline">
<div class="">
<div class="WordSection1" style="page: WordSection1;
font-family: Helvetica; font-size: 12px; font-style:
normal; font-variant-caps: normal; font-weight:
normal; letter-spacing: normal; text-align: start;
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0px;">
<div style="margin: 0cm 0cm 0.0001pt; font-size: 10pt;
font-family: Calibri, sans-serif;" class=""><span
style="font-size: 10.5pt; font-family: Helvetica;"
class="">Hi James,</span><span style="font-size:
11pt;" class=""><o:p class=""></o:p></span></div>
<div style="margin: 0cm 0cm 0.0001pt; font-size: 10pt;
font-family: Calibri, sans-serif;" class=""><span
style="font-size: 10.5pt; font-family: Helvetica;"
class=""><o:p class=""> </o:p></span></div>
<div style="margin: 0cm 0cm 0.0001pt; font-size: 10pt;
font-family: Calibri, sans-serif;" class=""><span
style="font-size: 10.5pt; font-family: Helvetica;"
class="">Thanks for the answer. I have a
question/doubt regarding the v_resolution and
v_unit.<o:p class=""></o:p></span></div>
<div style="margin: 0cm 0cm 0.0001pt; font-size: 10pt;
font-family: Calibri, sans-serif;" class=""><span
style="font-size: 10.5pt; font-family: Helvetica;"
class=""><o:p class=""> </o:p></span></div>
<div style="margin: 0cm 0cm 0.0001pt; font-size: 10pt;
font-family: Calibri, sans-serif;" class=""><span
style="font-size: 10.5pt; font-family: Helvetica;"
class="">ObsCore already foresees the
em_resolution, so I originally thought we do not
need the v_resolution.<o:p class=""></o:p></span></div>
<div style="margin: 0cm 0cm 0.0001pt; font-size: 10pt;
font-family: Calibri, sans-serif;" class=""><span
style="font-size: 10.5pt; font-family: Helvetica;"
class=""><o:p class=""> </o:p></span></div>
<div style="margin: 0cm 0cm 0.0001pt; font-size: 10pt;
font-family: Calibri, sans-serif;" class=""><span
style="font-size: 10.5pt; font-family: Helvetica;"
class="">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.<o:p class=""></o:p></span></div>
<div style="margin: 0cm 0cm 0.0001pt; font-size: 10pt;
font-family: Calibri, sans-serif;" class=""><span
style="font-size: 10.5pt; font-family: Helvetica;"
class=""><o:p class=""> </o:p></span></div>
<div style="margin: 0cm 0cm 0.0001pt; font-size: 10pt;
font-family: Calibri, sans-serif;" class=""><span
style="font-size: 10.5pt; font-family: Helvetica;"
class="">If the above is correct, then, yes, we
need to have a new field,<o:p class=""></o:p></span></div>
<div style="margin: 0cm 0cm 0.0001pt; font-size: 10pt;
font-family: Calibri, sans-serif;" class=""><span
style="font-size: 10.5pt; font-family: Helvetica;"
class="">v_resolution, with units fixed to e.g.
m/s,<o:p class=""></o:p></span></div>
<div style="margin: 0cm 0cm 0.0001pt; font-size: 10pt;
font-family: Calibri, sans-serif;" class=""><span
style="font-size: 10.5pt; font-family: Helvetica;"
class="">similarly to the case of em_min/max
always provided in [m], whatever the value of the
em_unit, to support searches.<o:p class=""></o:p></span></div>
<div style="margin: 0cm 0cm 0.0001pt; font-size: 10pt;
font-family: Calibri, sans-serif;" class=""><span
style="font-size: 10.5pt; font-family: Helvetica;"
class=""><o:p class=""> </o:p></span></div>
<div style="margin: 0cm 0cm 0.0001pt; font-size: 10pt;
font-family: Calibri, sans-serif;" class=""><span
style="font-size: 10.5pt; font-family: Helvetica;"
class="">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.<o:p
class=""></o:p></span></div>
<div style="margin: 0cm 0cm 0.0001pt; font-size: 10pt;
font-family: Calibri, sans-serif;" class=""><span
style="font-size: 10.5pt; font-family: Helvetica;"
class=""><o:p class=""> </o:p></span></div>
<div style="margin: 0cm 0cm 0.0001pt; font-size: 10pt;
font-family: Calibri, sans-serif;" class=""><span
style="font-size: 10.5pt; font-family: Helvetica;"
class="">Would that make sense?<o:p class=""></o:p></span></div>
<div style="margin: 0cm 0cm 0.0001pt; font-size: 10pt;
font-family: Calibri, sans-serif;" class=""><span
style="font-size: 10.5pt; font-family: Helvetica;"
class=""><o:p class=""> </o:p></span></div>
<div style="margin: 0cm 0cm 0.0001pt; font-size: 10pt;
font-family: Calibri, sans-serif;" class=""><span
