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RE: Did they ever fix the orbit number?



Bob and Maggie had this dialogue:

> On Sat, 15 Sep 2001, Margaret Leber wrote:
>
> > On Saturday 15 September 2001 18:59, Bob Bruninga wrote:
> >
> > > What software requires ORBIT Number to work right?
> >
> > Well, even though it's not an absolute requirement, it would be nice if
> > the tracking and the telemetry were in sync...that way we'd all know
> > which orbit was being talked about.
>
> Thanks.  Someone had told me that their program would not give a good
> track on PCsat using the  pre-launch keps because they did not have an
> orbit number.  I was reacting to that, when I saw the question about orbit
> numbers.

This problem has been around for many, many, many years; I'll repeat the
essence of my answer to those who raised the issue back in the bygone days
of yore when the issue came up concerning my original ORBIT program. Most of
the concern back then was to answer the question "What orbit ## do  I put on
my QSL cards?".

The first discrepancy, amounting to one or two orbits, begins on launch
date:
 (a)Is the first birthing orbit number zero or number one?

       The consensus answer and convention followed in all software I know
       about is ZERO

 (b)How do you count orbits while the satellite is still attached to the
    launch vehicle?

       The consensus answer was that orbits while attached to the launch
       vehicle count. At separation, the satellite and launcher have
identical
       parameters.

 (c)Where in the orbit do you increment the number? At Perigee (i.e. MA=0)?

       The answer is NO, it is not at MA=0 -- Conventions dictate that the
       number be bumped at the instant when the satellite crosses the
equator
       northbound. AMSAT's use of this definition goes all the way back into
       the 70's when Skip Reymann (W6PAJ), Dave Mills (W3HCF) and I put
       together the old AO6/7 annual "Orbit Book" to use with K2ZRO's
plotter
       and desk calculators for simple circular orbits. The book had Orbit
Rev
       number plus the date/time and longitude for each equator crossing.


NORAD/NASA place zero priority on the orbit rev number in their two-line
elements (TLE). IMHO, nobody but amateurs RGAS (Really Give A S**T). I doubt
that an appeal to NORAD/NASA will do any good. And if, by chance, you do get
it fixed, I can guarantee that the problem will recur in a few
days/weeks/months/years.

My recommendation is, and always has been, that folks who care about such an
issue should use the truly invariant parameter, date/time for purposes like
QSL cards, TLM logging etc.

73 de Tom, W3IWI

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