Our reliance on space tech is greater than many imagine. We use satellites to capture pictures of our planet, monitor climate change, prevent illegal activities on land and sea, create detailed maps later used for navigation, and much more. And even though modern spacecraft can be equipped with many different sensors, satellite camera technology remains the primary means of obtaining detailed information about our planet from space. But how exactly does it all work? Below, we explain the basics of satellite camera use, and its operation logic, and offer some practical examples of satellite applications.
How does a satellite camera work?
In essence, a satellite camera works the same as a traditional one — it focuses light on a digital sensor to capture an image. However, in the space environment, a more complex satellite camera system is required to shield the technology from radiation, extreme temperatures, and other hostile factors that interfere with its proper operation. Besides an optical sensor, also found in terrestrial cameras, satellites are equipped with imaging sensors suitable for different light wavelengths, i.e., visible, which we use on Earth, infrared, or ultraviolet.
Next, space images should be transmitted back to Earth for analysis, which is why satellites have radio transmitters to receive and send data. Ground stations receive raw images from space and process them into ‘habitual’ pictures. Normally, processing implies removing noise and distortions caused by our planet’s atmosphere.
One more vital piece of equipment to minimize the level of distortion is stabilization and control systems. They literally help stabilize satellite cameras to reduce unnecessary motion and capture clear images. Normally, a satellite camera stabilization system includes reaction wheels, thrusters, and gyroscopes.
The final ‘component’ that ensures satellite camera operation is its placement. Depending on mission goals, satellite cameras are deployed into various orbits to ensure each spacecraft covers its designated area of interest (AOI). But what mission goals could those be?
What are satellite cameras used for?
Even though satellite cameras can accomplish a wide range of tasks, the most common applications include:
● Earth observation: these satellites monitor ocean covers, and vegetation areas, detect illegal mining, etc.
● Weather forecasting: this tech analyzes atmospheric conditions from space and sends data back for analysis, resulting in our habitual weather forecasts.
● Military and defence: military satellites are used for reconnaissance and collecting intelligence on troop movements, missile launches, etc.
● Navigation: besides GPS, there are other navigational satellite constellations, such as Russian Glonass or EU’s Galileo.
● Astronomy: of course, deep space cameras are used in scientific research, where Hubble Telescope, mounted on a satellite, is the most famous example.
The main types of satellite cameras explained
There are many types of space imagers, classified by imaging systems and specific applications described above. Still, the primary classification parameter that matters most is satellite camera resolution. Today, most spacecraft can that capture images in high, medium, or low resolution. Besides, multispectral and thermal imagers also grow increasingly common.
High-resolution cameras, for example, can capture incredibly detailed images of our planet and can discern objects no more than a few centimetres in diameter. Such satellite cameras are usually used for detailed mapping, urban planning, or military surveillance.
Medium-resolution cameras cannot capture such a level of detail, but they can cover larger surface areas, ranging up to a dozen square meters. This kind of camera, which includes Sentinel-2 satellite, is especially common in climate and environmental monitoring because they ensure that ‘middle-ground’ between detalisation and larger coverage.
Expectedly, low-resolution cameras capture an even lower level of detail, but they can cover larger AOI. Typically, one such imagers monitor up to one square km of surface, which is more than enough to forecast weather, keep track of global climate patterns, or monitor ocean currents.
Multispectral and hyperspectral cameras are a slightly different matter because they can capture images in different bandwidths, not just in visible light. Multispectral cameras can capture up to ten different bands, whereas hyperspectral ‘see’ up to a hundred. This is an advanced tech example used in mineral exploration, commercial agriculture, and military surveillance, too. These imagers can even provide information on our planet’s composition, and, what’s more important, they do not depend on light to capture images.
Finally, thermal cameras detect heat. They are also called infrared because that’s what they essentially capture — infrared radiation emitted from hot objects on our planet’s surface. Those could be wildfires or volcano eruptions, and such cameras are used for disaster monitoring. But analyzing heat waves also has military applications, i.e., searching for hidden objects, and is also quite valuable for studying heat islands in urban areas.
These are only some of the top examples of how satellite cameras help us advance our science, keep track of vital processes on our planet, and much more. However, this list merely scratches the surface, and the range of practical applications continues to expand. Right now, it’s safe to assume that satellite tech will keep shaping our daily routine and space exploration further, so we will have to wait and see how this technology evolves.
