Hi Loren and all,
The times that are being posted are being given by
ARISS to the schools. The schools are to confirm the times
themselves using the very latest Kep data that they have
acquired on the day of their contact. The schools have to
realize that things can change a few minutes plus/minus from
what they may have planned for the event.
My latest prediction that I get using the very latest
files from Celestrak are showing:
AOS 18:45:31 UTC LOS 18:56:12 UTC Max elevation 32
degrees. I am using the exact coordinates that the school
gave us for where the event is being held. The software I
am using for this prediction is Nova. So it looks like your
predictions are very close.
Like I have said in earlier emails, the times that
show up on the AMSAT-BB are really to be thought of as more
of a planning/placeholder time. If there is a major change
in the contact time, then the bulletins get updated to
reflect that change. I have lost count how many times I
have done that. Again, I always say to either run your own
Keps or to plan on starting to listen about 10 minutes ahead
of what gets posted. I don't try to keep the times updated
every day; I am simply too busy with all of the ARISS work
to do that. If there is something major, then I posted
something.
Please also note that depending on the local school
location versus terrain, the ISS antenna versus the ISS
superstructure itself maybe blocking the signal, and a
zillion other reasons; the actual conversation might start
30 to 60 seconds beyond predicted AOS. And the contact
might end sooner than expected. We have had a few times
where the contact actually got started before predicted
AOS. So I always recommend to my schools to start calling
the ISS 30 to 60 seconds ahead of predicted AOS and to have
the squelch fully off so that they can hear the faintest of
signals. Believe it or not, you should hear a slight
decrease in the background noise as the signal is working
towards full quieting but hear no audio just yet. That's
when I know we probably got them, they are calling us, but
we just don't hear the audio yet. Wait a few more seconds
and then there they are. Once a school hears some actual
audio, then you can usually sense a big sigh of relief from
the audience.
Also in my earlier email, I mention that our lead
orbital guy is using Kep data that is not in the public
domain. So yes, he is getting data from NASA on what is
happening and what is planned to happen. As the contact
date and time approaches real time, the latest public domain
Kep set is what is in command of the actual prediction. And
of course, the ISS is the one really in command as to where
it is traveling.
Hope this helps.
73,
Charlie Sufana AJ9N
One of the ARISS mentors
In a message dated 2023-02-06 12:06:27 Eastern Standard Time,
amsat-bb@amsat.org writes:
I actually took the time to set the home location
to the GPS coordinates of K7IVM as the home location
and I took a screen shot from the website when I was
preparing last Tuesday. It clearly shows the home
location somewhere near Millville, UT and the AOS
being 20-30 seconds before 18:42. Pulling up that same
pass today, I see the AOS is 18:45:40 and it still
shows the house on K7IVM's location near Millville.
I'm pretty certain they've updated their prediction,
but I'm just not sure if their earlier prediction was
based on a less reliable or older source than the
original ARISS announcement, or if the ARISS
announcement, when it was first written up (since I've
never seen the time waiver) was just lucky to be
closer to these more recent predictions from N2YO. I'm
not sure where they get their information from, but I
just found it a curiosity as I can imagine ARISS
having access to more insider info like future burns
than would be in public TLEs.
-Loren
K7IW
N2YO is
giving you the AOS time for. your location --
assuming you have it set up properly. ARISS is
giving the time for the contacting ground station.
I'm not sure how much time ARISS schedules after
AOS to begin the contact.
--
Mark D. Johns, KØJM
AMSAT Ambassador & News Service Editor
Brooklyn Park, MN USA EN35hd
-----------------------------------------------
"Heaven goes by favor; if it went by
merit,
you would stay out and your dog
would go in."
---Mark Twain
Are the questions for Tuesday's ISS School
contact posted somewhere or possibly a live
feed?
Also, I had noticed last week that the
beginning of contact time as predicted on
N2YO.com was
about 4 minutes earlier than the ARISS
bulletin had it. Now that it's a few days
later, N2YO has an updated AOS time that is
much closer to the time on ARISS which hasn't
changed. I originally assumed that N2YO would
be more accurate than the time posted on a
static timeline, but now I'm wondering if
ARISS has more insider details than are
available from the public TLEs or if N2YO was
just using an older data source.
-Loren
K7IW
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