Re: ISS satellite tracking help please?


Greg D
 

ISS pass was perfectly (within a second) aligned between APRSIS32 and Gpredict.  They appear to agree on the next pass (ok, 4 seconds earlier for APRSIS32)... 

How long did it take for the ISS predictions to drift significantly?

Greg  KO6TH


Greg D wrote:

I've had pretty good luck with Celestrak's Keps, but yes, if they're off it will propagate.  They're kind of the headwaters for satellite data.

The only other thing to consider is that for very low passes, one prediction program might see a pass, where another might not.  This is both from differences in the prediction algorithm and age of the Keps, as well as a bit of configuration where some programs intentionally ignore passes below some configured elevation.  The next pass of the ISS, for example, didn't show up on my usual tracking software's "next pass" view, since it's only 3 degrees, so I was initially thinking there was a problem.  Viewing all upcoming passes brought it up, and confirmed agreement with APRSIS32.

An hour in, and we're still looking good...  The ISS pass is at about 4:27pm local; let's see what happens then.

Greg  KO6TH


'Fred Hillhouse' fmhillhouse@... [aprsisce] wrote:
 

I looked at the ISS this morning and compared it against Heavens-above and Orbitron. It all looked good. But then just about all my satellite tracking software (Orbitron, PocketSat) uses the TLEs from Celestrak. So if the TLEs are wrong, then everything would be as well.

 

There is often “time” confusion that comes up and it is usually the difference in acquisition time. It usually differs because of the angle in which it is determined. The timing is not that significant when comparing 0deg elevation or 15deg elevation. The 12 or so that the original poster mentions is something different.

 

In general, an update to TLEs don’t need to be updated more than once a week or so. Most antennas have a fairly wide capture angle so a few degrees of difference is not significant.

 

I don’t recall if APRSIS32 reloads the TLE automatically. That would be a handy feature if it doesn’t.

 

Best regards,

Fred N7FMH

 

 

 

From: aprsisce@... [mailto:aprsisce@...]
Sent: Monday, October 03, 2016 1:27 PM
To: aprsisce@...
Subject: Re: [aprsisce] ISS satellite tracking help please?

 

 

Thar it be!

Ok.  Prediction for FO-29 is pretty much spot on (comparing with Gpredict).  ISS looks pretty close too.  I'll let it run for a bit, and see what happens.

Greg  KO6TH

'Fred Hillhouse' fmhillhouse@... [aprsisce] wrote:

 

This might be it:

http://aprsisce.wikidot.com/doc:satellite-tracking

 

Best regards,

Fred N7FMH

 

From: aprsisce@... [mailto:aprsisce@...]
Sent: Monday, October 03, 2016 12:55 PM
To: aprsisce@...
Subject: Re: [aprsisce] ISS satellite tracking help please?

 

 

Hi Michael,

The clock thing wasn't so much asking if it's super accurate, rather, has it gotten stuck?  Years ago (and a few generations back on Windows software) I had some program that would get knotted up on occasion, and would cause the clock to stop updating like it should.  I think it was spinning on some I/O port.  Caused multiple minutes of delay, sometimes an hour or so.  VERY obvious, just looking at the clock icon on the task bar.  That kind of clock problem...  I have no idea if Win-10 could even have that possibility, as the I/O model is totally different now.

So, let me try it here...  Where exactly is the ISS tracking config?  Again, I remember trying it years ago, but have lost the recipe on how to do it.

Greg  KO6TH


mkellync@... [aprsisce] wrote:

 

Great question about the clock, but I run a standalone atomic clock on the bench next to my computer and that is not the issue .... although I had not even thought about that and was encouraged when you gave me the idea, so just to make sure I setup a program to automatically sync my windows 10 using this: http://www.worldtimeserver.com/atomic-clock/ 

 

I will check it again later, as I set this up to sync every 4 hours and see if the tracking is better ... but yes, I am using APRSIS32 as my tracking software, but I also have SatPC32 v. 12.8c that I use to check against the APRSIS32 location.  I am used to having to update Keps every few days ... but not every few hours.

 

Something is amiss Watson!  Any suggestions are welcome.

 

73, Michael nz4d

 

 


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