When did you last use a satellite?It is probably a lot closer than you think. Satellites do a lot of jobs, they help us talk to one another, they monitor our weather and let us know where we are. We use them to map our world and some help to rescue ship wrecked sailors or get aid to disaster areas.

OrbitsHow do satellites stay in orbit? Why don’t they fall down?They do fall, but they fall around the Earth. If you drop a stone over a cliff it falls about five metres in the first second. If you throw it horizontally at 7900 metres per second (that’s some throw) it still falls five metres in the first second, but

by that time the Earth has curved away by that same five metres. So it keeps going. Eventually (after about 92 minutes) it would get all the way around the Earth and hit you in the back of the neck (if you were stupid enough to still be standing there).

Where are they now?Satellites fly in different orbits, depending on what they do. The International Space Station orbits at about 340 km above the Earth, at an angle of 51.6º, so that the Space Shuttle and the Russian Soyuz launcher can reach it. You can find out where it is now at:

http://spaceflight.nasa.gov/realdata/tracking/

Envisat, the European Space Agency’s Earth Observation satellite, has an orbit 783 km going over the poles, so it gets to see everywhere on Earth twice a day. ESA has a site tracking all its satellites at:

http://www.esa.int/SPECIALS/Track_ESA_

missions/index.html

The Hubble Space Telescope orbits at 600 km, circling the Earth every 96 minutes. This allows it to be serviced by the Space Shuttle.

The GPS navigation satellites fly in a number of orbits at 20200 km, each at an angle of 55º to the equator. This means that there are always at least four satellites in the sky from any point on the ground.

Communications satellites fly at an altitude of 35845 km above the equator. They take precisely 24 hours to circle the Earth, so that they appear to hang in a fixed point in the sky.

You can sometimes see one of the nearer satellites just after sunset, because while you are in darkness the satellite can still be in sunlight. Use one of the tracking sites to find out when one is going to go over you.

• Do you have Sky TV at home? The SKY service is broadcast via satellites. The signal is then relayed to your home via the small “sky” dish (receiving antenna) on the side of your house.

• All television channels are also broadcast initially via satellites – without the satellites there would be no TV!

• Satellite based communications help us to keep in touch with one another wherever we are in the world or in space!

And somethings you might not realise initially came from technology developed for use in space…

• Lightweight blankets – these “foil” blankets often used by runners at the end of a race and by emergency services were originally developed for protecting satellites in space.

• Smoke Detectors – originally developed for use on the Skylab Space

Station, they are now found in virtually every home.

• Cordless Tools – now used everyday, items like cordless drills were developed for the Apollo astronauts and used during the Moon landings.

• Earth Observation satellites like Envisat and Meteosat provide us with accurate data used for weath-er forecasting.

• In the wake of the Tsunami in 2005 satellites provided vital information to emergency services detailing the areas most affected and helped get aid to those areas.

• Earth observing satellites are continually monitoring our planet and the recording the changes occurring due to global warming, this data is used to try and help cut emissions and try to prevent further damage to our planet.

If you thought GPS was just about SatNav you were mistaken! Look deeper and you’ll find GPS has many applications…

• GPS is used to timestamp all transactions made at our cash machines and in our banks

• GPS timing is used in telephone networks

• GPS is used by Taxi companies not only to help them find the quickest route to a des-tination but also to track them from the call centre such that when someone calls for a taxi the nearest one to the pick up can be sent.

Z W I B V S N E P L B K E O E L I L A G K A T A H V P M W P M E S L T C I Y K S W I A E L H G H J K R O T G I T E V A N S U N Q P O K R I A U D A B R A D I O D E N V I S A T W A B Y O I S I V E L E T

Find the words in the word search below describing space in your daily life.

SATNAV GALILEO WEATHER SKY DAB RADIO TELEVISIONGPS ENVISAT

Victoria Hodges

Astrium Ltd, Stevenage, UK, Graduate Development Programme.

Send in your questions to our space experts at:Voyage, BIS, 27/29 South Lambeth Rd, London, SW8 1SZEmail: voyage@bis-space.comWeb: www.bis-space.com/education

Although I always had an interest in space, it wasn’t until I was in my final year at secondary school (aged 15) that I really thought about a career in the space industry. This was mostly thanks to my physics teacher at the time who encouraged my enthusiasm for the subject. Not knowing much about engineering, I decided to follow the physics route into space.

I’m a graduate engineer, recruited into the Attitude and Orbit Control Systems, Guidance Navigation Control & Flight Dynamics Group Stevenage, UK, working on formation flying studies. I spent three months working in Toulouse, France in the Advanced Studies group (formation flying) and currently working on the Aeolus project doing Systems Engineering and Operations support. In my final year of university I decided to apply to EADS Astrium, and was taken onto their graduate programme, a two year scheme designed to allow new graduates to experience a wide range of roles within the industry.

All im

ages credited to NA

SA and ESA

Edited by Victoria Hodges (Astrium) and Bob Parkinson, Designed by Melanie David-FeveckPublished by the British Interplanetary Society. Registered Company No: 402498. Registered Charity No: 250556.

In every issue of Voyage some of your frequently asked questions relating to space and space technology will be asked by our space experts. Send in your questions for our experts and yours might appear here. Which was the first ever satellite in space?The first satellite to be launched was Sputnik 1. Launched on 4 October 1957, Sputnik 1 was built by the Russians. It was the creation of Sergi Korolov. Sputnik remained in orbit for 91 days before burning up in the earth’s atmosphere.

How many satellites are orbiting the Earth?It is estimated that there are approximately 8000 satellites in orbits around the Earth.

How much does a satellite cost?Different satellites cost different amounts. The large communications satellites that broadcast our TV signals cost around $100 million GPS satellites cost around £150 million whereas scientific satellites like the Hubble telescope can cost around $2000 million.

How do satellites get into space?Satellites are put into space by large rockets. These rockets usually have stages, the first stage is used at the beginning of launch to give the rocket the initial boost into space. The second stage is then ignited and finally the third stage is used to put the satellite into it’s desired orbit.

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