Think of satellites as eyes in the sky, providing sweeping views of volcanoes, wildfires, landslides and hurricanes. They’re used for navigation, communications, weather forecasting and even spying.
Data from satellites can be used to help scientists track changes in forests, predict weather patterns and measure ozone in the atmosphere.
Amnesty International uses remote sensing images from satellites, aircraft, drones and even balloons to monitor conflicts and expose abuses of human rights in areas that would otherwise be inaccessible on the ground for safety or security reasons.
Unfortunately, terrorists also use such images to plan attacks.
Earth observation applications are almost without limits and satellite data is a powerful tool. When you’re lost, it can guide you home using GPS. There are thousands of satellites in space and, like mobile phones, they’re getting smaller and smarter. Perth-based company Sky and Space Global has already developed nano-satellites the size of a shoebox.
Before 1957 the word satellite was mainly used in astronomy applications for natural moons or planets orbiting. In 1957 the former Soviet Union launched a small metal ball called Sputnik into outer space – the first artificial satellite. The space age was born .
Artificial, or man-made satellites orbit Earth, launched into space on rockets, and just as different seats in a theatre provide a different view of the stage, so do different orbits when it comes to looking at Earth.
There are three types of Earth orbit: high, medium and low. NASA says that weather and communications satellites tend to have a high Earth orbit, farthest away from the surface. Navigation and specialty satellites, designed to monitor a particular region, have a medium Earth orbit, while most scientific satellites, like the International Space Station (ISS) have a low Earth orbit.
Collisions are rare because care is taken to place a satellite into an orbit to avoid others but two communications satellites — one US and one Russian — did accidentally crash into each other in space in 2009.
NASA, the European Space Agency, the National Oceanic and Atmospheric Administration and the United States Geological Survey were early developers of satellite imaging. US-based DigitalGlobe and European-based Airbus are the biggest commercial providers.
Countries with the most satellites in space include the US, Russia, China and Japan, but India is quickly catching up. Just last month, it launched a record-breaking 104 satellites on a singe rocket, including 101 “nanosats” measuring 30cm by 10cm belonging to a US-based Earth-observing company called Planet. European countries France, Germany and Italy have also launched many satellites.
All this makes for a lot of space junk over time. NASA says there are currently more than 500,000 pieces of debris the size of a marble, or bigger, orbiting Earth. More than 20,000 pieces are the size of a softball and there are many millions of pieces so small that they can’t be tracked, all travelling at speeds up to 28,160kmh, which means that even a tiny paint fleck can damage a space shuttle window.
Did you know?
NASA launched its first satellite, Explorer 1, in 1958.
Skylab, the first US space station, put Esperance on the world map when it crashed on WA’s south-east coast on July 12, 1979. It was launched into orbit by NASA in 1973 and manned by astronauts to do science experiments, including X-ray studies of the sun, before being abandoned in space in 1974.
Skylab did 34,981 orbits of Earth before it came crashing down in a spectacular fireball over Esperance and Balladonia on the Nullarbor Plain, scattering space junk for hundreds of kilometres along the way.
Dr Halina Kobryn, of Murdoch University, specialises in satellite data analysis for environmental applications. She is co-supervising PhD student Stuart Dawson’s thesis on bilbies that’s using data from Landsat and TripleSat to monitor this vulnerable species in WA’s far north.
Bilbies, like all animals, have particular habitats that they prefer to live in. As bilbies are nocturnal, it makes tracking them even more tricky. When a mining company, or a farmer, wants to see what animals are on their land, it’s very hard to go out at night to find them, so looking at satellite imagery can tell us if the area is good bilby habitat. Our research is trying to match up exactly where they live on the ground to the imagery that can be taken from a satellite.
What do the satellite images show?
Because a satellite image is looking down, it shows whatever is tallest. If on a desert sand dune, it just shows the sand. However in a rainforest, it shows the top of the canopy because, like a normal camera, it cannot see through the leaves. We can then use the various characteristics of the image to measure how dense the vegetation is and how green the plants are. We can even tell the difference between bare ground after a bushfire and a gravel road.
How long has this technology been used in this way?
This satellite technology has been around for some 30 years but only in the past 20 years have we seen wider applications in wildlife conservation. Some satellites have very long archives. Landsat satellites go back to the mid-80s and are free, well-calibrated and they cover most of the planet. They allow scientists and land managers to track changes of an area over time and relate it to other measurements we have, such as rainfall, heat waves, flood and fires or land clearing.
