A Proposal for a TIMESYS Element in VOTable

[AdaNebot]

Hi, Tom, Arnold, 

I agree that saying UNKOWN seems to be unfair. The term TOPOCENTER can be referred to the location of the instrument as Arnold mentions. 
Perhaps the best way to avoid any possible ambiguity is to write some more examples in the document and explicitly mention that TOPOCENTER includes position of satellites too. 
Including ephemerides on the other hand, and in my opinion, would be complicating things for this simple annotation. 

We are taking into account the comments we are receiving and I propose to move the discussion to Apps for the more technical details. 

Cheers,
Ada

> On 1 Nov 2018, at 20:20, Arnold Rots <arots at cfa.harvard.edu> wrote:
> 
> The term TOPOCENTER has been used for several decades now to indicate the location where the time is actually measured, i.e., at the detector/telescope/observatory, regardless of whether the instrument is located on the earth's surface or in space (or wherever else).
> In both cases information is needed that specifies where that location is, whether it is expressed as a fixed location wrt to the GEOCENTER (in any type of spatial coordinate system) or as an (orbit) ephemeris.
> 
> Cheers,
> 
>   - Arnold
> 
> -------------------------------------------------------------------------------------------------------------
> Arnold H. Rots                                          Chandra X-ray Science Center
> Smithsonian Astrophysical Observatory                   tel:  +1 617 496 7701
> 60 Garden Street, MS 67                                      fax:  +1 617 495 7356
> Cambridge, MA 02138                                         arots at cfa.harvard.edu <mailto:arots at cfa.harvard.edu>
> USA                                                   http://hea-www.harvard.edu/~arots/ <http://hea-www.harvard.edu/~arots/>
> --------------------------------------------------------------------------------------------------------------
> 
> 
> 
> On Wed, Oct 31, 2018 at 3:55 PM Tom McGlynn <tom.mcglynn at nasa.gov <mailto:tom.mcglynn at nasa.gov>> wrote:
> It seems to me that this makes no accommodation for satellites where the 
> reference position is variable but not
> unknown.  The definition of topocentric is according to my dictionary: 
> "**relating to, measured from, or as if observed from a particular point 
> on the earth's surface *: *having or relating to such a point as origin" 
> so TOPOCENTER is fine for earth based observations (though there are 
> balloons that move quite a bit during an observation campaign) but it 
> would be a stretch to use it for satellites.  I wouldn't want to say 
> UNKNOWN though.    Maybe SATELLITE or VARIABLE? Lots of HEASARC data 
> have times that are measured at the satellite -- and that includes lots 
> of the GRB detecting satellites for which this kind of feature would be 
> very nice.
> 
>      Tom McG.
> 
> AdaNebot wrote:
> > Dear All,
> >
> > A Note entitled “*A Proposal for a TIMESYS Element in VOTable*” can be 
> > found under:
> >
> > http://ivoa.net/documents/Notes/TimeSys/ <http://ivoa.net/documents/Notes/TimeSys/>
> >
> >
> > Thanks for taking the time to read this document,
> >
> > Happy reading!
> >
> > See you in College Park,
> > Ada Nebot
> > TDIG Chair
> >
> 

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mail.ivoa.net/pipermail/apps/attachments/20181105/4da2737f/attachment.html>