On Jul 17, 9:08*pm, Hellman wrote:
On Jul 16, 7:48*am, Steve Koerner wrote:

I did a serious investigation on the problem involving some
experiments and analysis and I made a presentation to my local club.
My presentation is available for download from my Wing Rigger website:www.wingrigger.com. *(click Extra Soaring Content in lower right
corner).

Steve,

Thanks for that detailed analysis of SPOT behavior. While it helps in
understanding SPOT generally, my question -- and big concern -- is why
that flight was different from all other flights. I don't believe I've
never had more than a 30 minute gap (2 missed transmissions) before,
yet this time the gap was 90 minutes (8 missed transmissions). I was
asking if anyone else had a track from that specific day and time (JUL
15, 1900-2020 Z) and general location (roughly from Oakland, CA to
Lake Tahoe). If so, I wanted to know if they had coverage or also had
around a 90 minute hole in their data.

Martin

Martin

You want to end the guessing game and tell us where your SPOT
messenger is mounted? On your harness? On your shoulder? Obstructed
by your head? What is the effective field of view of the antenna?

You were tracking roughly the same heading for all that time. And
that heading (very) roughly lines up with one of the inclined planes
of the GlobalStar constellation.

The GlobalStar satelites orbit in a interweaved pattern with two
inclined planes at +/- 80 degrees or so (you can see a simulation here
http://www.youtube.com/watch?v=G8VPEueequM or you can actually play
with the SaVi software shown in the video, see http://savi.sourceforge.net)..
It is quite possible that things happen like the satelites flying from
the south west to north east are obscured over your left shoudler if
say your SPOT messenger was to the right side of your head and all
those passes could be obscured and maye the next parallel path to the
east is too far away. That leaves the satellites tracking north-west
to south-east and just maybe again if your head partially obscured
those then the satellite does not see the spot until it is further
overhead and out of the optimal bent-pipe geometry to reach the
Alberta, Canada ground station. So maybe in the whole time you just
get maybe one shot when the SPOT fires off its track message where it
manages to see a satellite to get it a bent path to the Texas ground
station. Maybe you just managed to get things timed so bad that you
never happened to have a satellite with bent-pipe view to any ground
station when your SPOT happened to fire the TRACK message.

This is all very uninteresting if the SPOT messenger is mounted say on
your parachute harness and inclined or significantly obscured. Tell me
it is out flat in the open and I'll actually care.

Darryl