style="font-size: 10.5pt; font-family: Helvetica;"
class="">Regarding treating frequency cubes as
velocity cubes (and viceversa), <o:p class=""></o:p></span></div>
<div style="margin: 0cm 0cm 0.0001pt; font-size: 10pt;
font-family: Calibri, sans-serif;" class=""><span
style="font-size: 10.5pt; font-family: Helvetica;"
class="">it is indeed useful to provide
characterisations both in frequency and in
velocity<o:p class=""></o:p></span></div>
<div style="margin: 0cm 0cm 0.0001pt; font-size: 10pt;
font-family: Calibri, sans-serif;" class=""><span
style="font-size: 10.5pt; font-family: Helvetica;"
class="">(and why not energy and wavelength),
distinguishing the different cases according to<o:p
class=""></o:p></span></div>
<div style="margin: 0cm 0cm 0.0001pt; font-size: 10pt;
font-family: Calibri, sans-serif;" class=""><span
style="font-size: 10.5pt; font-family: Helvetica;"
class="">the value of the em_ucd, e.g., em.freq,
em.wl, em.energy (see ObsCore B.6.2), or<o:p
class=""></o:p></span></div>
<div style="margin: 0cm 0cm 0.0001pt; font-size: 10pt;
font-family: Calibri, sans-serif;" class=""><span
style="font-size: 10.5pt; font-family: Helvetica;"
class="">spect.dopplerVeloc.radio, spect.dopplerVeloc.opt, spect.dopplerVeloc.rel
(*) (see ObsCore B.6.2.6). <o:p class=""></o:p></span></div>
<div style="margin: 0cm 0cm 0.0001pt; font-size: 10pt;
font-family: Calibri, sans-serif;" class=""><span
style="font-size: 10.5pt; font-family: Helvetica;"
class=""><o:p class=""> </o:p></span></div>
<div style="margin: 0cm 0cm 0.0001pt; font-size: 10pt;
font-family: Calibri, sans-serif;" class=""><span
style="font-size: 10.5pt; font-family: Helvetica;"
class="">So we would have:<o:p class=""></o:p></span></div>
<div style="margin: 0cm 0cm 0.0001pt; font-size: 10pt;
font-family: Calibri, sans-serif;" class=""><span
style="font-size: 10.5pt; font-family: Helvetica;"
class=""><o:p class=""> </o:p></span></div>
<div style="margin: 0cm 0cm 0.0001pt; font-size: 10pt;
font-family: Calibri, sans-serif;" class=""><span
style="font-size: 10.5pt; font-family: Helvetica;"
class="">em_ucd required<o:p class=""></o:p></span></div>
<div style="margin: 0cm 0cm 0.0001pt; font-size: 10pt;
font-family: Calibri, sans-serif;" class=""><span
style="font-size: 10.5pt; font-family: Helvetica;"
class="">v_resolution required, fixed in m/s<o:p
class=""></o:p></span></div>
<div style="margin: 0cm 0cm 0.0001pt; font-size: 10pt;
font-family: Calibri, sans-serif;" class=""><span
style="font-size: 10.5pt; font-family: Helvetica;"
class="">em_unit optional, expressing the unit
encoded in the cube for the spectral axis<o:p
class=""></o:p></span></div>
<div style="margin: 0cm 0cm 0.0001pt; font-size: 10pt;
font-family: Calibri, sans-serif;" class=""><span
style="font-size: 10.5pt; font-family: Helvetica;"
class="">em_resolution optional, expressing the
resolution in the units used by the data cube<o:p
class=""></o:p></span></div>
<div style="margin: 0cm 0cm 0.0001pt; font-size: 10pt;
font-family: Calibri, sans-serif;" class=""><span
style="font-size: 10.5pt; font-family: Helvetica;"
class=""><o:p class=""> </o:p></span></div>
<div style="margin: 0cm 0cm 0.0001pt; font-size: 10pt;
font-family: Calibri, sans-serif;" class=""><span
style="font-size: 10.5pt; font-family: Helvetica;"
class="">If we converge on this, I could put
together a little document with a detailed
proposal.<o:p class=""></o:p></span></div>
<div style="margin: 0cm 0cm 0.0001pt; font-size: 10pt;
font-family: Calibri, sans-serif;" class=""><span
style="font-size: 10.5pt; font-family: Helvetica;"
class="">Would that considered useful?<o:p
class=""></o:p></span></div>
<div style="margin: 0cm 0cm 0.0001pt; font-size: 10pt;
font-family: Calibri, sans-serif;" class=""><span
style="font-size: 10.5pt; font-family: Helvetica;"
class=""><o:p class=""> </o:p></span></div>
<div style="margin: 0cm 0cm 0.0001pt; font-size: 10pt;
font-family: Calibri, sans-serif;" class=""><span
style="font-size: 10.5pt; font-family: Helvetica;"
class="">Cheers,<o:p class=""></o:p></span></div>
<div style="margin: 0cm 0cm 0.0001pt; font-size: 10pt;
font-family: Calibri, sans-serif;" class=""><span
style="font-size: 10.5pt; font-family: Helvetica;"
