Hello Geoff,

The doppler method was used in the early days of the space age, (and maybe still is). It's a neat bit of detective work. Monitor the frequency of the satellite, and determine the time of closest approach. From that you can determine the speed and altitude. Build up enough data points and you can figure out the orbit. Like you said, the target doesn't need to cooperate, just transmit.

As with the latest cubesat launch, when there are many objects, it takes several weeks to figure out who's who. This could be way around that problem.

73 Armando N8IGJ

Hi Armando et al,

I don't know about the methods written up by Karl & James. For a long time I've had a project using Doppler shift curves in the back of my mind (the "target" doesn't need to cooperate). I have most of the hardware based around my HPSDR box and a t'bolt frequency reference. The software hasn't even progressed beyond ideas and algorithms. I haven't even picked a language or development environment (one day).

I can see a very accurate Doppler shift curve being useful in the early days after a multiple cubesat launch. How accurate would you need to be to pick "your" cubesat from the crowd? One pass? multiple passes?

Anyway that's this morning's breakfast coffee ideas from me. Have fun y'all :-).

73 de Geoff vk2tfg (/3).