Have bilby habitats changed over time?
Yes, the vegetation in our study area changes every year because large fires occur often in northern and arid Australia. While these can be devastating for animals, the different stages of regrowth attract different species in the search for food. For example, certain animals like to eat the young new shoots that come through after a fire. Some prefer vegetation that is bit more mature, while others like it nice and thick before it burns again. Using satellite imagery from multiple years, we can look at the recovery of areas after fire and predict what animals will be there at different times.
If it wasn’t for the satellite images, would we be still be able to keep track of bilbies? Or would it mean laborious field work?
We are still at the stage where we have to look for bilbies by doing laborious field work, so we can compare those records to our satellite images. In the future, when we have developed our understanding, we may be able to predict where bilbies will be based on satellite imagery alone.
Is it legal?
Privacy will become a major issue as satellite imagery continues to improve, enabling identification of individuals. It’s a legal minefield because satellites do not distinguish between public and private property, so can monitor anyone.
The 1967 Outer Space Treaty declares that outer space cannot be claimed as national territory, which means satellites can travel over any part of Earth, though they do need to be registered and countries do need to take responsibility for their space junk.
What is GPS?
GPS makes it easy to pinpoint location and get to where you’re going without getting lost. It stands for Global Positioning System, a satellite-based navigation initiative that uses radio signals to work.
It was launched by the US military in 1973 but a version was made available for civilian applications in the 1980s. It’s owned and operated by the US Government and is free for anyone with a GPS receiver, such as a smartphone, tablet or car-navigation device.
Other countries have similar satellite-based navigation systems, such as Russia’s Global Navigation Satellite System (GLONASS), the European Union’s Galileo and China’s BeiDou Navigation Satellite System.
To calculate your position (latitude, longitude and altitude) and pinpoint time, the GPS receiver needs to lock on to four satellites simultaneously. It works by measuring how long it takes a signal to travel between a satellite and your device.
You don’t need an internet connection but some apps such as Google maps need one to work, unless you have downloaded and saved the data to your device.
GPS is accurate to 7.8m, 95 per cent of the time, anywhere on Earth.
The number of satellites in the GPS system can vary from 24 to more than 30. Daily updates are available on the US Federal Aviation Administration website. Currently there are 32, all in a medium-Earth orbit, which is about 20,000km above us. They carry atomic clocks, which provide extremely accurate time, and are powered by solar energy with rocket boosters and battery backup in case there’s an eclipse.
International Space Station
The International Space Station (ISS) is a satellite the size of a football field in low-Earth orbit and the third brightest object in the night sky.
It’s easy to spot and looks like a fast-moving plane, only much higher and travelling thousands of kilometres an hour faster.
The ISS was launched in 1998 and is a shining example of international cooperation for scientific research by five participating agencies — the National Aeronautics and Space Administration (NASA), Russia’s Roscosmos, the Japanese Aerospace Exploration Agency (JAXA), the European Space Agency (ESA) and the Canadian Space Agency (CSA).
There are currently six crew on board and it’s been visited by astronauts and cosmonauts from 17 different nations over the past 18 years. Seven space tourists have also made the trip, each paying between $26 and $52 million.
Russian Soyuz rockets transport crew to and from the ISS. The journey takes six hours, less time than it takes to fly from Perth to Mauritius.
You can see the ISS for two minutes over Perth at 7.55pm tonight if you look 10 degrees above SSW and for three minutes at 7.04am tomorrow (10 degrees S). For other sighting times during the week go to spotthestation.nasa.gov/sightings and type in your location.
You can go anywhere, anytime on Google Earth, which uses satellite images to bring the world to your laptop.
Visit London,Tokyo and Moscow in 3D, explore national parks and walk down Wall Street in New York. Plan a trip, or simply explore.
A lot of Google Earth’s remote sensing data comes from the US-based Landsat program, which is managed by NASA and the US Geological Survey. It was launched in 1972 with Landsat 1 to gather facts about the natural resources of the Earth and has been used by scientists and researchers to monitor vegetation growth, deforestation, agricultural land use, erosion, snow fall and melt, as well as urbanization.
Landsat 8 images the entire Earth every 16 days in conjunction with Landsat 7 and data is available to download, free, from GloVis, EarthExplorer or the LandsatLook Viewer within 24 hours.