class="">Alberto<o:p class=""></o:p></span></div>
<div style="margin: 0cm 0cm 0.0001pt; font-size: 10pt;
font-family: Calibri, sans-serif;" class=""><span
style="font-size: 10.5pt; font-family: Helvetica;"
class=""><o:p class=""> </o:p></span></div>
<div style="margin: 0cm 0cm 0.0001pt; font-size: 10pt;
font-family: Calibri, sans-serif;" class=""><span
style="font-size: 10.5pt; font-family: Helvetica;"
class="">(*) cross-standard issue: the
spect.dopplerVeloc.rel is mentioned in the ObsCore
standard, <o:p class=""></o:p></span></div>
<div style="margin: 0cm 0cm 0.0001pt; font-size: 10pt;
font-family: Calibri, sans-serif;" class=""><span
style="font-size: 10.5pt; font-family: Helvetica;"
class="">but it is not a recognised value in the
current UCD1+ standard.<o:p class=""></o:p></span></div>
<div style="margin: 0cm 0cm 0.0001pt; font-size: 10pt;
font-family: Calibri, sans-serif;" class=""><span
style="font-size: 10.5pt; font-family: Helvetica;"
class="">We will need to act on this (Mireille?).<o:p
class=""></o:p></span></div>
<div style="margin: 0cm 0cm 0.0001pt; font-size: 10pt;
font-family: Calibri, sans-serif;" class=""><span
style="font-size: 11pt;" class=""><o:p class=""> </o:p></span></div>
<div style="border-style: solid none none;
border-top-width: 1pt; border-top-color: rgb(181,
196, 223); padding: 3pt 0cm 0cm;" class="">
<div style="margin: 0cm 0cm 0.0001pt; font-size:
10pt; font-family: Calibri, sans-serif;" class=""><b
class=""><span style="font-size: 12pt;" class="">From:<span
class="Apple-converted-space"> </span></span></b><span
style="font-size: 12pt;" class="">"Dempsey,
James (IM&T, Black Mountain)" <<a
href="mailto:James.Dempsey@csiro.au"
style="color: purple; text-decoration:
underline;" class="moz-txt-link-freetext"
moz-do-not-send="true">James.Dempsey@csiro.au</a>><br
class="">
<b class="">Date:<span
class="Apple-converted-space"> </span></b>Thursday,
16 February 2023 at 00:21<br class="">
<b class="">To:<span
class="Apple-converted-space"> </span></b>Alberto
Micol <<a href="mailto:amicol@eso.org"
style="color: purple; text-decoration:
underline;" class="moz-txt-link-freetext"
moz-do-not-send="true">amicol@eso.org</a>>,
"<a href="mailto:dal@ivoa.net" style="color:
purple; text-decoration: underline;"
class="moz-txt-link-freetext"
moz-do-not-send="true">dal@ivoa.net</a>" <<a
href="mailto:dal@ivoa.net" style="color:
purple; text-decoration: underline;"
class="moz-txt-link-freetext"
moz-do-not-send="true">dal@ivoa.net</a>><br
class="">
<b class="">Subject:<span
class="Apple-converted-space"> </span></b>Re:
ObsCore for velocity cubes<o:p class=""></o:p></span></div>
</div>
<div class="">
<div style="margin: 0cm 0cm 0.0001pt; font-size:
10pt; font-family: Calibri, sans-serif;" class=""><span
style="font-size: 11pt;" class=""><o:p class=""> </o:p></span></div>
</div>
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<div style="margin: 0cm 0cm 0.0001pt;
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class="">This email was sent from outside
of ESO from the address<strong class=""><span
style="font-family: Arial,
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href="mailto:prvs=40330730a=James.Dempsey@csiro.au"
style="color: purple;
text-decoration: underline;"
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style="color: purple; text-decoration:
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<div style="margin: 0cm 0cm 0.0001pt; font-size: 10pt;
font-family: Calibri, sans-serif;" class=""><span
style="font-size: 11pt; color: white;" class="">Hi
Alberto</span><span style="font-size: 11pt;"
class="">,</span><o:p class=""></o:p></div>
<div style="margin: 0cm 0cm 0.0001pt; font-size: 10pt;
font-family: Calibri, sans-serif;" class=""><span
style="font-size: 11pt;" class=""> </span><o:p
class=""></o:p></div>
<div style="margin: 0cm 0cm 0.0001pt; font-size: 10pt;
font-family: Calibri, sans-serif;" class=""><span
style="font-size: 11pt;" class="">At CASDA we
support cutouts of velocity spectral line cubes.</span><o:p
class=""></o:p></div>
<div style="margin: 0cm 0cm 0.0001pt; font-size: 10pt;
font-family: Calibri, sans-serif;" class=""><span
