How High Are Satellites?

There are so many man-made satellites out there, it’s around 2666 satellites (UCS, 1 Apr ’20). But have you ever wondered how high are satellites? Let’s discuss this.

satellite

To find the altitude of a satellite, we must know it based on the types of satellite orbits out there.

Types of Satellite Orbit

Satellites have various orbits, this of course depends on the purpose of the satellite. In this article, we will discuss satellites that are orbit the Earth, not those directed out like to orbit Mars or Jupiter etc.

Geostationary Orbit (Geostationary Orbit (GEO))

This orbit has an altitude of 35,786 km. It has the same orbital period as the rotation period of the earth, which is 23 hours 56 minutes 4 seconds. This makes the satellites in this orbit stationary or remains above the earth’s surface below. This type of satellite is always above the equator. This orbit is generally used by satellites which must always be above certain areas, such as communication satellites, weather monitoring satellites, and navigation satellites. One example is Indonesia’s satellite, the Palapa satellite.

geostationary orbit
Copyright: ESA – L. Boldt-Christmas

Low Earth Orbit (LEO)

This orbit has an altitude from 160 km to 1000 km. As the name implies, this orbit is relatively low compared to other types of orbits. Even so, this altitude is actually still very high when compared to the height of commercial aircraft which are generally under 12 km. Unlike satellites at GEO, these types of satellites do not have to be at the equator or can have a tilted orbit, as in the following figure.

low earth orbit
Copyright: ESA–L. Boldt-Christmas

This orbit is generally used by satellites which must be close to the surface of the Earth. For example, the satellite used for Google Maps, of course, to get a good picture of the earth’s surface this satellite must be placed on LEO. Two of all satellites used for Google Maps are Landsat 1 and Landsat 8, each of which has an altitude of 917 km and 705 km. Besides, ISS (International Space Station) also orbits in low orbits like this, this certainly makes it easier for astronauts to commute from the space station.

Even though it is close to the surface of the Earth, such low orbits are not quite right when used for communication satellites. This happens because these types of satellites move very fast in the sky and communication stations on the land themselves need time to be able to track/connect to communication satellites in orbit.

Even so, there are also communication satellites in this low orbit which are generally in the form of satellite constellations. Satellite constellations are groups of satellites that are coordinated in specific orbits. Satellite constellations can make wider and constant coverage of the Earth’s surface.

Medium Earth Orbit (MEO)

Earth’s orbit is having a very wide height range, which is between LEO and GEO. So, the satellites in this orbit have altitudes above 1000 km and below 35,768 km.

This type of orbit is used by various types of satellites with various purposes, such as navigation, communication, geodetic, and experimental. One of them is the constellation of satellites used for GPS. Satellites for GPS consist of 31 satellites at an altitude of 20,180 km.

Another example is the Galileo satellite constellation. This satellite constellation serves navigation communications in Europe and is used for a variety of navigation, from commercial aircraft navigation to navigation on smartphones.

Orbit Transfer or Geostationary Transfer Orbit (GTO)

Transfer orbit or geostationary transfer orbit is a special type of orbit that only occurs in certain cases. Generally, this type of orbit applies when there is an orbit shift or when the satellite is first launched. This GTO aims to move satellite locations with minimal energy consumption.

When launched, the satellite is certainly not directly in its orbit, certainly initially near the surface of the earth or in LEO. If we want to put satellites on GEO, we can adjust the satellite’s trajectory as shown below.

geotransfer orbit
GEO (red circle) dan GTO (blue elips)
CopyrightL ESA – L. Boldt-Christmas

Conclusion

So, how high are satellites? Satellites have various orbits thus have various altitude depending on the purpose of the satellite. GPS satellites are at MEO, which means that they are at an altitude between 1000 km and 35,786 km, more precisely at an altitude of 20,180 km. While the Palapa-D satellite owned by Indonesia is in GEO, which means it has an altitude of around 35,786 km.

orbit satelit
Satellite orbit comparison
Copyright: cmglee

You can try the interactive satellite orbit version of the following satellite.

Satellite Orbit Comparison

Sources and References:

  1. Types of Orbits – ESA
  2. UCS Satellite Database – Union of Concerned Scientist
  3. Here’s How High Planes Actually Fly, According to Experts – Time
  4. Landsat 1 – USGS
  5. Landsat 8 – USGS
  6. Iridium Satellites – N2YO
  7. Medium Earth Orbit – Wikipedia

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