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Interview with a Space Scientist: Prof. Martin Barstow
Interview with a Space Scientist: Hazel McAndrews
Working at the European Space Agency
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Types of Satellites

Communications Satellites

There are many possible job for a satellite. The earliest and still one of the most important was telecommunications. Telstar 1 was launched in 1962 and carried the first live television broadcast between the United States and the UK. It could also carry a hundred simultaneous telephone calls. Before this calls had to be carried by cables laid across the floor of the Atlantic Ocean; capacity was very limited and only governments and the world’s wealthiest people could afford to use them. Nowadays a single satellite can carry hundreds of thousands of telephone calls at the same time as numerous television channels and links between computers for applications such as the internet.

Space Science Satellites

Credit: NASA, ESA,
J. Hester and A. Loll (Arizona State University)
A great deal of what we now hear about satellites is to do with space research and astronomy. The best known space telescope is Hubble. As it was launched in early 1990 it has long outlived its expected life but continues to return excellent images. The advantage of placing a telescope in space is that its vision is not affected by the Earth’s atmosphere. Other orbiting telescopes look at different wavelengths and so we can look into space with eyes that cover radio waves, infra red, visible light, ultraviolet, X-rays and gamma rays, in fact the whole electromagnetic spectrum. In addition manned space science satellites, such as the International Space Station, allow us to study a wide range of subjects from how to grow almost perfect crystals (for engineering and computer applications) to the long term effects of weightlessness on the human body (vital if we ever hope to travel to Mars).

Navigation Satellites

Whenever we take a flight we tend to forget that the position and altitude of the aircraft is constantly being checked using the GPS (Global Positioning Satellite) system. This constellation of satellites orbit the Earth and allow us measure our position to an accuracy of a few metres. The GPS system was created by the American armed forces for their own uses but is now used more often by civilian users for navigation and surveying. A new system, Galileo, currently being designed by the European Union will be a solely civilian system that will allow us to measure positions down to a few cm along with times and speed with incredible accuracy. One application for our emergency response team would be to have GPS receivers near danger hot spots. Before a volcano explodes, the magma chamber underneath it fills. This makes the ground above it rise up giving us an early warning of an eruption.

Earth Observation Satellites

These satellites are probably the most important for our mission. A huge fleet of craft in orbit above the Earth are constantly monitoring land and sea temperatures and weather patterns, together with information on crop health, pollution, mineral deposits and many other factors. In fact our knowledge of the world we live in today would be impossible without Earth orbiting satellites.

Review Questions

  1. Put the following objects in the right group (natural satellite, artificial satellite & not a satellite). Try to identify which planet the satellites orbit. (You might need to search the internet to find out what some of them are before you decide where to put them).
    The International Space Station, Phobos, Triton, The Hubble Space Telescope, Oberon, The GPS satellites, Titan, Mars Express, Cassini, The Moon, Voyager 1, Charon, Mars Rovers “Spirit” & Opportunity”, Europa, Gravity Probe-B, Landsat, Terra (EOS),

  2. Why were the earliest satellites controlled by military powers rather than civil? Think about how much it costs to get into orbit. The earliest rockets were designed to deliver nuclear bombs to their targets.

  3. Before communications satellites, only a handful of transatlantic phone calls could be made at the same time. How would that have affected the cost and so who could make these calls?
    As communications satellites offered more and more capacity what would have happened to the cost of calls? What effect would that have had on who made the calls?

  4. Before the space age almost all astronomy was done with visible light (radio astronomy only became possible after RADAR was developed during the second world war). Why was astronomy with all the other wavelengths of light (Infra-Red, Ultra-Violet, X-Rays and Gamma Rays) impossible before then?

  5. GPS technology is now being used in many new situations. Produce a list of where it (and the new European Galileo project) can be used. You won’t get a complete list but do your best to describe how they are used.

  6. Earth observation satellites are being used in more and more applications every year. Between now and your mission, keep an eye on the news to find out what satellites are being launched or returning important data. You could log on to the ESA (www.esa.int) and NASA (www.nasa.gov) web sites to find much of the information you need.


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