style="font-size: 11pt;" class=""> </span><o:p
class=""></o:p></div>
<div style="margin: 0cm 0cm 0.0001pt; font-size: 10pt;
font-family: Calibri, sans-serif;" class=""><span
style="font-size: 11pt;" class="">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!</span><o:p
class=""></o:p></div>
<div style="margin: 0cm 0cm 0.0001pt; font-size: 10pt;
font-family: Calibri, sans-serif;" class=""><span
style="font-size: 11pt;" class=""> </span><o:p
class=""></o:p></div>
<div style="margin: 0cm 0cm 0.0001pt; font-size: 10pt;
font-family: Calibri, sans-serif;" class=""><span
style="font-size: 11pt;" class="">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).</span><o:p
class=""></o:p></div>
<ul style="margin-bottom: 0cm; margin-top: 0cm;"
class="" type="disc">
<li class="MsoListParagraph" style="margin: 0cm 0cm
0.0001pt; font-size: 10pt; font-family: Calibri,
sans-serif;"><span style="font-size: 11pt;"
class="">v_resolution – value of CDELT3 or
CDELT4</span><o:p class=""></o:p></li>
<li class="MsoListParagraph" style="margin: 0cm 0cm
0.0001pt; font-size: 10pt; font-family: Calibri,
sans-serif;"><span style="font-size: 11pt;"
class="">v_unit – although this should always be
m/s</span><o:p class=""></o:p></li>
</ul>
<div style="margin: 0cm 0cm 0.0001pt; font-size: 10pt;
font-family: Calibri, sans-serif;" class=""><span
style="font-size: 11pt;" class=""> </span><o:p
class=""></o:p></div>
<div style="margin: 0cm 0cm 0.0001pt; font-size: 10pt;
font-family: Calibri, sans-serif;" class=""><span
style="font-size: 11pt;" class="">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.</span><o:p class=""></o:p></div>
<div style="margin: 0cm 0cm 0.0001pt; font-size: 10pt;
font-family: Calibri, sans-serif;" class=""><span
style="font-size: 11pt;" class=""> </span><o:p
class=""></o:p></div>
<div class="">
<div class="">
<div style="margin: 0cm 0cm 0.0001pt; font-size:
10pt; font-family: Calibri, sans-serif;"
class=""><span style="font-size: 11pt;" class="">Cheers,</span><o:p
class=""></o:p></div>
<div style="margin: 0cm 0cm 0.0001pt; font-size:
10pt; font-family: Calibri, sans-serif;"
class=""><b class=""><span style="font-size:
11pt; color: rgb(0, 169, 206);" class="">James
Dempsey</span></b><o:p class=""></o:p></div>
<div style="margin: 0cm 0cm 0.0001pt; font-size:
10pt; font-family: Calibri, sans-serif;"
class=""><span style="font-size: 9pt;" class="">Senior
Developer <span class="Apple-converted-space"> </span></span><span
style="font-size: 9pt; color: rgb(0, 169,
206);" class="">|</span><span
style="font-size: 9pt;" class=""> CSIRO </span><o:p
class=""></o:p></div>
<div style="margin: 0cm 0cm 0.0001pt; font-size:
10pt; font-family: Calibri, sans-serif;"
class=""><span style="font-size: 11pt;" class=""><a
href="mailto:james.dempsey@csiro.au"
style="color: purple; text-decoration:
underline;" class="" moz-do-not-send="true"><span
style="font-size: 9pt; color: rgb(5, 99,
193);" class="">james.dempsey@csiro.au</span></a></span><span
style="font-size: 9pt;" class=""> <span
class="Apple-converted-space"> </span></span><span
style="font-size: 9pt; color: rgb(0, 169,
206);" class="">|</span><span
style="font-size: 9pt;" class=""> 02 6214
2912</span><o:p class=""></o:p></div>
</div>
</div>
<div style="margin: 0cm 0cm 0.0001pt; font-size: 10pt;
font-family: Calibri, sans-serif;" class=""><span
style="font-size: 11pt;" class=""> </span><o:p
class=""></o:p></div>
<div style="margin: 0cm 0cm 0.0001pt; font-size: 10pt;
font-family: Calibri, sans-serif;" class=""><span
style="font-size: 11pt;" class=""> </span><o:p
class=""></o:p></div>
<div style="border-style: solid none none;
border-top-width: 1pt; border-top-color: rgb(181,
196, 223); padding: 3pt 0cm 0cm;" class="">
<p class="MsoNormal" style="margin: 0cm 0cm 12pt;
font-size: 10pt; font-family: Calibri,
sans-serif;"><b class=""><span style="font-size:
12pt;" class="">From:<span
class="Apple-converted-space"> </span></span></b><span
style="font-size: 12pt;" class="">dal <<a
href="mailto:dal-bounces@ivoa.net"
class="moz-txt-link-freetext"
moz-do-not-send="true">dal-bounces@ivoa.net</a>>
on behalf of alberto micol <<a
href="mailto:amicol.ivoa@googlemail.com"
class="moz-txt-link-freetext"
