Satellites, those not quite stars moving around up in the night sky, zooming along their own path and often bright enough to see with the naked eye. They are becoming more and more common in our atmosphere and even further up towards space. So let’s learn a little bit more about them as there are now thousands of them up there above us.
In the infinite expanse above Earth, a constellation of human-made satellites orbits, playing a pivotal role in our daily existence. From enhancing global communication to monitoring climate change, satellites are indispensable to modern life. This comprehensive guide delves into the fascinating world of satellites, exploring their orbits, the science behind their operations, and their diverse sizes and capabilities.
The motion of satellites is governed by the principles of orbital dynamics, a discipline that examines the forces acting upon objects in space. A satellite's orbit, the path it follows around Earth, is shaped by the gravitational pull of the Earth balanced against the centrifugal force from its motion. This equilibrium ensures satellites remain in a consistent orbit, neither drifting into space nor plummeting back to Earth.
If you would like a teaching resource on satellites, then you might consider my google suite science article on this topic or perhaps the offline version. Please do consider using them as they tie-in well with this blog post.
Satellites are categorized based on their orbits, with each type serving distinct functions:
Low Earth Orbit (LEO): Ranging from 160 to 2,000 kilometers (100 to 1,200 miles) above Earth, LEO is crowded with satellites used for Earth observation, the International Space Station (ISS), and some communication satellites. These satellites offer high-resolution imagery but require a constellation for continuous coverage.
Medium Earth Orbit (MEO): Positioned between 2,000 and 35,786 kilometers (1,243 to 22,236 miles), MEO is the domain of navigation satellites like the GPS system, offering broader coverage than LEO.
Geostationary Orbit (GEO): At approximately 35,786 kilometers (22,236 miles) above the equator, satellites in GEO maintain a fixed position relative to Earth, ideal for telecommunications, broadcasting, and weather observation.
Geosynchronous Orbit (GSO): Similar to GEO, GSO satellites orbit Earth once every 24 hours but can have inclined orbits, causing them to appear to move north and south over a single point on the equator.
High Earth Orbit (HEO): Beyond GEO, HEO satellites travel on highly elliptical orbits, providing extended coverage over high-latitude areas, crucial for communication and surveillance in polar regions.
Satellites vary widely in size and mass, tailored to their specific missions:
CubeSats and SmallSats: These range from as small as a loaf of bread to the size of a small fridge, weighing from a few kilograms to several hundred kilograms. Ideal for scientific research and technology demonstrations, their small size and mass reduce launch costs.
Medium to Large Satellites: Typically weighing from several hundred to several thousand kilograms, these satellites undertake a variety of tasks, including Earth observation, communications, and navigation. They are equipped with more sophisticated technology and instruments, offering greater capabilities.
Very Large Satellites: These behemoths can weigh up to several tonnes. Primarily used for high-capacity communications, they are positioned in GEO to provide extensive coverage for television broadcasting, internet services, and weather forecasting.
A visual is shown below which was taken from this link - thanks to the NOAA for making it. It helps visualize some of the satellite sizes currently in orbit.
Maintaining a satellite's precise orbit is critical. Satellite positioning involves continuous adjustments, facilitated by retro thrusters, to counteract gravitational influences from the Moon and Sun and the uneven gravitational field of Earth. These thrusters enable satellites to correct their orbits, maintain altitude, and, when necessary, deorbit at the end of their operational lives.
The operation of satellites encompasses a wide range of scientific disciplines, from physics and engineering to mathematics and computer science. The design, launch, orbital adjustments, and the data collected by satellites underscore the remarkable human achievement in technology and our quest for knowledge.
We can and do even track satellites across the entire planet with some independent organizations doing just that. For example, below is a screenshot from the website - https://satellitemap.space/ - It shows a staggering real-time number of satellites around the planet. There are also other sites too which show real-time data of satellites and space junk at any given time around the planet. I find them both fascinating and a little mind-bending to be honest.
The realm of satellites represents a significant chapter in the story of human technological advancement. From the variety of orbits that satellites inhabit to the incredible range of their sizes and capabilities, these marvels of engineering have become fundamental to the way we live, work, and understand our world. Hopefully, we won't need to keep an eye to the sky as satellites continue to work above us, but let's also hope that the sky doesn't become too cluttered with older satellites, space junk and random debris. In time, better monitoring, capturing and cleaning up of satellites and space junk will help future space exploration and travel. For now though, satellites are a modern marvel and we should be very grateful for their continued existence.
Thanks for reading
Cheers and stay curious
Oliver - The Teaching Astrophysicist