Meaning
It is a type of geosynchronous orbit in which the satellite has an orbital period equal to the Earth’s rotation period, but the orbit is inclined with respect to the equator. Because of this inclination, the satellite does not appear fixed over one point on Earth.
Instead, from the ground, it appears to move in a figure-eight pattern over the same general region.
Main features
• Orbital period is about 24 hours
• Orbit is geosynchronous, but not geostationary
• Orbit is inclined to the equatorial plane
• Satellite appears to move north and south relative to the equator
• Ground track generally forms an analemma, or figure-eight shape
Difference from GEO
• GEO is a special orbit where the satellite is circular, equatorial, and appears stationary over one point
• IGSO has the same orbital period as Earth’s rotation but is inclined, so the satellite does not remain fixed at one point
So:
• GEO = fixed over one point
• IGSO = appears to oscillate in a figure-eight path
Why it is useful
IGSO is useful when a country wants stronger and repeated coverage over a particular region without relying only on geostationary satellites. It helps improve regional navigation and communication coverage.
For example, in NavIC, some satellites are placed in inclined geosynchronous orbit to improve regional coverage over India and surrounding areas. Every IGSO is geosynchronous, but it is not geostationary because of orbital inclination.
Conclusion
IGSO, or Inclined Geosynchronous Orbit, is a geosynchronous orbit with orbital inclination, in which the satellite matches Earth’s rotational period but appears to move in a figure-eight pattern instead of remaining fixed over one point.
