How Do Satellites Work?
#19 How do they die?
Ah! It’s been a while since I wrote a Technology article. As a kid, I learned that the moon is a natural satellite 🌕. Then I learned about artificial satellites🛰, however, never understood completely their purpose until much later. Whenever I questioned my teacher all I got was “Do you watch TV? That’s because of the satellites”. Well, it’s true but I wanted to understand the “How” part.
What’s a satellite?
In layman’s terms, it’s an object that revolves around a planet. If it’s a natural object then it’s a natural satellite else a man-made one. Our moon and other planets’ moons are examples of natural satellites. The major purpose of artificial satellites is to transmit information to and fro from the earth. Thanks to them, we are able to enjoy the ongoing world cup and TV. Apart from entertainment, they facilitate studying the environment, climate change, surveillance and much more. Thanks to them we can have the internet even in sparsely populated and unexplored regions.
Did you know that satellites technically are actually falling onto the earth? 😯 Yes, you heard that right! Just like a ball returns back to Earth, the satellite would eventually return back to Earth if not for the orbital velocity, height from the earth’s surface and the occasional corrections from the deviations due to environmental factors.
How do they work?
A satellite is a sophisticated communication device which receives signals from the earth and retransmits them back to Earth using something called a transponder —an integrated receiver and transmitter of radio signals. They are launched into space by using rockets as a payload — in simple terms, space cargo. Since the cost of rocket launches is expensive, satellites need to be extremely small, lightweight and durable in comparison to rockets carrying them.
Once launched into space, they need to function on their own, as nobody is going to be present if things go wrong. They must operate at extreme reliability of more than 99.9 per cent in the vacuum of space with no prospect of maintenance or repair. A satellite has to absorb the shock of being accelerated during launch up to the orbital velocity of 28,100 km (17,500 miles) an hour and a hostile space environment where it is exposed to cosmic radiation and extreme temperatures from −150 °C (−238 °F) to 150 °C (300 °F) for its projected operational life, which can last up to 20 years on an average.
The major modules of a satellite consist of a communication module — antennas and transponders, the power module — solar panels that provide power, and the propulsion system, which includes the rockets that propel the satellite. A satellite needs its own propulsion system to get itself to the right orbital location and to make occasional corrections. A geostationary satellite can deviate up to a degree every year because of the gravitational pull of the Moon and Sun. A satellite has thrusters that are fired occasionally to make adjustments in its position.
Satellites operate in three different orbits:
Low Earth orbit (LEO) - 160 km and 1,600 km (100 and 1,000 miles) above Earth
Medium Earth orbit (MEO) - 10,000 to 20,000 km (6,300 to 12,500 miles) from Earth
Geostationary or geosynchronous orbit (GEO) - 35,786 km (22,236 miles) above Earth
The area between LEO and MEO is an inhospitable environment for electronic components due to energy-charged particles from the solar winds aka the Van Allen radiation belt. So no satellites are deployed in this region. GEO satellites complete one orbit in 24 hours and thus, as the name suggests, remain fixed over one spot.
Where do satellites go to die?
Nothing lasts forever! Similar to any other machine like a laptop or a mobile, satellites grow old and eventually die due to regular wear and tear and environmental factors. A satellite’s life span is determined by the amount of fuel left to power the thrusters one last time. Once the fuel runs out, the satellite eventually drifts into space and out of operation, becoming space debris. For the closer and smaller satellites, engineers will use their last bit of fuel to slow them down so they will fall out of orbit and burn up in the atmosphere. Further satellites are instead sent even farther away from Earth and they remain there for eternity until humans become advanced enough to clean up their trash using space garbage shuttles.
What about bigger things like the ISS (International Space Station) and larger spacecraft in low orbit? They might not be able to burn up completely before they reach the earth’s surface. There is a place on earth which is farthest from any human civilisation. This place has a nickname—the Spacecraft Cemetery! It’s in the Pacific Ocean and these satellites come here for their final journey. Hope you learned something new today as I did.
📚 Here are some useful study materials for deeper understanding:
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~ Nithin