moz-do-not-send="true">amicol.ivoa@googlemail.com</a>><br
class="">
<b class="">Date:<span
class="Apple-converted-space"> </span></b>Thursday,
16 February 2023 at 12:02 am<br class="">
<b class="">To:<span
class="Apple-converted-space"> </span></b><a
href="mailto:dal@ivoa.net"
class="moz-txt-link-freetext"
moz-do-not-send="true">dal@ivoa.net</a> <<a
href="mailto:dal@ivoa.net"
class="moz-txt-link-freetext"
moz-do-not-send="true">dal@ivoa.net</a>><br
class="">
<b class="">Subject:<span
class="Apple-converted-space"> </span></b>ObsCore
for velocity cubes</span><o:p class=""></o:p></p>
</div>
<div style="margin: 0cm 0cm 0.0001pt; font-size: 10pt;
font-family: Calibri, sans-serif;" class=""><span
style="font-size: 11pt;" class="">Dear ObsCorers,</span><o:p
class=""></o:p></div>
<div class="">
<div style="margin: 0cm 0cm 0.0001pt; font-size:
10pt; font-family: Calibri, sans-serif;" class=""><span
style="font-size: 11pt;" class=""> </span><o:p
class=""></o:p></div>
</div>
<div class="">
<div style="margin: 0cm 0cm 0.0001pt; font-size:
10pt; font-family: Calibri, sans-serif;" class=""><span
style="font-size: 11pt;" class="">I have
received with much interest the ObsCore
extension for RADIO data, thanks for that very
clear document.</span><o:p class=""></o:p></div>
</div>
<div class="">
<div style="margin: 0cm 0cm 0.0001pt; font-size:
10pt; font-family: Calibri, sans-serif;" class=""><span
style="font-size: 11pt;" class=""> </span><o:p
class=""></o:p></div>
</div>
<div class="">
<div style="margin: 0cm 0cm 0.0001pt; font-size:
10pt; font-family: Calibri, sans-serif;" class=""><span
style="font-size: 11pt;" class="">Would it be
possible to have a similar extension for cubes
with velocity as third axis (the other two being
the usual spatial ones)?</span><o:p class=""></o:p></div>
</div>
<div class="">
<div style="margin: 0cm 0cm 0.0001pt; font-size:
10pt; font-family: Calibri, sans-serif;" class=""><span
style="font-size: 11pt;" class="">Let me call
them “velocity cubes”...</span><o:p class=""></o:p></div>
</div>
<div class="">
<div style="margin: 0cm 0cm 0.0001pt; font-size:
10pt; font-family: Calibri, sans-serif;" class=""><span
style="font-size: 11pt;" class=""> </span><o:p
class=""></o:p></div>
</div>
<div class="">
<div style="margin: 0cm 0cm 0.0001pt; font-size:
10pt; font-family: Calibri, sans-serif;" class=""><span
style="font-size: 11pt;" class="">Here my use
case…</span><o:p class=""></o:p></div>
</div>
<div class="">
<div style="margin: 0cm 0cm 0.0001pt; font-size:
10pt; font-family: Calibri, sans-serif;" class=""><span
style="font-size: 11pt;" class=""> </span><o:p
class=""></o:p></div>
</div>
<div class="">
<div style="margin: 0cm 0cm 0.0001pt; font-size:
10pt; font-family: Calibri, sans-serif;" class=""><span
style="font-size: 11pt;" class="">At ESO we need
to support cutouts of velocity cubes.</span><o:p
class=""></o:p></div>
</div>
<div class="">
<div style="margin: 0cm 0cm 0.0001pt; font-size:
10pt; font-family: Calibri, sans-serif;" class=""><span
style="font-size: 11pt;" class=""> </span><o:p
class=""></o:p></div>
</div>
<div class="">
<div style="margin: 0cm 0cm 0.0001pt; font-size:
10pt; font-family: Calibri, sans-serif;" class=""><span
style="font-size: 11pt;" class="">Up to now our
SODA interface supported spectra, images, and
wavelength cubes;</span><o:p class=""></o:p></div>
</div>
<div class="">
<div style="margin: 0cm 0cm 0.0001pt; font-size:
10pt; font-family: Calibri, sans-serif;" class=""><span
style="font-size: 11pt;" class="">to provide the
user with the SODA input parameters and their
possible MIN/MAX values</span><o:p class=""></o:p></div>
</div>
<div class="">
<div style="margin: 0cm 0cm 0.0001pt; font-size:
10pt; font-family: Calibri, sans-serif;" class=""><span
style="font-size: 11pt;" class="">we query
ivoa.ObsCore.</span><o:p class=""></o:p></div>
</div>
<div class="">
<div style="margin: 0cm 0cm 0.0001pt; font-size:
10pt; font-family: Calibri, sans-serif;" class=""><span
style="font-size: 11pt;" class=""> </span><o:p
class=""></o:p></div>
</div>
<div class="">
<div style="margin: 0cm 0cm 0.0001pt; font-size:
10pt; font-family: Calibri, sans-serif;" class=""><span
style="font-size: 11pt;" class="">Now with the
