> So clocks on the ISS, for example, tick slower than Earth clocks; but clocks on the GPS satellites (orbiting at 4.2 Earth radii) tick faster (and there is an adjustment made for this on each satellite so that the time signals they send out match Earth clock rates)
replyI'm curious, and hope you or somebody else might be able to answer this: is it a single adjustment for each thing, where they just set it to always adjust by X ratio, or does it vary (enough to matter) as it orbits, such that the adjustment needs to be constantly varying slightly?
The exact difference in clock rates is not constant, because the orbits are not perfectly circular and the Earth is not a perfect sphere. So both the altitude and speed of the satellite, and the Earth's gravitational potential, are varying with time, and that means the clock adjustments will vary with time as well.
replyFor the GPS satellites, their time signals are constantly compared with ground clocks, and adjustment signals are sent up to the satellites as needed to keep their clock corrections in sync with ground clocks.
I'm not sure what, if any, adjustments are made to clocks on the ISS, or how they're done.
Thanks! I figured the orbital paths not being exact circles meant they'd be slight variance in the difference, just wasn't sure if it was enough to matter or if they could treat it as if it was exactly the same all the way around without it mattering.
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