Not too long ago we learned what exactly a satellite is – and the fact that a satellite can be naturally occurring, not just man-made.
But for those satellites that are man-made, their definition can be broken down even further: namely, what types of man-made satellites are there, and what do they do?
Man-made or artificial satellites capture huge amounts of information from space and transmit it back to us for either scientific research or communication purposes, while others might provide information about tomorrow’s weather forecast. Today we delve a little deeper into some of those satellites and their functions.
To put it simply, these satellites are basically giant telescopes in space. Because they orbit Earth – and therefore aren’t inhibited by Earth’s atmosphere, light pollution or electromagnetic radiation – astronomical satellites can see up to ten times better in space than we can from telescopes here on Earth. These satellites observe other galaxies and distant planets, and transmit important data for scientific research regarding black holes, dangerous rays from the sun, asteroids as well as natural resources on other planets.
Biological satellites are designed to carry living things into space, such as organisms, plants and seeds, generally for scientific experimentation. Sputnik 2, the satellite that carried Laika into space, was actually a biosatellite (RIP Laika). Other biosatellites have carried mice, frog eggs, guinea pigs, garden spiders, fruit flies, jellyfish, newts, silkworms, bacteria and wheat seedlings, to name a few.
Communications satellites, or comsats, are vital for us in so many ways. They enable us to call, text or send a quick pic to anyone in the same country, or even in a different country for that matter. Before comsats, mountains could literally separate you and the friend you wanted to contact. Since the transmission signal on your phone would only go in a straight line, a mountain could potentially block that signal. Comsats enables signals to be sent from anywhere, to everywhere. So the next time you flip on the telly, use your phone, play the radio, use the internet or… well, let’s just say the next time you do anything that involves some form of communication, remember that you have satellites to thank.
ESA’s Earth Observation Programmes are given a nice intro in this short video. Credit: ESA.
Earth observation satellites
This type is pretty straightforward: Earth observation satellites observe Earth. But what they observe actually depends on a few factors, such as the type of orbit they’re in, their payload, and the imaging instruments they use. Generally speaking, Earth observation satellites monitor any environmental changes that could affect humans, such as bushfires, volcanoes and eruptions, hurricanes, ice shifts and our oceans. These satellites can even aid farmers in knowing which crops to grow for the upcoming season.
Ever used a map function on your phone to find directions to a certain location? Then you should probably thank navigational satellites, also when combined referred to as the Global Positioning System (GPS). By communicating through signals sent between them, navigation satellites can determine an exact location anywhere in the world.
Here in Australia, we use the U.S.’ satellite navigation system, which you would know as the Global Positioning System or GPS. Other countries/parts of the world have their own global navigation satellite systems – Japan uses the Quazi-Zenith Satellite System (QZSS), Russia uses the Russian Global Navigation Satellite System (GLONASS), China uses the BeiDou Navigation Satellite System, the European Union uses the Galileo system, and India uses the Indian Regional Navigation Satellite System (IRNSS).
(Un)officially referred to as spy satellites, recon satellites are any Earth observation or communications satellites deployed for military, surveillance or intelligence purposes. There are several major types of recon satellites, including: electronic-reconnaissance, missile early warning, nuclear explosion detection, radar imaging and photo surveillance. (The details on such missions, we’re going to assume, are classified.)
Tethered satellites are satellites that use space tethers, normally for research purposes, and are comprised of three parts: the base-satellite, the space tether, and the sub-satellite. When launched, the base-satellite usually contains the tether and sub-satellite until they reach space and can be deployed. The tether connects the sub-satellite to the base-satellite; the base-satellite can be anything from another artificial satellite to a space station, spacecraft, or even a natural satellite like the Moon.
Tethered sub-satellites can be deployed from the base-satellite through a thin wire like a crane and hence reach further without leaving orbit. Research on things like electrodynamic propulsion, artificial gravity, and electric sails could all use tethered satellites for experimentation.
Want to see one in action? Check out this epic NASA video from the 90s on How Tethered Technology is Used in Scientific Research.
Want to know who – or what – to thank for keeping Melbourne up-to-date on its four seasons in a day? Say g’day to the weather satellite. These sats monitor and send back data regarding Earth’s weather, climate and information regarding future forecasts. Similar in function to Earth observation satellites (in fact, the two often overlap in use and function), weather satellites are more specifically used for meteorological reasons and even some environmental disasters such as oil spills and ozone holes.
In fact, the first television image of Earth from space was taken by a NASA weather satellite. The Television Infra-Red Observation Satellite (TIROS-1) snapped the shot on April 1, 1960, and is celebrated as the world’s first successful weather satellite.
Killers and kidnappers: satellites that sound like they belong in a sci-fi movie
Apart from these mostly commonly known satellites, there are others that are not equally familiar to us – or that we do not know much about at all. One type that especially caught our eye was the so-called ‘killer satellite’.
Until now, there has not been any satellites known in space that have been thought to have been used for actual missile attacks. However, between 2013 and 2015, Russia launched a series of three satellites, code named Kosmos-2491, Kosmos-2499 and Kosmos-2504, into space without an established cause. These satellites have been idle in space, floating around like space debris and have not caused much of a buzz – until last year.
Two of the satellites started showing signs of activity again as they moved around and changed their course of orbit, something that is not too common for space debris. The unexpected movements of these satellites have raised a lot of speculation whether they are inspector satellites, or even if they are in fact prototypes for anti-satellite weapons. But nothing is still known for sure on the subject.
Similar creations have previously been tested by a few countries where the aim is to disable satellites already in orbit, but these have all been launched from Earth and have therefore not been in orbit. CNN reported in 2016 on the Shiyan, a Chinese satellite which seemingly had the potential to ‘kidnap’ or grab other satellites using a prototype robotic arm; and the US recently deployed the Laser Weapons System (LaWS) in the Persian Gulf, the world’s first active laser weapon. The LaWS is focused on threats at sea, but this kind of laser technology is being looked at by multiple countries to test lasers that can reach space. (Fortunately, says Laura Grego of the Union of Concerned Scientists, these lasers would likely be more of a nuisance than anything else – ‘like someone shining a flashing in your eyes’, making it hard for the satellite’s sensor to ‘see’.)
Whether for earth observation, communications, navigation or anything in between, satellite technology is responsible for a lot of how our modern societies function. Many new satellites are still being launched for different scientific reasons, and let us tell you – the future is looking bright. Many new projects are pointing towards the development of satellites that will be able to repair spacecrafts already in orbit, some that will be able to spot minefields meaning some of the worst affected countries could be completely cleared by 2023, and some that will assist in creating even more autonomous vehicles. Strap yourselves in – the future is here!