Understanding the difference between Geostationary Transfer Orbit (GTO) and Geostationary Orbit (GEO) is key to appreciating how satellites get to their final positions in space. These two types of orbits play crucial roles in satellite launches and operations. In this short article, we’ll break down what GTO and GEO are, how they differ, and why both are important for modern satellite technology.
The short answer is: GTO is a transfer orbit, elliptical and inclined, used to reach the circular, equatorial GEO, where satellites remain fixed relative to Earth. GTO is like a stepping stone, while GEO is the satellite’s final destination for operation.
Put differently, GTO acts as a temporary path that helps satellites reach GEO, where they can stay fixed above a specific point on Earth’s surface. The longer answer is below!
Geostationary Transfer Orbit (GTO)
GTO is an elliptical orbit used as an intermediate step to reach Geostationary Orbit (GEO). Spacecraft are launched into GTO first and then use onboard propulsion to transition to GEO.
GTO has a highly elliptical shape, with its perigee (closest point to Earth) typically around 200–300 km and its apogee (farthest point) near the geostationary altitude of 35,786 km. The inclination (tilt) is also higher than GEO.
This orbit is a cost-efficient way to launch satellites, as the rocket provides most of the energy to reach the elliptical orbit, and the satellite uses its own propulsion system to circularize the orbit at GEO.
Examples of Spacecraft Sent to GTO
INSAT-3DR: A weather and disaster monitoring satellite launched by India’s ISRO. It was initially placed in GTO before using its onboard propulsion to reach GEO.
Intelsat 37e: A communication satellite launched by an Ariane 5 rocket. It entered GTO as a transitional orbit before moving to its operational geostationary position.
Geostationary Orbit (GEO)
GEO is the final, operational orbit for many communication, weather, and broadcasting satellites. In this orbit, a satellite appears stationary relative to a point on Earth’s surface.
It is a circular orbit at a constant altitude of 35,786 km above Earth’s equator. The orbit is equatorial 🔗 and has zero inclination.
Satellites in GEO provide continuous coverage of specific areas on Earth, making it ideal for services like television broadcasting, weather monitoring, and telecommunications.
Examples of Spacecraft Sent to GEO
GOES-16 (Geostationary Operational Environmental Satellite): Operated by NOAA, it provides weather forecasting and environmental monitoring directly from GEO.
EchoStar 19: A high-capacity broadband satellite in GEO, used to deliver internet services to North America.
About Low Earth Orbit (LEO)
Low Earth Orbit (LEO) is a region of space close to Earth where most satellites, spacecraft, and the International Space Station (ISS) operate. It extends from approximately 160 km (100 miles) to 2,000 km (1,200 miles) above the Earth’s surface, making it the closest and most accessible orbit for many types of missions.
- Proximity to Earth: Being relatively close to the surface, objects in LEO experience less travel time and require less energy to reach compared to higher orbits.
- Orbital Period: Satellites in LEO typically complete an orbit in 90 to 120 minutes, depending on their altitude.
- Atmospheric Drag: The thin outer layers of Earth’s atmosphere are still present in LEO, causing gradual orbital decay. Satellites in this orbit require occasional adjustments to maintain their position.
Uses of LEO
Communication and Internet Satellites:
LEO is ideal for low-latency communication, used by constellations like Starlink and OneWeb for global broadband services.Earth Observation:
Satellites in LEO can capture high-resolution images for weather forecasting, environmental monitoring, and military reconnaissance.Human Spaceflight:
The International Space Station (ISS) orbits in LEO, along with spacecraft like SpaceX’s Crew Dragon and Soyuz that ferry astronauts to and from the ISS.Scientific Research:
LEO is used for microgravity experiments and space telescopes like Hubble, which benefit from a clear view of space without being too far from Earth.
