Re: Re: Tracking program.

Bruno Tilgner (
Wed, 17 Jun 1998 15:22:30 EDT

In a message dated 6/17/98 9:43:03 AM, you wrote:

<<>I have been looking for a sat tracking program that will show a real time
>sky-trace of one or a list of satellites. I am trying out SatSpy 2.5,
>which has a multiple sky trace feature, but it is for a pre-determined
>time span and not real-time tracking.
>I would appreciate any suggestions.>>

I'd agree with the advice re SkyChart 2000 v 2.7, and Starry Night.  I think
the freeware planetarium software Home Planet can also approximate a real time
display, but just 1 sat at a time.

SkyChart 2000 readily imports large N2L files, so viewing a constellation such
as GPS, Iridium, NOAA, etc is easy.  It gives decent magnitude estimates,
excluding glint/flare phenomena.   But there is no way to delete them once
saved to the database, so think twice before saving your database with
thousands of elsets when you quit the program.  It is not difficult to import
them for each run.  For speed, it uses an SGP model, which is a bit less
accurate than SGP4 used in most sat tracking software.  The Earth's disk is
drawn over satellite trails, so viewing the Mir orbit from above won't work
well.  Animation controls are very flexible.  Trails do not indicate shadow
passage like in SatSpy, you have to watch the magnitude in an info window.

Starry Night requires you to paste elements one line at a time, so isn't
practical for large numbers of satellites.  Magnitudes need fiddling to get
them faint enough.   Leigh Palmer, didn't you  mention difficulty getting sats
in shadow to indicate properly?  Animation works well, put in 0.0 for the step
time to get it to run as fast as possible on your machine.  You can save a
Quicktime movie, which is nice for orbit demonstrations.  Jim Cook identified
a problem with the occasional elsets containing a negative drag term; fresh
elements work well if you delete the minus sign.

Starry Night is prettier, works fine if you have a few sats to watch.  If you
want to animate dozens of sats, I'd go with SkyChart 2000.