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Earth observations satellites provide information for research subjects that benefit from looking at Earth’s surface from above (such as meteorology, oceanography, terrestrial ecology, glaciology, atmospheric science, hydrology, geology, and many more). Types of sensors on these satellites include passive and active remote sensors.
By 2021, that total had grown to over 950, with the largest number of satellites operated by US-based company Planet Labs. [4] Most Earth observation satellites carry instruments that should be operated at a relatively low altitude. Most orbit at altitudes above 500 to 600 kilometers (310 to 370 mi).
Clickable image, highlighting medium altitude orbits around Earth, [a] from Low Earth to the lowest High Earth orbit (geostationary orbit and its graveyard orbit, at one ninth of the Moon's orbital distance), [b] with the Van Allen radiation belts and the Earth to scale To-scale diagram of low, medium, and high Earth orbits Space of Medium Earth orbits (MEO) as pink area, with Earth and the ...
Satellites in geostationary orbit must all occupy a single ring above the equator. The requirement to space these satellites apart, to avoid harmful radio-frequency interference during operations, means that there are a limited number of orbital slots available, and thus only a limited number of satellites can be operated in geostationary orbit.
This is a list of satellites in geosynchronous orbit (GSO). These satellites are commonly used for communication purposes, such as radio and television networks, back-haul, and direct broadcast. Traditional global navigation systems do not use geosynchronous satellites, but some SBAS navigation satellites do.
Samples of three GPS satellites' orbits over a five-year period (2013 to 2018) USA-242 · USA-239 · USA-151 · Earth As of 22 January 2025, 83 Global Positioning System navigation satellites have been built: 31 are launched and operational, 3 are in reserve or testing, 43 are retired, 2 were lost during launch, and 1 prototype was never launched. 3 Block III satellites have completed ...
In addition, satellites in HEO can provide a continuous coverage of the Earth's surface, making it very useful for communication and navigation purposes. [5] A variety of satellites, such as TESS, [6] have been placed in HEO. There are four main reasons that most satellite are placed in lower orbits. First, a HEO can take a month or more per orbit.
A medium Earth orbit is a satellite in orbit somewhere between 2,000 and 35,786 kilometres (1,243 and 22,236 mi) above the Earth's surface. MEO satellites are similar to LEO satellites in functionality. MEO satellites are visible for much longer periods of time than LEO satellites, usually between 2 and 8 hours.