introduction of velocity cubes, we would like to
get the necessary SODA input params also from
ObsCore.</span><o:p class=""></o:p></div>
</div>
<div class="">
<div style="margin: 0cm 0cm 0.0001pt; font-size:
10pt; font-family: Calibri, sans-serif;" class=""><span
style="font-size: 11pt;" class="">We can
certainly do so by extending our own ObsCore
table (ObsCore allows to extend the table), but
I was wondering</span><o:p class=""></o:p></div>
</div>
<div class="">
<div style="margin: 0cm 0cm 0.0001pt; font-size:
10pt; font-family: Calibri, sans-serif;" class=""><span
style="font-size: 11pt;" class="">if others have
similar needs, and see if we can agree with a
common ObsCore extension.</span><o:p class=""></o:p></div>
</div>
<div class="">
<div style="margin: 0cm 0cm 0.0001pt; font-size:
10pt; font-family: Calibri, sans-serif;" class=""><span
style="font-size: 11pt;" class=""> </span><o:p
class=""></o:p></div>
</div>
<div class="">
<div style="margin: 0cm 0cm 0.0001pt; font-size:
10pt; font-family: Calibri, sans-serif;" class=""><span
style="font-size: 11pt;" class="">Velocity cubes
should come in a FITS format as described by
Greisen et al, 2006, so-called Paper 3.</span><o:p
class=""></o:p></div>
</div>
<blockquote style="margin: 5pt 0cm 5pt 30pt;" class=""
type="cite">
<div class="">
<div style="margin: 0cm 0cm 0.0001pt; font-size:
10pt; font-family: Calibri, sans-serif;"
class=""><span style="font-size: 11pt;" class="">Shortly
summarised, the velocity can be either:</span><o:p
class=""></o:p></div>
</div>
</blockquote>
<div class="">
<ul style="margin-bottom: 0cm;" class="" type="disc">
<ul style="margin-bottom: 0cm;" class=""
type="circle">
<li class="MsoNormal" style="margin: 0cm 0cm
0.0001pt; font-size: 10pt; font-family:
Calibri, sans-serif;"><span style="font-size:
11pt;" class="">a radio (VRAD), </span><o:p
class=""></o:p></li>
<li class="MsoNormal" style="margin: 0cm 0cm
0.0001pt; font-size: 10pt; font-family:
Calibri, sans-serif;"><span style="font-size:
11pt;" class="">an optical (VOPT), </span><o:p
class=""></o:p></li>
<li class="MsoNormal" style="margin: 0cm 0cm
0.0001pt; font-size: 10pt; font-family:
Calibri, sans-serif;"><span style="font-size:
11pt;" class="">a relativistic velocity
(ZOPT), </span><o:p class=""></o:p></li>
<li class="MsoNormal" style="margin: 0cm 0cm
0.0001pt; font-size: 10pt; font-family:
Calibri, sans-serif;"><span style="font-size:
11pt;" class="">a generic apparent velocity
(VELO).</span><o:p class=""></o:p></li>
</ul>
</ul>
</div>
<blockquote style="margin: 5pt 0cm 5pt 30pt;" class=""
type="cite">
<div class="">
<div style="margin: 0cm 0cm 0.0001pt; font-size:
10pt; font-family: Calibri, sans-serif;"
class=""><span style="font-size: 11pt;" class="">The
RESTFRQa (RESTWAVa) keyword conveys the
necessary reference frequency (wavelength) to
transform velocity into frequency or
wavelength. </span><o:p class=""></o:p></div>
</div>
<div class="">
<div style="margin: 0cm 0cm 0.0001pt; font-size:
10pt; font-family: Calibri, sans-serif;"
class=""><span style="font-size: 11pt;" class="">The
velocity unit is m/s.</span><o:p class=""></o:p></div>
</div>
</blockquote>
<div class="">
<div style="margin: 0cm 0cm 0.0001pt; font-size:
10pt; font-family: Calibri, sans-serif;" class=""><span
style="font-size: 11pt;" class=""> </span><o:p
class=""></o:p></div>
</div>
<div class="">
<div style="margin: 0cm 0cm 0.0001pt; font-size:
10pt; font-family: Calibri, sans-serif;" class=""><span
style="font-size: 11pt;" class="">SODA cutouts
on the velocity axis are usually formulated by
passing cuts already expressed in velocity</span><o:p
class=""></o:p></div>
</div>
<div class="">
<div style="margin: 0cm 0cm 0.0001pt; font-size:
10pt; font-family: Calibri, sans-serif;" class=""><span
style="font-size: 11pt;" class="">though it must
be possible to perform the conversions to and
from frequency/wavelength.</span><o:p class=""></o:p></div>
</div>
<div class="">
<div style="margin: 0cm 0cm 0.0001pt; font-size:
10pt; font-family: Calibri, sans-serif;" class=""><span
style="font-size: 11pt;" class=""> </span><o:p
class=""></o:p></div>
</div>
<div class="">
<div style="margin: 0cm 0cm 0.0001pt; font-size:
