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[aprssig] Satellite positions: FREQUENCY

Lynn W. Deffenbaugh (Mr) ldeffenb at homeside.to
Wed Oct 19 17:10:15 UTC 2011


On 10/19/2011 12:15 PM, Bill Vodall wrote:
>
> I'm trying to offer a globally-accessible satellite information service.
> It will be good and I'd be taking advantage of it today if it were
> running.   There are a couple tweaks to the system I will be
> suggesting...

It IS running.  Just send an APRS message to ISS or any other satellite 
designator and, provided you've recently (within 2 hours) beaconed a 
position for the requesting station, you'll receive information on the 
next pass of the queried satellite.

> This is very good but please keep in mind what happens at the local RF
> level and build your system to complement that...

Precisely why the centralized system is designed to be a message 
query/response only.  No pseudo-stations involved at this time.

> This is a real weak point in our APRS system.   That's another discussion.

I'm working to provide information based on the current APRS network 
capabilities.

> Also the Igates can selectively do the 'igating...'   The Poll model
> useful at some times but for an ongoing use I hope the objects will be
> available continuously without polling..

Personally, I'd disagree with that one, but that's not part of my 
current query/response design anyway.  I'm a firm believer in 
"information on demand" and not "flood the airways with information that 
one or two people might want to know in the hopes that they happen to 
receive it".  Subscription vs broadcast model.

> Suggestions:
>
> I would suggest that you set up a dedicated server alias to generate
> the objects.   It could respond to the simple name queries like "iss"
> but it could also respond to its own name.

I generate no objects, just response messages.  And I'm considering an 
advanced-query-capable "server" (SATS was suggested, which I might use, 
but I was also considering SATSRV).  But in any case, I'll probably be 
keeping the simple "send any APRS message to the Satellite" for simple 
next pass information.

> Use a uniquely coded name for the objects generated.  'ISS' will be
> used by the local servers so you could key all your objects with
> something like 'is*'  - thus you would generate 'isISS'.  This would
> also allow folks to gate the objects to RF based either on the name of
> 'is*' or on the alias of the server generating them.

I researched the occurrences (or lack thereof) of the satellite names as 
objects before launching (no pun intended) the current service.  All 
local objects seem to be suffixing the object names with the AOS time 
which keeps us all unique.

> What happens if the server goes down?   Will there be a hot spare at
> some other location watching and ready to take up the load?

Depends on the popularity.  Is there a hot backup for CQSRVR?  Or 
EMAIL-2?  Or WHO-IS?  Yes, I know there are redundant services by 
different names, but AFAIK no immediate backups for the main names.  Is 
there a backup for your local IGate?

> What happens it you get tired of this silly game and decide to go work
> CW?   Will we lose the resource as has happened before?

I sure hope not, but the same question can be asked of local digis, 
IGates, and nearly everything else within APRS, right?  I do plan to put 
in a migration plan to cover my inevitable demise (which not not involve 
destruction of ANYTHING) or waning interest in APRS, but that's not 
anytime in the foreseeable future.

> Thanks again for all your energy and efforts here..   You've brought a
> spark of new life to the system.

You're welcome.  It's all about having ideas and implementing them and 
sharing the results.

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




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