A propulsion system – a rocket engine on the satellite may be used to help place the satellite into the correct orbit.Light sensors are commonly used to determine what direction a satellite is pointing. Gyroscopes and rocket thrusters are commonly used to change orientation. Attitude control system – this is the system that keeps a satellite pointed in the right direction.Curved satellite dishes are used as antennae Communication system – all satellites need to be able to send and receive data to ground stations on Earth or to other satellites.Computer system – satellites need computers to control how they operate and also to monitor things like altitude, orientation and temperature.Electrical components of the satellite can also produce a lot of heat. There needs to be a way to reflect and reradiate heat. Heat control system – satellites are exposed to extremely high temperatures due to exposure to the Sun.Batteries store some of this energy for times that the satellite is in the shadow of the Earth. A power source – most satellites have solar panels to generate electricity.The bus – this is the frame and structure of the satellite to which all the other parts are attached.Weather satellites are used to help with more accurate weather forecasting.Įvery satellite has some of the same basic parts: Both geostationary and low Earth orbits are used depending on the type of weather satellite. These are used to image clouds and measure temperature and rainfall. These are used for television, phone or internet transmissions, for example, the Optus D1 satellite is in a geostationary orbit above the equator and has a coverage footprint to provide signals to all of Australia and New Zealand. The difference in time for signals received from four satellites is used to calculate the exact location of a GPS receiver on Earth. The GPS (global positioning system) is made up of a minimum of 24 satellites (and allows for up to 32), that orbit at an altitude of 20,000 km above the surface of the Earth. The altitude chosen for a satellite depends on the job it is designed for. This is used for many communications and weather satellites. This is to match the rotation of the Earth so that the satellite appears to stay above the same point above the Earth’s surface. Geostationary orbit (GEO) – 36,000 km above the Earth.Medium Earth orbit (MEO) – most MEO satellites are at an altitude of 20,000 km, and time for one orbit is 12 hours.Low Earth orbit (LEO) – from 200 to 2,000 km, for example, the ISS orbits at 400 km with a speed of 28,000 km/hour, and time for one orbit is about 90 minutes. The main part of this is as big as a large five-bedroom house, but including solar panels, it is as large as a rugby field.Īltitudes of satellites above the Earth’s surface also vary. The largest artificial satellite is the International Space Station (ISS). Some communication satellites are about 7 m long and have solar panels that extend another 50 m. Some cube satellites are as small as 10 cm.
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