A satellite is an object which has been placed into orbit by humans. Such objects are sometimes called artificial satellites to distinguish them from natural satellites such as the Moon. The first artificial satellite, Sputnik 1, was launched by the Soviet Union in 1957.

Since then, thousands of satellites have been launched into orbit around the Earth. They originate from more than 50 countries and have used the satellite launching capabilities of ten nations.

A few hundred satellites are currently operational, whereas thousands of unused satellites and satellite fragments orbit the Earth as space debris. A few space probes have been placed into orbit around other planets or bodies and become artificial satellites to the Moon, Venus, Mars, Jupiter and Saturn.

Satellites are said to be used for a large number of purposes. Common types include military and civilian Earth observation satellites, communications satellites, navigation satellites, weather satellites, and research satellites.

Mobile satellite systems help connect remote regions, vehicles, ships, people and aircraft to other parts of the world and/or other mobile or stationary communications units, in addition to serving as navigation systems.

Space stations and human spacecraft in orbit are also satellites. Satellite orbits vary greatly, depending on the purpose of the satellite, and are classified in a number of ways. Satellites are usually semi-independent computer-controlled systems.

The first United State’s satellite was also launched on January 31, 1958 and since then they have been monitoring the space and that currently they have tracked more than 8,000 man-made orbiting objects.

The rest have re-entered Earth’s atmosphere and disintegrated, or survived re-entry and impacted the Earth. The space objects now orbiting Earth range from satellites weighing several tons to pieces of spent rocket bodies. About seven percent of the space objects are said to be operational satellites.

These are some of the known satellites.
Anti-Satellite weapons/”Killer Satellites” are satellites that are armed, designed to take out enemy warheads, satellites, other space assets.

They may have particle weapons, energy weapons, kinetic weapons, nuclear and/or conventional missiles and/or a combination of these weapons.

Astronomical satellites are satellites used for observation of distant planets, galaxies, and other outer space objects.
Biosatellites are satellites designed to carry living organisms, generally for scientific experimentation.
Communications satellites are satellites stationed in space for the purpose of telecommunications.

Miniaturized satellites are satellites of unusually low weights and small sizes. New classifications are used to categorize these satellites as mini satellites (500–100 kg), micro satellites (below 100 kg) and nanosatellites (below 10 kg).

Navigational satellites are satellites which use radio signals transmitted to enable mobile receivers on the ground to determine their exact location. The relatively clear line of sight between the satellites and receivers on the ground, combined with ever-improving electronics, allows satellite navigation systems to measure location to accuracies on the order of a few meters in real time.

A photo space station where a lot research is going on both is space and on Earth Reconnaissance satellites are Earth observation satellite or communications satellite deployed for military or intelligence applications.

Very little is always mentioned about the full power of these satellites, as governments who operate them usually keep information regarding to their reconnaissance satellites classified.

Earth observation satellites are satellites intended for non-military uses such as environmental monitoring, meteorology, map making etc.

Space stations are man-made structures that are designed for human beings to live on in outer space. A space station is distinguished from other manned spacecraft by its lack of major propulsion or landing facilities instead, other spacecrafts are used as transport to and from the station.

Space stations are designed for medium-term living in orbit, for periods of weeks, months, or even years.
Weather satellites are primarily used to monitor Earth’s weather and climate changes.

When satellites reach the end of their mission, satellite operators have the option of de-orbiting the satellite, leaving the satellite in its current orbit or moving the satellite to what they call graveyard orbit.

Historically, due to budgetary constraints at the beginning of satellite missions, satellites were rarely designed to be de-orbited

Instead of being de-orbited, most satellites are either left in their current orbit or moved to a graveyard orbit.

As of 2002, it’s now a requirement that all geostationary satellites have to be moved to a graveyard orbit at the end of their operational life.

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