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[aprssig] ISS Tracking & Pass Information

Lynn W. Deffenbaugh (Mr) ldeffenb at homeside.to
Fri Oct 14 10:14:49 UTC 2011

Pardon the tone of the following response.  I haven't had my Mt. Dew yet...

I'll read through and consider your suggestions, but you obviously 
haven't even TRIED the service before commenting on the formatting.  
Give a deveoper a break and comment on what you SEE and not what you 
THINK you read!

The "z" is NOT for zulu, but was an unfortunate placholder choice.  Note 
that it said xx:yyz, not hh:mmz?  The delta time calculation may be 
things like:

1:25h - Means 1 hour 25 minutes (hourly presentation)
45:24m - Means 45 minutes 24 seconds (minutes presentation)
30s - Means 30 seconds (obvious)

This is used both for both AOS/LOS as well as for pass durations on the 
AOS.  And in my watching, durations are NOT always in minutes, but can 
be less than one minute for horizon skimming passes.  It's just that 
satellite operators "know" to ignore those that never get above 1 degree 
MaxEL, but it's still a pass hence the provision for the seconds 
transmission.   Not to mention the fact that LOS may be in 10 seconds 
when you query.

As for these messages needing to include the satellite name because 
they'll be "sitting in the inbox", c'mon.  By that argument I should 
include year month and day which totally eliminates your suggestion of 
shorter packets by removing colons from timestamps.  If someone queries 
a satellite for a pass, they're expecting and will receive the answer in 
short order. It won't just sit around.  And if it arrives too much 
later, it will probably be particularly useless and they'll just query 
again for the current situation.  So, unless there's an overwhelming 
outcry, I think I'll stick with delta times (with no confusing "z").

I'll try considering the various small screens, but the human brain is 
quite adept at putting together multi-line text.  And there's no 
guarantee that the spaces added to fit the current crop of APRS radios 
isn't going to completely hose the next cheap APRS radio that comes out 
with a 9 character wide screen, or the HamHUD user, or the Nuvi350.  
There's a lot more ways to do messaging than a Kenwood D7* or a Yeasu 
radio.  Besides, again, eliminating a colon from a timestamp and then 
throwing in multiple spaces to pad a display are conflicting goals.

I'm not trying to support the serious satellite users.  They've already 
got their own schedules and pass prediction software running.  I'm 
trying to get a simple, quick, easy-to-use PORTABLE way of getting basic 
pass information.

I went with a pass duration rather than max elevation so novices can 
better plan their time investment.  They both basically communicate pass 
"quality" and "ease of working", but everyone understands time, while 
the experts have a handle on elevation, but again, they have their own 
tools.  Besides +duration is a lot shorter than "MaxEL nn deg".  I've 
definitely experienced the fact that shorter messages deliver over RF 
more reliably.

I will look at not requiring the dash in the satellite name.  That was 
in my plans, but I haven't gotten it implemented yet.

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

On 10/14/2011 12:05 AM, Bob Bruninga wrote:
> Great project!
> But the format for zulu time is HHMMz.  there is no colon.  And it saves bandwidth too.
>> send an APRS message to ISS... The response will be:
>> Az: aaa El: lll LOS:xx:yyz - If you are in a pass
>> AOS: xx:yyz+aa:bbc - If you are not in a pass
>> AOS: NONE - If... no passes... in... two days.
> I wonder if we could tweak the format to not be so choppy or to better match some radios small 12x12x12x10 display windows... (D7).   I'd suggest:
> AZ/EL aaa/LL LOS: X min
> AOS ISS in HH:MM MaxEL yy deg
> Duration is always going to be in minutes and I'd rather see a relative time, rather than try to think in zulu and not be sure.  This tells you how long till the next pass and what its max elevation will be.  Anyone who operates the satellites can infer how long it will last from the maximum elevation angle and whethter it is a pass worth listening to or not...
>> You can send an APRS message to "AO-51"
>> to find out when that satellite will pass within
>> range.
> You might consider dropping the requirment for the HYPHEN.  In all my earlier APRS/space applications I truncated the names to 4 bytes and eliminated hyphens... mostly because they are wasted characters and take a lot of button pushing to get the "-" character...
>> Give the service a try...
> It is a great concept!!!
> One disadvantage of the time-to-go approach is that the message sits in your message buffer and for use later,  you haev to mremmebr when it came in.  Maybe it is better your way.  In that case, I'd suggest:
> AOS ISS_ at HHMMz MaxEL yy deg
> Notice that you need the satellite name (typically truncated to 4 bytes) so that these messages make sense later.
> Great work!
> Bob, WB4APR
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