Understanding GTO
How a satellite climbs from GTO to GEO
Once the launch vehicle releases the payload into GTO, the satellite coasts out to apogee at 35,786 km. There it fires its own engine to raise the perigee and circularise the orbit — the burn traditionally delivered by a dedicated apogee kick motor. Because the orbit becomes truly circular only after the apogee burn (and any inclination correction) is complete, operators usually spread the work over several passes. Chemical propulsion can reach GEO within days, but many modern platforms now use electric propulsion for this orbit raising. Ion thrusters take weeks or months to spiral up, yet their high efficiency slashes propellant mass and frees weight for more payload.
Why launch-site latitude drives the fuel bill
A satellite launched due east inherits an orbital inclination equal to its launch site's latitude, so the transfer orbit is tilted relative to the equator. Reaching true GEO means removing that tilt, and the cheapest place to do it is at apogee, where the satellite travels slowest. Launch sites near the equator are therefore prized: from Europe's spaceport at Kourou (about 5°N) the combined circularisation-and-plane-change burn is roughly 1.5 km/s, whereas from Cape Canaveral (28.5°N) it rises to about 1.8 km/s. That difference directly reduces the mass a rocket can send to GEO.
Standard, subsynchronous and supersynchronous GTO
Not every GTO targets exactly GEO altitude. Launch providers tune the apogee to balance the work between the rocket and the satellite, giving three broad variants:
| GTO type | Apogee | Trade-off |
|---|---|---|
| Standard | ≈35,786 km (GEO) | Balanced share of delta-v between launcher and satellite |
| Subsynchronous | Below GEO | Rocket does less; the satellite must supply more delta-v |
| Supersynchronous | Above GEO | Higher, slower apogee makes the plane change cheaper; the apogee is later lowered back to GEO |