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Re: AW: Payload Birds Labeled

Hi Bob:

In regards to recent AMSAT-BB discussion of dualhopping between PCSAT and SAFIR-2, I have always been interested in the capablity to perdict when two satellites will be closest to each other on a particular orbit. (Keep in mind, when analyzing two polar orbiting satellites, they will always be closest to each other when over the North or South poles.)

I have some old DOS-based software called COLA (Collision Avoidance) that was written in 1992. Using COLA, you call up the orbital elements of one satellite, such as PCSAT, and run a set of other satellite orbital elements to see how close those satellites will come to PCSAT over a user-selected time period. 

Also, instead of analyzing how close a large number of satellites will come to your satellite, you can focus only on one satellite. Years ago I did this by performing an anlaysis on DO-17 and WO-18 where I found that over a three-year or so cycle they would get as close 0.10 kilometer of each other. (Of course, that is taking in account of the unknown error of using current Keplerian elements to forecast three years into the future. However, the beauty of a such a 3-year forecast is that eventually you can compare your perdiction to the most current Keplerian elements when the event actually occurs and as a result perhaps define that error.) However it was my intention that this analysis would be a good start for trying to identify key variables that would allow you to understand the orbital interrelationship/cycles of our four microsats that were released off of the same payload. Hopefully the results of all this would lead to a good Journal article (after Ken Ernandes, N2WWD reviewed my madness..hi). Unfortunately, other AMSAT duties have placed this little project on the backburner.

Anyway for the fun of it, yesterday I dug out COLA and ran some estimates for PCSAT and Rubin2. However, when comparing those COLA predictions to where  NOVA said they would be; they were no way close to each other. Inasmuch, I think long-forgotten Y2K may be effecting this software and perhaps giving me a prediction for 1903?. (Perhaps others on AMSAT-BB would be willing to open up COLA to anlayze and resolve and then perhaps repackage in a more improved format that could be housed on AMSAT-WWW?)

Anyway, while there appears to be no capability to crossband between these two satellites, other opportunities exist such as the SaudiSats and UO-14 who have a common uplink.
All the best in 2003 and 73,

Russ Tillman, K5NRK
Vicksburg, MS


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