Name any two artificial satellite ?
Answers
Types of satellites
Navigation satellites
The GPS (global positioning system) is made up of 24 satellites that orbit at an altitude of 20,000 km above the surface of the Earth. The difference in time for signals received from four satellites is used to calculate the exact location of a GPS receiver on Earth.
Communication satellites
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.
Weather satellite orbits
Weather satellites operate in two orbit types. The GEO mode allows the same geographic area to be viewed continuously from a very high altitude. With the LEO polar orbit, complete Earth coverage is possible.
Weather satellites
These are used to image clouds and measure temperature and rainfall. Both geostationary and low Earth orbits are used depending on the type of weather satellite. Weather satellites are used to help with more accurate weather forecasting.
Earth observation satellites
These are used to photograph and image the Earth. Low Earth orbits are mainly used so that a more detailed image can be produced.
International Space Station (ISS)
The International Space Station (ISS) is a habitable artificial satellite that has been placed in a low Earth orbit. It completes 15.7 orbits per day and is maintained at an orbital altitude of between 330 km and 410 km.
Astronomical satellites
These are used to monitor and image space. A satellite such as the Hubble Space Telescope orbits at an altitude of 600 km and provides very sharp images of stars and distant galaxies. Other space telescopes include Spitzer and Chandra.
International Space Station (ISS)
This is a habitable space laboratory. At an altitude of 400 km, the ISS travels at a speed of 28,000 km/h and orbits the Earth once every 92 minutes. Scientists inside the ISS are able to perform many valuable experiments in a microgravity environment.
Satellite design
Every satellite has some of the same basic parts:
The bus – this is the frame and structure of the satellite to which all the other parts are attached.
A power source – most satellites have solar panels to generate electricity. Batteries store some of this energy for times that the satellite is in the shadow of the Earth.
Heat control system – satellites are exposed to extremely high temperatures due to exposure to the Sun. There needs to be a way to reflect and reradiate heat. Electrical components of the satellite can also produce a lot of heat.
Computer system – satellites need computers to control how they operate and also to monitor things like altitude, orientation and temperature.
Communication system – all satellites need to be able to send and receive data to ground stations on Earth or to other satellites. Curved satellite dishes are used as antennae
Attitude control system – this is the system that keeps a satellite pointed in the right direction. Gyroscopes and rocket thrusters are commonly used to change orientation. Light sensors are commonly used to determine what direction a satellite is pointing.
A propulsion system – a rocket engine on the satellite may be used to help place the satellite into the correct orbit. Once in orbit, satellites do not need any rockets to keep them moving. However, small rockets called thrusters are used if a satellite needs to change orbit slightly.
Parts of a satellite
Dr Allan McInnes describes the major components common to most satellites. He then explains how some of these function.
As well as these basic parts, satellites carry the equipment needed for their specific purpose.
Making space accessible
To get a satellite into space is a very expensive business that few can