10pt; font-family: Calibri, sans-serif;" class=""><span
style="font-size: 11pt;" class="">What would
then be needed in ObsCore is:</span><o:p
class=""></o:p></div>
</div>
<div class="">
<div style="margin: 0cm 0cm 0.0001pt; font-size:
10pt; font-family: Calibri, sans-serif;" class=""><span
style="font-size: 11pt;" class=""> </span><o:p
class=""></o:p></div>
</div>
<div class="">
<div style="margin: 0cm 0cm 0.0001pt; font-size:
10pt; font-family: Calibri, sans-serif;" class=""><span
style="font-size: 11pt;" class="">v_min</span><o:p
class=""></o:p></div>
</div>
<div class="">
<div style="margin: 0cm 0cm 0.0001pt; font-size:
10pt; font-family: Calibri, sans-serif;" class=""><span
style="font-size: 11pt;" class="">v_max</span><o:p
class=""></o:p></div>
</div>
<div class="">
<div style="margin: 0cm 0cm 0.0001pt; font-size:
10pt; font-family: Calibri, sans-serif;" class=""><span
style="font-size: 11pt;" class=""> </span><o:p
class=""></o:p></div>
</div>
<div class="">
<div style="margin: 0cm 0cm 0.0001pt; font-size:
10pt; font-family: Calibri, sans-serif;" class=""><span
style="font-size: 11pt;" class="">but also, in
case of radio velocity cube:</span><o:p class=""></o:p></div>
</div>
<div class="">
<div style="margin: 0cm 0cm 0.0001pt; font-size:
10pt; font-family: Calibri, sans-serif;" class=""><span
style="font-size: 11pt;" class="">f_min</span><o:p
class=""></o:p></div>
</div>
<div class="">
<div style="margin: 0cm 0cm 0.0001pt; font-size:
10pt; font-family: Calibri, sans-serif;" class=""><span
style="font-size: 11pt;" class="">f_max (getting
these from the RADIO extension)</span><o:p
class=""></o:p></div>
</div>
<div class="">
<div style="margin: 0cm 0cm 0.0001pt; font-size:
10pt; font-family: Calibri, sans-serif;" class=""><span
style="font-size: 11pt;" class="">f_rest =
RESTFRQ</span><o:p class=""></o:p></div>
</div>
<div class="">
<div style="margin: 0cm 0cm 0.0001pt; font-size:
10pt; font-family: Calibri, sans-serif;" class=""><span
style="font-size: 11pt;" class=""> </span><o:p
class=""></o:p></div>
</div>
<div class="">
<div style="margin: 0cm 0cm 0.0001pt; font-size:
10pt; font-family: Calibri, sans-serif;" class=""><span
style="font-size: 11pt;" class="">and, in case
of a optical or relativistic velocity cube</span><o:p
class=""></o:p></div>
</div>
<div class="">
<div style="margin: 0cm 0cm 0.0001pt; font-size:
10pt; font-family: Calibri, sans-serif;" class=""><span
style="font-size: 11pt;" class="">em_rest =
RESTWAV</span><o:p class=""></o:p></div>
</div>
<div class="">
<div style="margin: 0cm 0cm 0.0001pt; font-size:
10pt; font-family: Calibri, sans-serif;" class=""><span
style="font-size: 11pt;" class="">(we already
have em_min, em_max)</span><o:p class=""></o:p></div>
</div>
<div class="">
<div style="margin: 0cm 0cm 0.0001pt; font-size:
10pt; font-family: Calibri, sans-serif;" class=""><span
style="font-size: 11pt;" class=""> </span><o:p
class=""></o:p></div>
</div>
<div class="">
<div style="margin: 0cm 0cm 0.0001pt; font-size:
10pt; font-family: Calibri, sans-serif;" class=""><span
style="font-size: 11pt;" class="">The
em_resolv_power should then be set to:</span><o:p
class=""></o:p></div>
</div>
<div class="">
<div style="margin: 0cm 0cm 0.0001pt; font-size:
10pt; font-family: Calibri, sans-serif;" class=""><span
style="font-size: 11pt;" class=""> lambda
freq c</span><o:p
class=""></o:p></div>
</div>
<div class="">
<div style="margin: 0cm 0cm 0.0001pt; font-size:
10pt; font-family: Calibri, sans-serif;" class=""><span
style="font-size: 11pt;" class=""> ——————— =
————— = —————</span><o:p class=""></o:p></div>
</div>
<div class="">
<div style="margin: 0cm 0cm 0.0001pt; font-size:
10pt; font-family: Calibri, sans-serif;" class=""><span
style="font-size: 11pt;" class=""> delta lambda
delta freq 2 * delta_v</span><o:p
class=""></o:p></div>
</div>
<div class="">
<div style="margin: 0cm 0cm 0.0001pt; font-size:
10pt; font-family: Calibri, sans-serif;" class=""><span
style="font-size: 11pt;" class=""> </span><o:p
class=""></o:p></div>
</div>
<div class="">
<div style="margin: 0cm 0cm 0.0001pt; font-size:
10pt; font-family: Calibri, sans-serif;" class=""><span
