Synchronous orbit
A stationary orbit is an orbit with the same orbital period as the rotational period of the orbited body. The eccentricity is equal to 0 and the inclination is exactly 0°. A satellite on this orbit will stay in the sky at the same position at all times, the surface velocity is zero and making the communication easy as the ground based telescopes don't have to follow the satellite's relative motion.
A stationary orbit is a special kind of synchronous orbit, which all have the same orbital period but may differ in inclination or eccentricity. Satellites on a synchronous but not stationary orbit have a ground track forming an analemma. Because it is impossible to get all values exact for a stationary orbit, every satellite on a synchronous orbit form an analemma.
Some celestial bodies don't allow synchronous orbits, and thus also no stationary orbits, because the altitude lies outside the celestial bodies' sphere of influence. This is because of a very slow rotation requiring a very high altitude to allow such long orbital periods explaining why all tidally locked moons don't have a synchronous orbits. Moho is the only planet without any synchronous orbit, because it's very slow rotational period with only almost two rotations in one orbit.
Altitudes
The following table, contain the altitudes for a circular synchronous orbit around all celestial bodies, even when the altitude resides outside the SoI. The altitudes are from the body's surface, while the semi-major axes are from the body's center.
| Body | Synchronous orbit | Semi-synchronous orbit | |||
|---|---|---|---|---|---|
| Altitude | Semi-major axis | Altitude | Semi-major axis | ||
| Kerbol | 1 508 045.29 km | 1 769 645.29 km | 853 206.67 km | 1 114 806.67 km | – |
| Moho | 18 173.17 km † | 18 423.17 km † | 11 355.87 km † | 11 605.87 km † | No |
| Eve | 10 328.47 km | 11 028.47 km | 6 247.50 km | 6 947.50 km | No |
| Gilly | 42.14 km | 55.14 km | 21.73 km | 34.73 km | No |
| Kerbin | 2 863.33 km | 3 463.33 km | 1 581.76 km | 2 181.76 km | No |
| Mun | 2 970.56 km † | 3 170.56 km † | 1 797.33 km | 1 997.33 km | Yes |
| Minmus | 357.94 km | 417.94 km | 203.29 km | 263.29 km | No |
| Duna | 2 880.00 km ‡ | 3 200.00 km | 1 695.87 km | 2 015.87 km | No |
| Ike | 1 133.90 km † | 1 263.90 km † | 666.20 km | 796.20 km | Yes |
| Dres | 732.24 km | 870.24 km | 410.22 km | 548.22 km | No |
| Jool | 15 010.46 km | 21 010.46 km | 7 235.76 km | 13 235.76 km | No |
| Laythe | 4 686.32 km † | 5 186.32 km † | 2 767.18 km | 3 267.18 km | Yes |
| Vall | 3 593.20 km † | 3 893.20 km † | 2 152.56 km † | 2 452.56 km † | Yes |
| Tylo | 14 157.88 km † | 14 757.88 km † | 8 696.88 km | 9 296.88 km | Yes |
| Bop | 2 588.17 km † | 2 653.17 km † | 1 606.39 km † | 1 671.39 km † | Yes |
| Pol | 2 415.08 km † | 2 459.08 km † | 1 505.12 km † | 1 549.12 km † | Yes |
| Eeloo | 683.69 km | 893.69 km | 352.99 km | 562.99 km | No |
- † indicates that the altitude resides outside the SOI
- ‡ indicates that the altitude is the same as the orbit of another object
Sun-synchronous orbit
- → See also: Sun-synchronous orbit on Wikipedia
In the real world exists a sun-synchronous orbit, which isn't like a synchronous orbit around the Sun. Instead it describes an orbit around Earth which itself rotates, so it looks like the orbit stays the same relative to the Sun. As it requires an uneven gravitational field it is impossible to simulate in KSP.
See also
- KEO, the stationary orbit around Kerbin
- Geosynchronous Orbit (Math), some math on how to calculate a synchronous orbit
- Synchronous orbit on Wikipedia
- Synchronous orbit on Wikipedia
- Geostationary orbit on Wikipedia
- Geosynchronous orbit on Wikipedia
- Heights for (semi-) synchronous orbits on the KSP forums; Includes a formula for calculating (semi)synchronous orbits
