the ground station puts in the estimated Doppler, so all you're really tracking is the variation in the local oscillator).

My best case scenario for NTP jitter is about 0-5ms between a stratum 1 and a stratum 2 server directly connected via gigabit ethernet crossover (and the stratum 1 itself with a connected refclock seems to be at a baseline of 0-1ms most of the time, and rarely higher than 2ms) Those are just rough estimates based on casual observation, and I haven't done any

Produces a quite reasonable estimate of c. Other methods could be used to accurately know the wavelength of light. The other experiments to measure the gravitational constant G were equally interesting. The real reason for the interferometer was to try and detect the effect of the "aether" which light was supposedly propagated in.

So, I would do this: 1) Drop first 10 samples 2) Notch filter for removing sine noise 3) Estimate quadratic with least square, and remove 4) MADEV Notching out sine noise is not something I've seen in the literature, but I have tried it and it works really well as long as one care about unity gain.

estimate the center of the shadow, which could easily be done within 1/2". You now have your north direction. Solar noon is trivial to find out. The USNO Astronomical Applications page will give you a solar ephemeris for a specified lat/lon. or knowing your longitude and applying the equation of time, you can calculate when solar noon is.

This may be useful in improving estimates of this phase error due to limited timing resolution but doesnt remove the 1Hz sawtooth phase error that is present. Bruce

Another thing, the frequency detector phase history may need to be unwrapped prior to subtraction in order to make sure the frequency estimate becomes correct. > Turning on the "D" term in a PID with a prefilter is mostly not > recommended, They tend to just cancel each other.

stn=rach As a crude estimate, 1000CPM = 1mR/hr, or 1CPM = 1uR/hr. So I suspect the 60CPM received in Colorado is use to local radiation rather than cosmic rays. My Ludlum isn't calibrated, but I've compared it to one from the DOE using their source and it matched close enough for government work.

If both time and phase are very accurate, the resulting frequency estimate will be accurate as well. Some examples: Taking a PPS output and time stamping it to picoseconds is one way to do this. It is always a zero phase (rising edge for instance), so it drops back to a delta time measure.

I actually proposed to start in open-loop mode, estimate the frequency and then close the loop after a coarse frequency adjustment have been done. In closed loop, the beat-note shape, which comes from non-linear modulation, clearly indicates the direction. You can use this knowledge to learn the polarity, as one of many methods.