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I think they actually have a separate time called OBT (maybe it stands for Orbit). I was at the Johnson Space Center in Houston recently, where we got a tour o
by clamprecht 9y ago
I think they actually have a separate time called OBT (maybe it stands for Orbit).
I was at the Johnson Space Center in Houston recently, where we got a tour of the live Mission Control room for the International Space Station. I noticed two clocks at the top of one of the screens. One was GMT, the other was "OBT", and the OBT clock was around 17 seconds ahead of GMT. I think it has to do with relativity, and the fact that the space station is moving relatively faster than the earth. Maybe someone can confirm.
I got a photo of this mission control monitor if anyone is interested.
- jharohit 9y agoIf you know the clock drift, won't you be able to calibrate the space station clock back to GMT+0, thus eliminating the need for an OBT?
- dannyw 9y agoGMT is already corrected back to earth GMT. But if you’re doing a time sensitive measurement and went to measure real seconds, you look at OBT.
- userbinator 9y ago+17s would not be due to time dilation, neither in magnitude nor sign; references I could find show that time on the ISS is slower than on Earth by around 14ms per year, and the ISS has been on orbit for less than 20 years.
- icegreentea2 9y agoOBT (I'm guessing onboard time actually), is probably using GPS time (https://en.wikipedia.org/wiki/Global_Positioning_System#Timekeeping https://en.wikipedia.org/wiki/Global_Positioning_System#Time...) which is now 18 seconds ahead of UTC due to additional leap seconds inserted into UTC since GPS time started.