Empirical Earth · Test It Yourself

The satellite Doppler curve — an orbit you can hear

The claim

“A satellite’s Doppler shift only proves motion; a light swept across a dome would shift too.”

What is measured

A passing satellite slides from high pitch to low, crossing its rest frequency at the moment of closest approach. The width of that slide measures the speed. The steepness measures the height. The first satellite navigation system, Transit, turned this curve into a position fix good to tens of meters, and it did so by assuming Newton and a round Earth.

What would show this is wrong

a satellite whose signal holds a constant frequency across a full overhead pass, or a Doppler swing that does not scale with the transmit frequency, or a measured curve whose slope and width imply a speed and height that break Newton’s law of gravity. None has been recorded; Transit fixes rested on the opposite result.

Sources

  1. Transit and Doppler satellite navigation. The first satellite navigation system, Transit, deployed by the U.S. Navy in the 1960s, worked by measuring the Doppler shift of a satellite’s signa link
  2. Project Transit, U.S. Naval Institute Proceedings, May 1961. The contemporaneous account states the principle: a satellite is restricted by Newton’s laws, and of all permitted paths only one link
  3. Transit history and single-pass accuracy. Transit was declared operational in 1968 after five years of continuous use; once satellite orbits were well determined, two-dimensional position fi link
  4. Amateur satellite Doppler tracking. Operators working low-orbit amateur satellites and the space station correct for a Doppler swing of a few kilohertz on the 2-meter and 70-centimeter bands link
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