B Time Dilation Effect: Corrections to Clocks on ISS

[saddlestone-man]

TL;DR Summary

How often are corrections applied to clocks aboard the ISS to synchronise them to clocks on Earth?

Hello All

The Hafele-Keating experiment in 1971 confirmed measurable time dilation effects on atomic clocks flown around the Earth on aircraft.

Presumably clocks aboard the International Space Station suffer worse time dilation because of their greater speed in orbit. How often are corrections applied to clocks aboard the ISS to keep them synchronised to clocks on Earth?

best regards ... Stef

 

[Bandersnatch]

The nett time difference on ISS is on the order of 1 second per lifetime. Hardly a need to worry about outside high precision measurements.

 

[russ_watters]

GPS on the other hand...

 

[Orodruin]

Note however that GPS satellite clocks run faster than a clock on the Earth since the gravitational time dilation effect is larger than the one due to the velocity. For the ISS orbit we are still in a low enough orbit for the velocity effect to dominate.

 

[saddlestone-man]

The nett time difference on ISS is on the order of 1 second per lifetime. Hardly a need to worry about outside high precision measurements.

The question is therefore are there any high precision measurements going on on board ISS and how often are corrections made so that these measurements are valid?

 

[Ibix]

The question is therefore are there any high precision measurements going on on board ISS

Not quite. The clocks in the ISS work perfectly normally and no correction is needed. You only have problems if you are doing experiments with one component in the ISS and another on Earth or in a different vehicle, in which case the clocks at the two locations might tick at different rates. That's why the GPS clocks are slightly adjusted, because part of the service includes receivers on Earth and we need precise time in the Earth time system not the satellite one.

The only types of experiment I can think of that would require enough precision to be affected by gravitational time dilation are ones to test time dilation, where of course you don't adjust the clocks because their mismatch is the point. I could be wrong - I don't know what experiments they're running. But the degree of time dilation is so slight that it would be something very rare indeed that would care.