[aprssig] Satellite Predictions requires a) Beacon and b) Messaging IGate

Bob Bruninga bruninga at usna.edu
Tue Oct 18 11:11:42 CDT 2011

I'm still a little uncomfortable with the time formats:

AOS in 6:45h for 9:50m MaxEL 27

1)  Because I have not normally seen 6:45h refer to 6 hours and 45 minutes
nor have I see 9:50m refer generally to 9 minutes and 50 seconds.  So that
is kinda unusual to see...

2) No mobile is ever going to see a 9:50 minute pass.  Mobies cannot work
down to the horizon even if they are sitting on a mountain, because the
satellite is 10dB farther away at that point, and impossible to work with an
OMNI mobile antenna.  (the intended audience for this info).

If the pass  is 9m 50s, then the typical useable portion of the pass (where
it is at least 6 dB closer) is going to be maybe 3 to 5 minutes.  It does
not make a lot of sense to provide seconds of precision to such a very
imprecise effect.  I'd really like to see that rounded to "9m"

Although I do not feel comfortable with 6:45h I am less comfortable with
"6.75h" but is more consistent.  If you want to mix minutes and seconds you
could use 6h 45m.  Though I don't like that either.  As you know, I like
indicating it as a specific TIME if it is more than an hour away or in delta
minutes of it is less than an hour.

> AOS in 37m for 9m MaxEL 27 (or)
> AOS at 1425z for 9m MaxEL 27 (or)

Actually, I would make the separation be at 99 minutes.   This is because
all LEO satellites have periods on the order of 90 to 100 minutes, so if it
is less than 100 minutes away, then it is the next pass.  If it is more than
99 m inutes away, then it is quite a while.

Though if you do not like making the distinction between "AOS in..." and
"AOS at..." I suppose you could compromise with both:

AOS in 405m at 1425z for 9m MaxEL 27

Bob, Wb4APR

-----Original Message-----
From: aprssig-bounces at tapr.org [mailto:aprssig-bounces at tapr.org] On Behalf
Of Lynn W. Deffenbaugh (Mr)
Sent: Monday, October 17, 2011 2:02 PM
To: TAPR APRS Mailing List
Subject: [aprssig] Satellite Predictions requires a) Beacon and b) Messaging

A reminder: For the satellite pass query to work from RF, you MUST have
beaconed a position AND be within range of a bi-directional,
message-passing IGate.

I tried to track down a direct contact for LA9IRA who has been trying
and trying (from LA9IRA-9) to get a pass prediction for the ISS.
However, it appears that LA9IRA-9:

a) has not beaconed a position since 2011-06-03 13:36:22 UTC (136 days
ago) (http://aprs.fi/info/LA9IRA-9)

b) is not in range of a message-gating IGate (based on retries

Here's the message trace from the SATSRV server for the most recent attempt:

2011-10-17T17:38:18.427 LA9IRA-9>ISS a{0
2011-10-17T17:38:18.428 ISS>LA9IRA-9 Please Beacon Position
2011-10-17T17:41:18.057 LA9IRA-9>ISS a{0
2011-10-17T17:41:18.057 ISS>LA9IRA-9 Please Beacon Position
2011-10-17T17:43:26.312 LA9IRA-9>ISS a{0
2011-10-17T17:43:26.312 ISS>LA9IRA-9 Please Beacon Position
2011-10-17T17:44:25.659 LA9IRA-9>ISS a{0
2011-10-17T17:44:25.659 ISS>LA9IRA-9 Please Beacon Position

If anyone knows of a way to contact Christian Langgard (from qrz.com,
but no e-mail there), please forward this message on to him/her so as to
not end up with a disgruntled user that believes the ISS query server
just plain doesn't work.  It does, IF you tell it where you are and can
hear it's responses.

Lynn (D) - KJ4ERJ - Author of APRSISCE for Windows Mobile and Win32

PS.  If you're trying to use the ISS pass predictor and aren't getting
an answer, you can always check the raw packets at
http://aprs.fi/?c=raw&call=ISS&limit=25&view=normal to see the server
side of what's happening.   Substitute whatever satellite you are
addressing for "ISS" in that URL.

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