[amsat-bb] SimpleSat - a slight variation on the SatPC32 Observer2 module

Thomas Doyle tomdoyle1948 at gmail.com
Fri Oct 7 16:03:19 PDT 2011

I am looking for someone who will read a small amount documentation and has
lots of experience and a little time to check out a program I have written.
It seems to work but I have a question about it. It looks for possible
satellite passes where communications between two different grid locations
is possible. Back in the day it was a real challenge to work Hawaii - I
remember pouring over mounds of paper trying to find a pass that would work.
It was a real thrill when it actually worked. I thought it would be
interesting to write a little program to automate the process. You are
probably thinking - I have a great csh script that was written by Harold
that would do it. I am not looking for another program I am just trying to
determine if mine is working correctly. The Observer 2 module in SatPC32
served as a starting point.

After I wrote it and was testing it I found that it took a while to find a
pass when you are operating on the limit of coverage or if there are no
valid passes. It is the age old question - when looking for something how do
you know if it does not exist or if you have just not looked long enough. I
decided to try and eliminate the satellites that simply would not work based
on the distance between the two locations. It was fairly straightforward to
use the TLE data to calculate the altitude and from that the central angle
and from that the "width of swath". I found the "width of swath" term in a
reference and think it is the only really cool term in orbit mechanics. I am
not sure my "width of swath" value is correct. I first tried checking it by
looking at the SatPC32 3D display and visually comparing the width of the
range circle to the width of South America - this seemed fairly close. After
the program was working I found that when the distance between the two
locations was less than the "width of swath" a valid pass was found and when
it the distance was greater there were no valid passes so I am fairly sure
it is at least close. The program displays TLE generated altitude, central
angle and "width of swath" for each of the satellites it is using in the
search. If someone could take a peek at these values and let me know if they
think they are correct I would appreciate it. The program does not use these
values it just displays them. At present the program searches every quarter
second over a 1 week time period to find a pass. If I am sure the "width of
swath" value is correct I will eliminate the passes that have no chance and
extend the search time.

The program uses .NET and is very easy to use. Ease of use has always been
an interest of mine so this is about as easy as it gets. There is a help
file accessible from the help menu. Reading it before you try it out would
be a good idea.

You can download the program from here. It is a zip file. Un-Zip the files
it into a folder and run the SimpleSat.exe file. No install is required and
the three files it will create are stored in the same folder as the
SimpleSat.exe program. It does nothing to the registry. It downloads sat
data from the net so use a computer connected to the net when you run the
program. I used Dreamweaver to create this beautiful web page.


Please respond off the board if you have information on my "width of swath"

tnx & 73 W9KE tom ...

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