<html><head><meta http-equiv="Content-Type" content="text/html; charset=utf-8"></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; line-break: after-white-space;" class="">Hi, Tom, Arnold, <div class=""><br class=""></div><div class="">I agree that saying UNKOWN seems to be unfair. The term TOPOCENTER can be referred to the location of the instrument as Arnold mentions. </div><div class="">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. </div><div class="">Including ephemerides on the other hand, and in my opinion, would be complicating things for this simple annotation. </div><div class=""><br class=""></div><div class="">We are taking into account the comments we are receiving and I propose to move the discussion to Apps for the more technical details. </div><div class=""><br class=""></div><div class="">Cheers,</div><div class="">Ada</div><div><br class=""><blockquote type="cite" class=""><div class="">On 1 Nov 2018, at 20:20, Arnold Rots <<a href="mailto:arots@cfa.harvard.edu" class="">arots@cfa.harvard.edu</a>> wrote:</div><br class="Apple-interchange-newline"><div class=""><div dir="ltr" class=""><div class="">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).</div><div class="">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.</div><div class=""><br class=""></div><div class="">Cheers,</div><div class=""><br class=""></div><div class=""> - Arnold</div><div class=""><br class=""></div><div class=""><div class=""><div dir="ltr" class="gmail_signature" data-smartmail="gmail_signature"><div dir="ltr" class="">-------------------------------------------------------------------------------------------------------------<br class="">Arnold H. Rots Chandra X-ray Science Center<br class="">Smithsonian Astrophysical Observatory tel: +1 617 496 7701<br class="">60 Garden Street, MS 67 fax: +1 617 495 7356<br class="">Cambridge, MA 02138 <a href="mailto:arots@cfa.harvard.edu" target="_blank" class="">arots@cfa.harvard.edu</a><br class="">USA <a href="http://hea-www.harvard.edu/~arots/" target="_blank" class="">http://hea-www.harvard.edu/~arots/</a><br class="">--------------------------------------------------------------------------------------------------------------<br class=""><br class=""></div></div></div><br class=""></div></div><br class=""><div class="gmail_quote"><div dir="ltr" class="">On Wed, Oct 31, 2018 at 3:55 PM Tom McGlynn <<a href="mailto:tom.mcglynn@nasa.gov" class="">tom.mcglynn@nasa.gov</a>> wrote:<br class=""></div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">It seems to me that this makes no accommodation for satellites where the <br class="">
reference position is variable but not<br class="">
unknown. The definition of topocentric is according to my dictionary: <br class="">
"**relating to, measured from, or as if observed from a particular point <br class="">
on the earth's surface *: *having or relating to such a point as origin" <br class="">
so TOPOCENTER is fine for earth based observations (though there are <br class="">
balloons that move quite a bit during an observation campaign) but it <br class="">
would be a stretch to use it for satellites. I wouldn't want to say <br class="">
UNKNOWN though. Maybe SATELLITE or VARIABLE? Lots of HEASARC data <br class="">
have times that are measured at the satellite -- and that includes lots <br class="">
of the GRB detecting satellites for which this kind of feature would be <br class="">
very nice.<br class="">
<br class="">
Tom McG.<br class="">
<br class="">
AdaNebot wrote:<br class="">
> Dear All,<br class="">
><br class="">
> A Note entitled “*A Proposal for a TIMESYS Element in VOTable*” can be <br class="">
> found under:<br class="">
><br class="">
> <a href="http://ivoa.net/documents/Notes/TimeSys/" rel="noreferrer" target="_blank" class="">http://ivoa.net/documents/Notes/TimeSys/</a><br class="">
><br class="">
><br class="">
> Thanks for taking the time to read this document,<br class="">
><br class="">
> Happy reading!<br class="">
><br class="">
> See you in College Park,<br class="">
> Ada Nebot<br class="">
> TDIG Chair<br class="">
><br class="">
<br class="">
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