Re: Draft list of ucd-words

From: Pierre Didelon <pdidelon-at-cea.fr>
Date: Tue, 28 Jun 2005 15:16:26 +0200


Hi everybody,
some comments...

  1. global comments

A.0 instr.obsty

- S | instr.obsty                  |  Observatory satellite mission
you mean Observatory or satellite mission -> Observatory / satellite mission  ?
- Q | instr.obsty.site.seeing      |  Seeing 

Is this the global seeing resulting of detector, instrument, atmosphere... or does it concern only the instrumental part? If so, did we need a obs.seeing?

Not clear for me.

A.1 phys.veloc.trans
- Q | phys.veloc.transverse | Transverse / tangential velocity I am not sure that these two definitions are (allways?) compatible. Moreover, transverse is perhaps not the right word. It isn't tangential, as opposed to radial? Or do we need two definitions? But velocity transverse to the mouvment seems strange/unappropriate?

A.2 radial velocities
they are now spread in 3 separate group

- phys.veloc.[lg|lsr]
- spect.dopplerVeloc.*
- src.redshift.*

Is spect.dopplerVeloc.* equivalent to radial velocity? Some "reduced" RV, to the earth center, to the sun are not defined/available, ( see gc, geoc and hc in src.veloc.radial at http://www.imcce.fr/fr/expert/ssvo/wgovp/ucdtree.html ) and the frame corresponding to spect.dopplerVeloc is not defined. So, phys.veloc.hc for heliocentric value is not available, while the corresponding position pos.heliocentric is. I suggest to complete RV and clearly identify them using phys.veloc.radial.[gc|geoc|hc|lg|lsr] and to change description of spect.dopplerVeloc.* to clearly define the information about the "place of measurement" : ObsLocation (in case of spacecraft it can be tricky) or referential frame.

A.3 pos.* the big case/issue already clarified but still some inhomogeneity or confusion (at least in my head).

A.3.1 pos.earth

  Q | pos.earth.lon                |  Longitude on Earth
exists but not latitude!
Q | pos.earth.altitude           |  Altitude on Earth
exists but not distance which give the distance to the center

A.3.2 lon/lat/alt/dist
For any coordinate system (pos.*centric and mainly pos.bodyrc) the four informations can be usefull, and if pos.distance

                      is available the others don't exist, and can be used to construct composed words.
I suggest introduction of pos.[alt|lat|lon] (at least the two last ones) to be able to used composed words like pos.lat;pos.bodyrc or to introduce [dist|lat|lon] for all coordinate system and alt for some of them.

A.3.3 Some subdivision are not sufficients. pos.bodyrc as mentionned above ;-)
but also : pos.precess, pos.earthop.nutation and pos.earthop too see corresponding needs at http://www.imcce.fr/fr/expert/ssvo/wgovp/ucdtree.html

B additional comments mainly related to (small?) solar system objects ( or extra solar system sytem and not only planetary one ;-) )

B.1 Mean motion

 >>>>> Andrea Preite Martinez wrote:
 >>>>>
 >>>>>> 12. src.orbital.meanMotion
 >>>>>> I suppose it is an average angular velocity (src.veloc.ang;stat.mean).
 >>>>>> No strong feelings about it.
 >>>>>

No, the mean motion is not an average angular velocity. It is given by the third Kepler's law: n2 * a3 = cste with n the mean motion and a the semi-major axis of the orbit. So it is a corner stone of the computation of orbits: we need it as a proper UCD.

B.2 asteroid Absolute Magnitude

H is the absolute magnitude which already exist in the UCD (phys.magAbs) for asteroids we need also the slope parameter usually called G : phys.magAbs.G but seen as a kind of "calibration" parameter may be a better place somewhere else in the UCD tree is perhaps possible?

B.3 pos.precess

I guess pos.precess could be more generic because it could be used both for the equatorial and ecliptic precessions. Perhaps we should change .ra and .dec to .lon and .lat and, in the same way, .dzeta, .z and ,theta should be change because they usually refer to the equatorial precession when the ecliptic precession parameters are expressed with other letters.

B.4 pos.eop.*

Jonathan McDowell wrote:
 > * pos.eop.* I like, although as we become more active on other worlds isn't it likely  > that we'll be needing similar parameters for Mars, etc.? But maybe it's fine for now.

  yes, SolarSystem people mind about this. But the Earth is a special case which is used often in ephemeris computation. I guess that first this UCD should be created and then a more generic one should be added ?

That's all for the moment.
sincerely yours,
Pierre

Andrea Preite Martinez wrote:

> Dear all,
>
> after 26 days of discussion and contributions from many of you, I decided to
> sum up things and to modify the list of words according to my personal
> feelings.
>
> You can find the proposed list in the txt file appended.
> Of course the discussion is not over, but unfortunately we need a rather
> "stable" version soon.
> The PR-version of the document (the text accompanying the list) will be sent
> around after the meeting in Garching.

...
>
> Regards
>
> Andrea
> ==============================================================================
> Andrea Preite Martinez andrea-at-rm.iasf.cnr.it
> Istituto di Astrofisica Spaziale Tel.:+39.06.4993.4641
> Area di Ricerca di Tor Vergata Fax.:+39.06.2066.0188
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DIDELON :@: pdidelon_at_cea.fr Phone : 33 (0)1 69 08 58 89 CEA SACLAY - Service d'Astrophysique 91191 Gif-Sur-Yvette Cedex
Received on 2005-06-28Z15:17:02