The ground track of a satellite is the line drawn on the Earth’s surface as the satellite passes overhead. This tool lets you control those tracks.
Often drawn in a map of the Earth, they are a common feature in satellite mission control rooms around the World.
Information on the size, shape and inclination of an orbit can be inferred directly from a ground track.
- The ground track does not exceed a latitude equal to the orbit inclination.
- An orbit with a period of less than (about) one day and of inclination <90 deg. will move from west to east.
- An orbit with a period greater than (about) one day and of inclination >90 deg. will move from east to west.
- An orbit with a period equal to (about) one day will appear stationary, this is called a geostationary orbit.
- A geostationary orbit has semi-major axis of 42 166.3 km
Due to variations in orbit eccentricity and/or inclination, it is possible for the ground track to crossover itself and for the motion to appear inverted.
View of Mercury Control Center during a simulation of the Mercury-Atlas 8 (MA-8) flight of the Sigma 7, 10 September 1962, showing satellite ground track on the wall.
This tool visualises the ground track of three satellites, and shows what they can see for a given field of view from the satellite as it looks towards Earth.
The tool uses a basic orbit simulator that accounts for the non-spherical nature of Earth, to the first order. The initial orbits show how we use so-called Molniya orbits to provide coverage of the polar regions with only two satellites, and a Sun-synchronous orbit of the type frequently use for Earth observation missions. Both of these orbits are special cases that exploit the non-spherical nature of Earth, but in very different ways.
Use the sliders to vary the satellite orbits and see how the ground track and coverage area changes.
You can read more Nibbles in Space at 
SpaceProf.xyz 
. And, if you want to go into more depth at The International Handbook of Space Technology which is a definitive modern text on space technology with contributions from globally leading agency experts from NASA, ESA, JAXA, and CNES, as well as European and North American academics and industrialists. This comprehensive handbook provides an overview and a holistic understanding of the system-of-systems that is a modern spacecraft.