In the relativistic theory for synchronization between satellite and ground atomic clocks, the major sources of relativistic effects are relative motion between the two clocks and the movement of clocks in a gravitational potential.
I am looking for the recent research and adapted clock correction models that have been modified on this topic as well as what are factors must be considered when comparing the proper/coordinate time of a clock at rest on the geoid and a clock in Earth orbit satellite?
By computing the invariant quantities. That's what ``synchronizing a clock'' means. Applying relativistic effects means storing and transmitting quantities that are invariant under Lorentz transformations. The way this is done in practice depends, of course, on the devices used, but the important thing to understand is that measurements are always local, therefore the only quantities that can be exchanged are invariants. If the rotation of the Earth is taken into account, then general relativistic effects must be taken into account, too. One way to do this is discussed here: Article Influence of relativistic effects on satellite-based clock s...
When they first sent up GPS satellites, they programmed them with what they believed to be the correct relativistic changes that would be needed which would affect time and GPS location determinations. They also installed a programmable system that can be reprogrammed from the ground, where they could upload any programmed changes when the satellite was overhead.
What they found was that the relativity program the system was originally given, was not accurate enough for GPS system calculations. They tried to correct these equations and the related program for a period of time but finally gave up. Instead, they uploaded a programmed algorithm that they believed could make the necessary corrections based upon information from the ground coming from one or more additional GPS satellites. The new system worked. So now all relativity corrections of GPS satellites are now based upon a self-correcting algorithm using new information from the ground and other GPS satellites on an ongoing basis.
Dear Prof. Stam Nicolis ,
Thank you very much for adding your answer
Regards
Dear Dr. Forrest Noble
Many thanks for adding your answer.
I think that if the current GPS satellites are based upon a self- relativistic correction in real-time. This is very good.
If you read about this topic, please post here.
Regards
Dear Abdelrahim Ruby,
Also thanks for your question. :) I wrote from what I had read many years ago when the first GPS system was being developed from the first two US satellites.
At that time, there were many praising the wonders of relativity theory. Engineers and scientists who built the system explained that relativity theory had nothing to do with the final system since they could not find any way to make the equations of special and general relativity work for the system after working on variations of these equations for a substantial amount of time.
Generally tossing relativity theory aside, they took the Engineers' approach and created a system of algorithms that did work when the information from at least two satellites was available and an atomic clock was on the ground.
For cell phone GPS systems, the GPS ground stations work with cell-phone
towers to determine the user's and destination's relative locations.
I can guess that other US satellites use the existing GPS system instead of trying to develop their own concerning variations of time in their orbits.
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