Satellite Communications

1. Satellite Communications

2. Learning Objectives: At the end of this topic you should be able to: • describe satellite communications, • give examples of typical applications of satellite communications. • explain the advantages and disadvantages of satellite communications,

3. What is a Satellite? Meteosat weather satellite Weight: 2000kg

4. What is a Satellite?

5. What is a Satellite?

6. What is a Satellite?

7. What is a Satellite? • a satellite is any object that revolves around a planet • there are many manmade (artificial) satellites, • ~13,000 satellites are tracked in real time • some are inactive, some are debris from space missions … • the path a satellite follows is called an orbit, • to access a satellite requires ‘line of sight’ communication • the receiver (satellite dish) must be in the satellite’s ‘footprint’ • most satellites are custom built to perform a function.

8. What are satellites used for? • television broadcasting • satellite TV (e.g. Sky) • telephone communications, • satellite ‘phones (e.g. “Iridium”) • weather forecasting, • satellite images (visible, infra red, radar) • Internet communications, • scientific research, • climate monitoring, global disaster monitoring, …. • Global Positioning System • GPS satellite navigation (‘SatNav’) • satellite tracking, security

9. How does Satellite Communications work? Generally: • there is a transmitter on the ground • the transmitter sends signals to a satellite • using microwaves • signal is received & amplified by the satellite • signal is retransmitted back to Earth • signal reaches its recipient • or is 'bounced back' to another satellite

10. Satellite Footprint

11. Satellite Launch

12. Satellite Launch

13. Satellite Separation

14. Satellite Deployment

15. GCHQ Satellite Ground station

16. BSkyB Satellite Groundstation

17. Where are these satellites? There are 2 main types of satellite orbit: • Geostationary orbit • always positioned over the same spot on Earth • orbit at 22,000 miles (36,000 km) • Low Earth Orbit (LEO) • orbit at 400-800km

18. Geostationary orbit

19. Geostationary Satellite • always positioned over the same spot on Earth • orbits at the same rotational speed as the Earth • approx 10,000 km/h • orbits 22,000 miles (36,000 km) above the Earth, • about a tenth of the distance to the Moon • able to capture images of the whole Earth disc • used by TV and weather satellites • this is why a satellite TV dish is bolted in a fixed position.

20. Geostationary Satellite

21. Geostationary Satellite

22. LEO Satellites • much closer to Earth than a geostationary orbit, • orbit at 400-800km (aircraft fly at 11km, ISS ~300km), • orbit at ~27,000 km/h (17,000 mph) • each orbit takes ~ 90mins, • has a smaller footprint than a geostationary satellite • can resolve finer detail (optical resolution ~40cm in 2010) • usually employ a group of satellites, • each in the same orbit, • at least one satellite is visible at any time, • possible to access satellites from any point on Earth, • GPS & satellite navigation (‘Navstar’) • use satellite ‘phone in remote locations (‘Iridium’ satellites), • global Internet access.

23. LEO Satellites

24. Advantages of Satellite Communication • can reach remote places • so people can be contacted wherever they are • e.g. areas where there is no cellular/fixed line connection • high bandwidth • many simultaneous calls can take place • video & audio can be transmitted in real time • cost of communication is distance independent • whether message is sent 10 km or 6000 km

25. Disadvantages of using Satellites • are expensive to set up and maintain • needs line of sight • can lose signal out of footprint or in built up areas • affected by weather conditions/interference • leading to signal degradation • distance from Earth • means messages takes time • can cause unacceptable delay on communications • general congestion in space • limitation on number of satellites in geostationary orbit

26. Uses for Satellite • Weather satellites • Communications satellites • Scientific satellites • Navigational satellites • Earth observation satellites • Military satellites

27. Weather Satellite

28. Weather Satellite • can see what's happening at the moment.

29. Weather Satellite • can see what's happening at the moment. • help meteorologists predict the weather

30. Weather Satellite • can see what's happening at the moment. • help meteorologists predict the weather • typical weather satellites include the Meteosat, GOES and NOAA satellites.

31. Weather Satellite • can see what's happening at the moment. • help meteorologists predict the weather • typical weather satellites include the Meteosat, GOES and NOAA satellites. • satellites generally contain cameras that can return photos of Earth's weather,

32. Weather Satellite • can see what's happening at the moment. • help meteorologists predict the weather • typical weather satellites include the Meteosat, GOES and NOAA satellites. • satellites generally contain cameras that can return photos of Earth's weather, • use visible and infra red imaging

33. Weather Satellite • can see what's happening at the moment. • help meteorologists predict the weather • typical weather satellites include the Meteosat, GOES and NOAA satellites. • satellites generally contain cameras that can return photos of Earth's weather, • use visible and infra red imaging • use either geostationary positions or polar orbits.

34. Weather Satellites

35. Weather Satellite

36. Weather Satellite

37. Weather Satellite Hurricane Katrina (August 2005)

38. Weather Satellite Hurricane Katrina (August 2005)

39. Scientific & EO Satellites

40. Scientific & EO Satellites • climatic phenomena

41. Scientific & EO Satellites • climatic phenomena • monitor, analyse and forecast future changes

42. Scientific & EO Satellites • climatic phenomena • monitor, analyse and forecast future changes • chart sea-surface temperatures

43. Scientific & EO Satellites • climatic phenomena • monitor, analyse and forecast future changes • chart sea-surface temperatures • global ocean colour • phytoplankton are a major influence on the amount of carbon in the atmosphere

44. Scientific & EO Satellites • climatic phenomena • monitor, analyse and forecast future changes • chart sea-surface temperatures • global ocean colour • phytoplankton are a major influence on the amount of carbon in the atmosphere • NASA monitors lake and reservoir height variations for approximately 100 lakes

45. Scientific & EO Satellites • climatic phenomena • monitor, analyse and forecast future changes • chart sea-surface temperatures • global ocean colour • phytoplankton are a major influence on the amount of carbon in the atmosphere • NASA monitors lake and reservoir height variations for approximately 100 lakes • track natural events in progress, • fires, floods, volcanic eruptions

46. Scientific & EO Satellites • climatic phenomena • monitor, analyse and forecast future changes • chart sea-surface temperatures • global ocean colour • phytoplankton are a major influence on the amount of carbon in the atmosphere • NASA monitors lake and reservoir height variations for approximately 100 lakes • track natural events in progress, • fires, floods, volcanic eruptions • deforestation

47. Scientific & EO Satellites • climatic phenomena • monitor, analyse and forecast future changes • chart sea-surface temperatures • global ocean colour • phytoplankton are a major influence on the amount of carbon in the atmosphere • NASA monitors lake and reservoir height variations for approximately 100 lakes • track natural events in progress, • fires, floods, volcanic eruptions • deforestation • astrophysical observations - Hubble Space Telescope

48. Scientific & EO Satellites 1975 1985 1992 Deforestation in Brazil

49. Scientific & EO Satellites 1975 1992 2006 Deforestation in Brazil http://earthobservatory.nasa.gov/IOTD/view.php?id=35891

50. Scientific & EO Satellites Mineral Exploration Image displays the mineral abundance layer. Red = Mica, Cyan/Green= Kaolinite, Blue= Alunite, Beige = Carbonate, Brown = Silica, Mauve = Iron