But naturally I'm just a "NASA shill" so what I say can be ignored.
Or an alleged engineer, a phrase he uses to describe Jay.
I recently took my master's diploma to my auto insurance company. They grant discounts to certain professionals, including electrical engineers. It seemed to convince them, so I guess I really am an electrical engineer.
Would there have been measurable Doppler shift from the signals received at Jodrell Bank, and is so, did the scientists measure the shift to confirm the landings as advertised?
Sure, and very easily.
Apollo communicated with earth with S-band radio signals with a wavelength of about 13 centimeters. A 13-cm change in distance between transmitter and receiver (the
range) therefore causes the phase of the received signal to rotate through a complete cycle of 360 degrees. A velocity along the same line (
range-rate) of 13 cm/s will shift the signal by 1 Hz: down if the distance is increasing, up if it's decreasing.
13 cm is pretty short compared to the earth-moon distance, but your ability to detect this relies on having very stable oscillators in both the receiver and the transmitter. This is somewhat difficult to do in a spacecraft, especially one that has to withstand lots of acceleration and vibration, but it's now done fairly often especially on interplanetary probes (e.g., New Horizons).
There's a simpler way when tracking a probe close enough to earth that noise and propagation delay aren't serious problems: with a
coherent transponder. To work around the need for an ultra-stable oscillator on the spacecraft, it locks onto the uplink signal from the ground, multiplies its frequency by a specific ratio, and sets its downlink transmitter to that frequency. For Apollo, and every other spacecraft using the same S-band range, this ratio is exactly 240/221. Now you can keep your ultra-stable oscillator on the ground, and even if it changes it will affect the uplink and downlink frequencies by almost the same amount. Note that now you'll see a full 360-degree rotation for each
half-wavelength change in range.
This is obviously simplest when the same ground antenna is both the uplink and downlink; this is
2-way coherent tracking. During the Apollo 11 landing, this was done by the Goldstone site in California. Jodrell Bank was simply listening in, making it a 3-way path, so their observation of Apollo's downlink signal would have been affected by all these things:
Frequency errors or drift between the reference oscillators at Goldstone and at Jodrell Bank. (I don't know what they each had, but atomic clocks were already fairly common and I suspect both sites were equipped with them).
The relative motions of the two stations along the earth-moon line caused by the rotation of the earth and moon and the orbital motion of the moon around the earth.
The position and motion of Eagle relative to the lunar surface.
The effect of parallax between the two stations as they viewed Eagle.
Nowadays it wouldn't be hard for a 3rd party site like Jodrell Bank to correct for all these effects and determine Eagle's absolute velocity with respect to the lunar surface, but I suspect they weren't doing this at the time. That explains why they still saw a continuing change in frequency after Eagle landed but one that was abruptly different from what it was during Eagle's descent.