Hello everyone,

First, thank you to everyone for your patience with my questions. I have a new one - I tried searching the various threads here and didn't find anything that I think answered my question, so I'll pose it here.

During the de-chirping process, it sounds as if there are many, many different possible results, each with a different amount of Doppler shift. Is the goal of this process to find the one that results in (near) zero shift?

So for example, let's say the search frequency is 1420 MHz. The science team is receiving signals with Doppler, whose barycentric frequency (See? I'm getting just enough knowledge to be dangerous.) is 1420 MHz. It sounds like the goal of de-chirping is to see how much Doppler shift the signal is undergoing. If that's correct, what can be gained from having that information? Obviously the scientists would know where the antenna is pointing, and motion over time would, I'm guessing, tell us about how far out the signal is coming from.

Or am I completely lost? Thank you in advance.

Dave

Yes, the idea is that when doing narrow bandwidth signal searches as SaH v7 does, we need to compensate for any change in frequency caused by doppler effects. That is, if we're checking at a bandwidth of 0.596 Hz. and the signal frequency is changing at 1 Hz. per second there wouldn't be enough signal to characterize without dechirping. If we dechirp at something near 1 Hz. per second the signal remains within the analysis bandwidth long enough.

The weak signals we're trying to pull out of the noise typically only show at one specific chirp rate, and that rate may provide a clue to where a transmission is originating. Transmission from a planetary surface can be expected to have relatively low doppler, from orbit around a planet more, orbit around a neutron star could be a lot.

                                                                   Joe

Believe it or not, I actually understand that. ; )

I'm constantly amazed at the precision and sensitivity of these pieces of equipment.