Inclined geosynchronous orbit

[Eric Hedman]

I have never heard of any satellites in a circular orbit at geosynchronous height in anything other than the equatorial plane.  Has anyone ever tried putting a satellite in a circular orbit at that altitude highly inclined to the equator at 30 or more degrees?  Would it be stable so that it would appear from the ground beneath to move north and south over the same longitude in a 24 hour cycle?  Would it be useful for earth observations in such a pattern? I'm just curious.

[Galactic Penguin SST]

I have never heard of any satellites in a circular orbit at geosynchronous height in anything other than the equatorial plane.  Has anyone ever tried putting a satellite in a circular orbit at that altitude highly inclined to the equator at 30 or more degrees?  Would it be stable so that it would appear from the ground beneath to move north and south over the same longitude in a 24 hour cycle?  Would it be useful for earth observations in such a pattern? I'm just curious.

The Chinese Beidou Satellite Navigation System has a few geosynchronous satellites inclined 55 degrees from the Equator in operation. The Indian IRNSS also has a few in 30 degrees GSOs.

The Japanese Quasi-Zenith Satellite System (GPS enhancement region navigation system) has the majority of satellites in a similar, slightly elliptical (32600 x 38900 km), 40 degrees inclination orbit.

All are chosen to expand these regional navigation satellite systems to places further from the equator, which all 3 has true GEO satellites covering.

I don't think true I/GSO communication satellites have appeared yet, the closest are the old XM Radio/Sirius XM satellites (1-4) that were used in Tundra orbits, these have been or close to being replaced by GEO based ones.

[Eric Hedman]

Thanks.

[daedalus1]

Geosynchronous means 24 hour.
Geostationary means 24 hour at 0 degrees.

[Newton_V]

Titan IV had a high-inclined (~63 deg) 24-hr reference mission. 
I think a couple of the TDRS satellites are in 8 to 12 deg inclinations as well.

[DanClemmensen]

I have never heard of any satellites in a circular orbit at geosynchronous height in anything other than the equatorial plane.  Has anyone ever tried putting a satellite in a circular orbit at that altitude highly inclined to the equator at 30 or more degrees?  Would it be stable so that it would appear from the ground beneath to move north and south over the same longitude in a 24 hour cycle?  Would it be useful for earth observations in such a pattern? I'm just curious.

Some satellites are deliberately placed in GSO orbits that are not GEO, but even  GEO itself is not a stable orbit, so a satellite placed in GEO must perform station-keeping. As a GEO satellite ages the operator can extend its mission by conserving station-keeping fuel, by allowing the orbital inclination to increase from zero, these satellites are no longer in strict GEO orbits but they are still in GSO orbits. They move in a 24-hour "analemma" (figure 8 ) centered on their nominal GEO position as seen from the ground. The motion is not large enough to take the satellite out of the beam of the small fixed antennas used by GEO consumers, but the large teleport antennas and some large commercial customer antennas must move to track them.

[edkyle99]

I have never heard of any satellites in a circular orbit at geosynchronous height in anything other than the equatorial plane.  Has anyone ever tried putting a satellite in a circular orbit at that altitude highly inclined to the equator at 30 or more degrees?  Would it be stable so that it would appear from the ground beneath to move north and south over the same longitude in a 24 hour cycle?  Would it be useful for earth observations in such a pattern? I'm just curious.

Some satellites, military and civil, have used inclined geosynchronous orbits.  These satellites trace a "Figure-8" pattern above Earth every 24 hours above and below the equator along a line of longitude.   The length of the pattern is determined by the orbit inclination.

 - Ed Kyle

[AmigaClone]

I have never heard of any satellites in a circular orbit at geosynchronous height in anything other than the equatorial plane.  Has anyone ever tried putting a satellite in a circular orbit at that altitude highly inclined to the equator at 30 or more degrees?  Would it be stable so that it would appear from the ground beneath to move north and south over the same longitude in a 24 hour cycle?  Would it be useful for earth observations in such a pattern? I'm just curious.

Some satellites, military and civil, have used inclined geosynchronous orbits.  These satellites trace a "Figure-8" pattern above Earth every 24 hours above and below the equator along a line of longitude.   The length of the pattern is determined by the orbit inclination.

 - Ed Kyle

Note that if the inclined geosynchronous orbit is an ellipse instead of a circle, the "Figure-8" mentioned above would not be symmetrical when comparing the Northern and Southern portions of the above mentioned figure.

[edkyle99]

Note that if the inclined geosynchronous orbit is an ellipse instead of a circle, the "Figure-8" mentioned above would not be symmetrical when comparing the Northern and Southern portions of the above mentioned figure.

Yes.  Sirius being one example.  Designed to give better coverage of higher latitudes in the northern hemisphere I think.

 - Ed Kyle

[John Santos]

The first two satellites placed in geosynchronous orbit, Syncom 1 and 2, both launched in 1963, had orbits inclined by about 33 degrees.  Communications were lost with Syncom 1 (launched February 14, 1963) at geo insertion, but NASA published its orbit so they (or NORAD) must have picked it up with radar in geosync orbit.  Syncom 2, launched on July 26, was successful.
Next up was Syncom 3, launched a year later, which had an inclination of 6.5 degrees.  That might be close enough to count as geostationary.

[Eric Hedman]

Thanks for all the great information.  This is what I love about this site, lots of people who know tons about everything related to space.