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9.4 Information systems 4. Geostationary satellites
Syllabus reference (October 2002 version) |
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| 4. Geostationary satellites relay and transmit information from the other side of the world | Students learn to: |
Students: |
Extract from Senior Science Stage 6 Syllabus (Amended October 2002). Board of Studies, NSW.
[Edit: 1 June 10]
Prior learning: Science Stages 4–5 syllabus, Outcome 4.6 (content 4.6.10: gravitational force).
gather, process and analyse information from secondary sources to identify the satellites used for ‘live’ telecast from other regions of the world to Australia and vice versa and to present reasons why communication satellites have different aerials and positional orbits
- Information can be gathered from various sources, such as the
Internet, books and CD-ROMs dealing with space and communication technologies.
- Satellite
orbits
Entertainment: Television, Ezilon Infobase, Community News and
Articles. This article isn't specifically about Australia but talks generally
about satellite communication and orbits of the satellites - A particularly relevant chapter on satellite communication is published in Space Australia, the story of Australia’s involvement in space by Kerrie Dougherty and Matthew James from the Powerhouse Museum, Sydney.
- Optus B, Australia's Second National Satellite System Boeing, Los Angeles,
California, USA
This site is more about Australia's telecommunications within Australia than with the rest of the world but it has some excellent information about it's launch, specifications and functions. - Australia begins new climate change satellite program By William Atkins
Tuesday, 16 March 2010, iTWire
- Satellite
orbits
- Process information by producing a list of satellites used by Australia for sending and receiving live broadcasts.
- Analyse all the gathered information to identify the satellites used for communication and present information about their positional orbit (e.g. low earth orbit satellites) and the types of aerials used (including frequencies) by each satellite and why they differ.
explain why an Earth-based satellite dish must always face the geostationary satellite communicating with it
- A geostationary satellite is one that orbits the Earth at the same period as the period of rotation of the Earth,( that is approximately every 24 hours) so that its position in the sky relative to any position on Earth is always the same. It must be in an equatorial orbit.
- The receiving dish on earth must be large as the signal is relatively weak, due to the satellite dish being quite distant at approximately 36,000 km. The satellite dish must face the same direction at all times to ensure that signals are received and retransmitted in the correct directions to the intended receivers.
explain why the satellite must be at a height where its revolution period is the same as that of the Earth’s period of rotation
- In order for a satellite to remain in orbit over the same point on the Earth’s surface at all times, it must be located 36 000 kilometres above the equator. In this orbit, the satellite travels at a speed that keeps it in the same position relative to the Earth’s surface and so the signal can be sent directly to and from the dish antenna on the Earth to the satellite.
- The Earth’s gravitational pull keeps the satellite in orbit. Satellites don’t fall towards the Earth because of their tremendous speed. Although they are pulled towards the Earth by gravity, their speed enables them to keep falling over the horizon. Thus, if they are travelling with exactly the correct speed they never actually get any closer to the Earth’s surface. Tracking stations on Earth use radio signals to activate small rockets on the satellite to keep them in the correct orbit.
An activity: Why do
satellites stay in orbit?
Gulf of Maine Aquarium, USA
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