Definition of low Earth orbit

Photonics Dictionary

low Earth orbit: Low Earth orbit (LEO) refers to a region in space that is relatively close to Earth's surface, typically characterized by altitudes ranging from approximately 180 to 2,000 kilometers (112 to 1,242 miles). Satellites and spacecraft in low Earth orbit follow paths that are close to the planet, completing an orbit around Earth in a relatively short period.

Key characteristics of low Earth orbit include:

Altitude range: LEO extends from altitudes just above the Earth's atmosphere (around 180 kilometers) up to about 2,000 kilometers. This range is significantly closer to Earth compared to higher orbits like medium Earth orbit (MEO) and geostationary orbit (GEO).

Orbital period: Satellites in low Earth orbit have relatively short orbital periods, typically ranging from about 90 minutes to a few hours. The shorter orbital periods result from the closer proximity to Earth, causing faster orbital speeds.

Applications: LEO is a common orbit for various types of satellites and spacecraft, including Earth observation satellites, scientific research satellites, and many communication satellites, especially those involved in satellite constellations.

Space stations: Notable human-made structures in low Earth orbit include space stations, such as the International Space Station (ISS). These space stations serve as research laboratories and habitation modules for astronauts.

Rapid orbital decay: Satellites in low Earth orbit experience atmospheric drag, causing them to gradually lose altitude over time. Without periodic adjustments (reboosts), satellites in LEO may re-enter Earth's atmosphere and burn up.

Advantages: Low Earth orbit is advantageous for Earth observation and imaging satellites due to its proximity, resulting in higher spatial resolution for imagery. It is also favored for certain types of scientific experiments and missions due to the shorter communication delays.

LEO is a dynamic and frequently used region for space activities, hosting a variety of satellites and spacecraft for different purposes. The choice of orbit depends on the specific mission requirements and objectives of the spacecraft or satellite.