We have all grown up aware that satellites are orbiting the earth put there since space travel became viable. For most of us, satellites don’t get a second thought, but have you ever wondered how they work and why we use them?
It is pretty clever to consider that satellites can be so far away and yet be sent signals from here on earth and take those signals and transmit them back to us making a sort of floating communication system in a neat little container. This is because they feature a transponder which is a device that enables the transmission and receipt of radio signals. They are also pretty tough creations as during launch the orbital velocity reaches speeds of up to 175000 miles an hour which is pretty rough on the construction. When they reach space, temperatures become extreme, and they can also find themselves exposed to radiation. Despite these issues, engineers have been able to create satellites that have a lifespan of around 20 years. A key design feature is weight as it also costs a lot more to launch something that is heavier. Finally, as if all these challenges weren’t enough for satellite designers and builders, there is no maintenance crew available, so they have to be completely reliable and unlikely to break down. This would render them useless and a piece of scrap floating in space.
When it comes to building a satellite, everything must focus on the communication system as this is the main component and purpose of building it in the 1st place. This will include the transponder and antennas that are used to retransmit and receive signals coma it also requires power, which comes in the form of solar panels and the propulsion system. A satellite will also have rockets as it needs to be propelled into space. It also has to have a location system to push itself to the correct location and correct any course defect. It may surprise you to learn that over a period of 12 months a satellite sat in geostationary orbit can’t actually move from either North to South or from East to West due to the gravitational pull created by the sun and the moon. The amount of movement is only a degree, but it does matter so; therefore, the satellite has to have the thrusters that are needed to correct any change in position. Technically this is known as station-keeping by using these built-in facilities known as attitude control. This is all done by the satellite programming automatically. Again, all of this must be carefully calculated because the satellite is rendered useless if it runs out of fuel at which point it can no longer be controlled from the earth and becomes floating debris drifting into space inoperable condition.
The Life Span
So, determining the life span of a satellite is down to careful calculations. While it is in orbit, it will be operating at all times and therefore needs the power to do so. The solar panels provide the greatest natural power source possible. Still, there does have to be backup batteries on board as there are times when the sun is not accessible to the satellite due to its position, and the earth is blocking the trajectory. The batteries are rechargeable, so once the satellite moves back into the sun’s path, it will recharge any battery power used. All of these components have to be able to function well in massive temperature extremes; it can get as cold as minus 150 degrees and as hot as positive 150 degrees. There is also a danger of radiation; therefore, it must be shielded and generally aluminium and other materials that are resistant to radiation are used by this innovative design. The temperature control system known as a thermal system is able to ensure that the electrical components can continue to work correctly despite the massive highs and lows of the temperature. So if it thinks it’s too hot, it will activate a cooling mechanism, and when it gets cold, it can also heat itself.
Tracking satellites is done by a system called TT&C which stands for tracking telemetry and control. This links the control station on earth to the satellite with two-way communication. So, if need be ground-control can take over thermal systems or propulsion systems and can also track progress. A satellite’s weight very much depends on its purpose; some weigh as little as one kilogramme. In contrast, others can actually weigh more than 6500 kilogrammes. It basically depends on what job they are sent into space to be able to do whether we are providing television or other vital processes.
Location of Satellites
We send satellites into space at three different orbit levels: low earth orbit, medium earth orbit, and geostationary or geosynchronous orbit. Again, this depends on what they are going to be doing and can sit at altitudes of between 160 kilometres and 1600 kilometres above the earth below for the low earth orbit satellites. At the other end of the scale, geostationary orbit satellites can go as high as 35,786 kilometres above, which gives them the ability to orbit in 24 hours, so they move at the same speed as we stay fixed in one spot. If you want global coverage, this can be achieved by three geostationary orbit satellites, ten medium earth orbit satellites or 20 low earth orbit satellites.