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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