A modest proposal for VOEvent

[Arnold Rots]

Still reinventing the wheel, uh?

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Rob Seaman wrote:
> Hi Bob,
> 
> I'm all for promoting adoption of prevetted standards.  MPC 1-line  
> format represents a C-like struct datatype.  Maybe this is something  
> to support, or maybe the XML-ness of breaking it out into explicit  
> variables should win out.  Arguments from both sides?
> 
> Rob
> ----
> 
> On Feb 22, 2009, at 5:42 PM, Bob Denny wrote:
> 
> > Rick Hessman:
> >> I believe the thing to avoid is
> >>
> >> 	<orbitalElements q="1.2345" P="9.54321" Punits="days" ...   />
> >>
> >> as too compact and illegible...
> >
> > and the values cannot be validated by a schema-driven parser. I  
> > agree that this
> > is the wrong way to go!
> >
> >> ... and
> >> 	<orbitalElements>
> >> 		<q>
> >> 			<units>none</units>
> >> 			<value>1.2345</value>
> >> 			...
> >> 		</q>
> >> 		...
> >> 	</orbitalElements>
> >>
> >> as too verbose and cumbersome to parse.
> >
> > Also agreed. It's the opposite end of the spectrum and just as bad.
> >
> >> The only reasonable system
> >> is to use attributes for secondary information, e.g.
> >>
> >> 	<orbitalElements>
> >> 		<q units="none">1.2345</q>
> >> 		<P units="days">9.54321</P>
> >> 	</orbitalElements>
> >>
> >> but then, everyone has their own tastes (and those tastes even  
> >> change).
> >
> > I'm a KISS Principle guy. The MPC has standard formats for numbered  
> > asteroid and
> > cometary elements already, the so-called "1-line" format(s).  
> > Everyone knows what
> > these are, how they are formatted, and what units they are in.  
> > They've been
> > around for many years. MP versus cometary can be determined by  
> > inspection. So
> > something as simple as
> >
> >   <orbitalElements>K01FI5V  7.7   0.15 K014L   0.10308 ...</ 
> > orbitalElements>
> >   <orbitalElements>    PJ97T030  1998 03  9.3751  ...</ 
> > orbitalElements>
> >
> > would carry everything there is to know about the elements. If only  
> > the number
> > or designator is given, that could automatically reference the MPC's  
> > orbital
> > elements database. That would provide the "latest" elements if that  
> > were
> > preferable (maybe you want to specify the elements that WERE used  
> > and not the
> > elements TO use). So
> >
> >   <orbitalElements>K01FI5V</orbitalElements>
> >   <orbitalElements>0029P</orbitalElements>
> >
> > Now what about NEOs which have only a rough short-arc orbit, and for  
> > which there
> > are no elements available? I've successfully used the MPC's "NEOCP  
> > Ephemeris"
> > format. Needless to say, the position of an NEO is not well known  
> > very far
> > ahead, so this would apply only to timely observations in response  
> > to a VOEvent.
> > In that case, some ephemeris lines covering the expected validity  
> > period of the
> > event, spaced an hour or two apart, should be "good enough". One can  
> > do
> > something like a Lagrange interpolation over that data and get a  
> > pretty good
> > position. So something like
> >
> >   <ephemeris name="A123456789">
> >      <pos>2004 10 27 02    01.6915    -40.095</pos>
> >      <pos>2004 10 27 03    01.6834    -40.167</pos>
> >      ...
> >   <ephemeris>
> >
> >  -- Bob
> >
> 
--------------------------------------------------------------------------
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 head.cfa.harvard.edu
USA                                     http://hea-www.harvard.edu/~arots/
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