A Proposal for a TIMESYS Element in VOTable

[Baptiste Cecconi]

This issue of UNKNOWN versus TOPOCENTER (versus SATELLITE versus VARIABLE) is also very important for Solar System use cases, with the many space exploration missions. 

I strongly concur with the proposal made in the document to rely on a vocabulary for time_origin. In this case, we can solve the previous issue by simply naming the observatory by its name. 
It is then a client's job (or user's job) to rebuild an actual location from the named time_orgin and the actual time value, for instance using the SPICE kernel library for NASA or ESA operated planetary missions. It may not be straightforward, but at least all the pieces of information are present to do so.

The work done by Semantics and SSIG on the Observation Facility nomenclature would clearly help in this respect. 

Baptiste

> Le 31 oct. 2018 à 13:55, Tom McGlynn <Tom.McGlynn at nasa.gov> a écrit :
> 
> 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/
>> 
>> 
>> Thanks for taking the time to read this document,
>> 
>> Happy reading!
>> 
>> See you in College Park,
>> Ada Nebot
>> TDIG Chair
>> 
>