Satellite

A satellite or an artificial satellite is an object, usually a spacecraft, placed into orbit around a celestial body. Satellites have many important jobs. They help with communication, weather forecasting, navigation through systems like GPS, broadcasting TV and radio, and doing scientific research. They also watch over the Earth.

Most satellites make their own electricity, often using solar panels. They carry special tools called transponders to talk to people on the ground. Many satellites are built using a standardized bus to save money. Some small satellites are called CubeSats. Satellites can work together in groups known as constellations.

The first artificial satellite ever launched was the Soviet Union's Sputnik 1 on October 4, 1957. Satellites help us in many ways every day, from checking the weather to finding our way with GPS.

History

See also: Timeline of first artificial satellites by country

The idea of satellites has been around for a long time. In 1687, Isaac Newton used an idea called "Newton's cannonball" to explain how natural satellites move. Later, in 1869, Edward Everett Hale wrote a story called "The Brick Moon" where a satellite was launched into orbit. In 1903, Konstantin Tsiolkovsky wrote about using rockets to launch spacecraft.

The first artificial satellite was Sputnik 1, launched by the Soviet Union in 1957. It helped scientists learn about Earth's atmosphere. This started the Space Race between the Soviet Union and the United States. The United States launched its first satellite, Explorer 1, in 1958. Since then, many countries have launched satellites for communication, weather forecasting, and science.

Components

Most satellites have special engines to stay in the right place in space. They also have parts that help them point in the correct direction. Close to Earth, satellites feel the pull of Earth's gravity and the Sun's energy, so they need to stay steady. Farther away, the pull of the Moon and Sun matters more.

Satellites get power from solar panels that turn sunlight into energy. When there is no sunlight, like inside a rocket or at night in space, they use batteries to keep working.

Applications

Main article: Communications satellite

Main article: Reconnaissance satellite

Main article: Space telescope

Main articles: Space weapon, Anti-satellite weapon, and Early warning satellite

Satellites have many important jobs. They watch Earth from space. This helps scientists learn about weather, natural disasters, and changes on our planet. They also help people talk to each other over long distances and help us find our way using tools like GPS.

Some satellites look at stars and other objects far away in space. Others carry out special experiments, like taking living things into space to learn more about them. Satellites help us learn about our universe and how things work in space.

Environmental impact

The environmental impact of satellites is growing as more are sent into space. Satellites and their launches use many resources and can pollute the atmosphere. For example, the metal aluminium, often used in satellites, can harm the environment because of how it is mined and processed.

Rocket launches release pollutants like black carbon and nitrogen oxides, which can damage the ozone layer. Satellites in space can also release chemicals and break down, adding more pollution. More satellites can make the night sky brighter, which might disturb animals that use stars to find their way. When satellites stop working, they often fall back to Earth, adding pollution to the air and oceans. Scientists are searching for ways to lessen these impacts, such as using wooden materials for satellites.

Main articles: Satellite observation, Space debris

Interference

Space debris poses dangers to satellites in orbit. It could make future space missions very difficult. More satellite constellations, like SpaceX Starlink, are being launched. They can interfere with astronomical research. Organizations like the IAU are working on ways to reduce these harmful effects.

Satellites can also face radio interference from land-based transmitters. This can disrupt their signals. It is especially a concern for GPS satellites, but it can affect satellite phone and television signals too. Sometimes, Earth stations accidentally send signals at the wrong time or frequency. Satellite operators use special tools to detect and manage these issues.

Regulation

As more satellites are sent into space, problems like space debris and light pollution are becoming bigger. But there are still not many rules to manage these problems at national or international levels.

Usually, responsibility for any problems caused is handled by the Liability Convention.

Operation

Operating satellites has become more varied and keeps growing. To run a satellite, you need money, factories to build it, rockets to launch it, and special equipment on the ground to control it. These tools help satellites do important jobs like talking to people far away, watching the weather, and guiding cars with GPS.

List

See also: List of heaviest spacecraft

This is a list of some heavy satellites that orbit Earth. It does not include space stations or spacecraft that go beyond Earth’s orbit. The list includes satellites located at a special point called the Sun-Earth Lagrange point 2.