Kurrent Keostationary Koordinates

[lude]

So, I noticed that when I have mysatellites at 2.863.334 metres my satellites shift their relative position to the KSC quite noticably over the course of a hundred days or so, did that change? 

What is the current geostationary distance? 

[RizzoTheRat]

Dunno but if you've got KER (or possibly MechJeb) installed you can get a readout of the orbital period and use that to tweak your orbit to a 6 hour period.

[FullMetalMachinist]

48 minutes ago, RizzoTheRat said:

Dunno but if you've got KER (or possibly MechJeb) installed you can get a readout of the orbital period and use that to tweak your orbit to a 6 hour period.

This, except for the "6 hours" part. The sidereal rotation period of Kerbin is 5h59m9.4s. If you put your sats at exactly 6hrs, they'll be off by almost a minute each orbit. That's a pretty substantial drift. 

[swjr-swis]

1 hour ago, lude said:

I noticed that when I have mysatellites at 2.863.334 metres my satellites shift their relative position to the KSC quite noticably over the course of a hundred days or so

KSO altitude didn't change (gravity and rotation period of Kerbin have remained the same), but the current version of KSP has a bit of an issue keeping orbits stable, which ends up affecting anything in KSO as well.

A stable craft with all engines and RCS deactivated in stable LKO will lose altitude at a rate of anything between a thousandth to a tenth of a meter per second. Watch the altitude display of Ap/Pe (Map view, or through KER/MJ) and you will notice this slow but steady decay.

This isn't supposed to happen and is a recent bug (although some might consider it a feature - yay, stock orbital decay and station keeping!).

Relevant link: http://bugs.kerbalspaceprogram.com/issues/9619

[lude]

Good to know :> thank you three.

Yeah currently it's kinda more of a feature to me^ now that I know that it didn't just change. @stock orbital decay

so is the bug that reverts circularized orbits on vessel change related to that? or was it even vessel change that triggered it?

[Alchemist]

It's not exactly 6 hours.

The period is 5h 59 min 9,425 s

the stationary altitude is 2863334 m

 

Yes, they fixed it so that 6 hours is period between two sunrises at the equator - the difference between the two values gives one rotation per year

Edited May 3, 2016 by Alchemist

[RizzoTheRat]

1 hour ago, FullMetalMachinist said:

The sidereal rotation period of Kerbin is 5h59m9.4s

Every day's a school day, I'd always assume it was 6 hours.

To be fair I've never put anything a keostationary orbit though, I just use that feature in KER to get constellations of RemoteTech KomSats to as close as possible period.

[Alchemist]

It was exactly 6 hours until a few versions ago. The stationary orbit was 2868 km then. Then they fixed it so that the day is exactly 6 hours now, not the rotation period.

[FullMetalMachinist]

47 minutes ago, RizzoTheRat said:

Every day's a school day, I'd always assume it was 6 hours.

Well that's the tricky thing, because it sort-of is.

One day on Kerbin's surface, from sunrise to sunrise, is exactly 6 hours. But in order for that to work, Kerbin has to spin just slightly more than 360 degrees, because during those 6 hours it moves along it's path around the sun. 

So the time that it takes to spin exactly 360 degrees (the sidereal rotation) is a little less, in this case 5h59m9.4s.