style="font-size: 11pt;" class="">where delta_v
is the CD3_3 in the cube (in the example of a
cube with the velocity on the third axis);</span><o:p
class=""></o:p></div>
</div>
<div class="">
<div style="margin: 0cm 0cm 0.0001pt; font-size:
10pt; font-family: Calibri, sans-serif;" class=""><span
style="font-size: 11pt;" class="">but I would
also likely accept a v_pixel_scale (= delta_v).</span><o:p
class=""></o:p></div>
</div>
<div class="">
<div style="margin: 0cm 0cm 0.0001pt; font-size:
10pt; font-family: Calibri, sans-serif;" class=""><span
style="font-size: 11pt;" class=""> </span><o:p
class=""></o:p></div>
</div>
<div class="">
<div style="margin: 0cm 0cm 0.0001pt; font-size:
10pt; font-family: Calibri, sans-serif;" class=""><span
style="font-size: 11pt;" class="">The UCD for
the velocity should then be:</span><o:p class=""></o:p></div>
</div>
<div class="">
<pre style="margin: 0cm 0cm 0.0001pt; font-size: 10pt; font-family: 'Courier New';" class="">spect.dopplerVeloc.opt<o:p class=""></o:p></pre>
<div class="">
<pre style="margin: 0cm 0cm 0.0001pt; font-size: 10pt; font-family: 'Courier New';" class="">spect.dopplerVeloc.radio<o:p class=""></o:p></pre>
<div class="">
<div style="margin: 0cm 0cm 0.0001pt; font-size:
10pt; font-family: Calibri, sans-serif;"
class=""><span style="font-size: 11pt;"
class="">unsure what it should be for the
relativistic case.</span><o:p class=""></o:p></div>
</div>
</div>
</div>
<div class="">
<div style="margin: 0cm 0cm 0.0001pt; font-size:
10pt; font-family: Calibri, sans-serif;" class=""><span
style="font-size: 11pt;" class=""> </span><o:p
class=""></o:p></div>
</div>
<div class="">
<div style="margin: 0cm 0cm 0.0001pt; font-size:
10pt; font-family: Calibri, sans-serif;" class=""><span
style="font-size: 11pt;" class="">This would
allow us at ESO to implement SODA on top of
ObsCore (as already done for all other
parameters)</span><o:p class=""></o:p></div>
</div>
<div class="">
<div style="margin: 0cm 0cm 0.0001pt; font-size:
10pt; font-family: Calibri, sans-serif;" class=""><span
style="font-size: 11pt;" class="">and would
allow astronomer to search the velocity cubes
with certain characteristics using ObsCore.</span><o:p
class=""></o:p></div>
</div>
<div class="">
<div style="margin: 0cm 0cm 0.0001pt; font-size:
10pt; font-family: Calibri, sans-serif;" class=""><span
style="font-size: 11pt;" class=""> </span><o:p
class=""></o:p></div>
</div>
<div class="">
<div style="margin: 0cm 0cm 0.0001pt; font-size:
10pt; font-family: Calibri, sans-serif;" class=""><span
style="font-size: 11pt;" class="">What do you
think? </span><o:p class=""></o:p></div>
</div>
<div class="">
<div style="margin: 0cm 0cm 0.0001pt; font-size:
10pt; font-family: Calibri, sans-serif;" class=""><span
style="font-size: 11pt;" class="">Is that
doable? I think at ESO we will simply start
implementing the above extra ObsCore parameters
(unless you suggest different names for that),</span><o:p
class=""></o:p></div>
</div>
<div class="">
<div style="margin: 0cm 0cm 0.0001pt; font-size:
10pt; font-family: Calibri, sans-serif;" class=""><span
style="font-size: 11pt;" class="">while waiting
to see if there is more interest to build a
proper standard.</span><o:p class=""></o:p></div>
</div>
<div class="">
<div style="margin: 0cm 0cm 0.0001pt; font-size:
10pt; font-family: Calibri, sans-serif;" class=""><span
style="font-size: 11pt;" class=""> </span><o:p
class=""></o:p></div>
</div>
<div class="">
<div style="margin: 0cm 0cm 0.0001pt; font-size:
10pt; font-family: Calibri, sans-serif;" class=""><span
style="font-size: 11pt;" class="">Eager to know
what you think, </span><o:p class=""></o:p></div>
</div>
<div class="">
<div style="margin: 0cm 0cm 0.0001pt; font-size:
10pt; font-family: Calibri, sans-serif;" class=""><span
style="font-size: 11pt;" class="">Cheers,</span><o:p
class=""></o:p></div>
</div>
<div class="">
<div style="margin: 0cm 0cm 0.0001pt; font-size:
10pt; font-family: Calibri, sans-serif;" class=""><span
style="font-size: 11pt;" class="">Alberto</span></div>
</div>
</div>
</div>
</blockquote>
</div>
<br class="">
</div>
</div>
</blockquote>
<p><br>
</p>
</body>
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