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.

http://www.tomdoyle.org/simplesat/simplesat.html

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

tnx & 73 W9KE tom ...