[amsat-bb] Gold Standard for Keplerian Data

Steve May steve.w5iem at gmail.com
Mon Nov 24 04:21:49 UTC 2014

I appreciate the suggestions. After a long day at work I have sat down this
evening to look at the system, but I am still stumped.

I am using a Windows 8.1 system, and the clock appears to be synchronized
correctly. I am letting Windows set it automatically, and when I look at my
cell phone the two display the same time and the minutes change

The Keps seem to be updated correctly, and it shows that they are looking
at the file that was updated earlier today. I looked in the directory and
the updated nasa.all file is there.

The time seems to be incorrect for all of the satellites I am trying to
predict. Since I am only concerned with AO-7, FO-29, AO-73, and SO-50 they
are the only ones I a running a prediction for, and since I am pretty new a
this I am trying to use a 15-degree minimum elevation.

I am generating a WinAos list, and it seems to be pretty much across the
board hat the predictions in the WinAos software are about 5-6 minutes
later than the predictions from the AMSAT website. Some of the predictions
show a 1-degree difference in max elevation as well, although it isn't on
every pass. These inconsistencies are probably based on rounding.

It is showing this difference in time on every satellite in the predictions
as well.

I have checked and double-checked the Observer location on both predictions
and I am using the correct location, EM78re. I have tried it on both
predictions to enter the 6-digit grid square location as well as putting in
the GPS coordinates manually and it doesn't seem to change anything.

I am stumped by this. I assume it has to be something in my SatPC32 setup,
and I will try it at work tomorrow on a different machine to see if the
errors are the same.

Any other suggestions?

Steve, W5IEM

On Sun Nov 23 2014 at 12:45:34 PM Erich Eichmann <erich.eichmann at t-online.de>

> Steve,
> I compared the results of the pass prediction from the AMSAT website for
> the next 10 passes of FO-29 with the results of WinListen (that comes
> with SatPC32) for my location (8.9 degrees east, 51.94 north). The
> results are exactly the same (WinListen rounds the AOS/LOS times to the
> closest full minute, however). It requires to enter and save your QTH
> locator or longitude/latitude.   I used the latest file nasa.all as Keps
> file.
> in most cases of different results between the AMSAT pass precition and
> SatPC32  wrong longitude/latitude values in menu "Setup", "Observer" or
> "Setup" of WinListen or  different  Keplerian data were the reason.
> What is your 6-digit QTH locator (or longitude west and latitude
> north)?  What is the entry in SatPC32, menu "Observer" and in WinListen,
> menu "Setup"?
>   What Keps file do you use?  Download  the Keps file you use from
> SatPC32 menu "Satellites", "Update Keps". When the download is
> successful click "Quit" and then "OK". The path to the Keps files folder
> can be seen in the foot line of menu "Satellites", the file date in the
> bottom line of the SatPC32 main window and in the left list of the menu
> you can choose the file. WinListen will use the same same path (foot
> line in menu "Listen").
> 73, Erich, DK1TB
> Am 23.11.2014 17:04, schrieb Steve May:
> > I have noticed that when I update the Keplerian Data for my location on
> > SatPC32 and generate a list of passes they all seem to be about 5 minutes
> > different than the predictions from the AMSAT website. This is for the
> > earliest pass, and I am using the exact GPS coordinates for my location.
> >
> > So which do I rely on? Which predictions should I consider the "gold
> > standard" for passes?
> >
> > Steve, W5IEM
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