Image 1) Iceye satellite (https://www.businessfinland.fi/en/whats-new/events/2021/space-technologies-and-environmental-sustainability)
The Finnish designed Iceye system is 16 miniature SAR (Synthetic Aperture Radar) satellites that can make the topography imaging that covers the entire world in one day.
Those kinds of systems are the next-generation tools for making real-time imaging from a volcanic eruption and burning forests. The thing that makes radar satellites able to see things like burning fire is a radio spectrometer. The radio spectrometer sees the gases that are released from the burning material.
And another thing that the SAR- technology makes possible is to observe the rising gases. The radar sees the rising gas above the fire point. And then, the system can detect the suspected fires. But SAR-radar-based radio spectrometers also see poisonous chemicals. The idea in radio spectroscopy is that certain atoms are stressed by using radio waves. Those atoms are sending the electromagnetic echo. This echo is visible in the monitors.
In some visions, the entire earth will cover with the cloud of radar satellites. That cloud could give radar images in seconds from any point of the Earth.
Doppler radar is two radio antennas. Those receivers observe the transfer of the target. Those antennas are visible on the roof of the vehicle in image 4. The Doppler radar means that the system measures the changes of the wavelength of the incoming object.
Image 2) SAR types: Source: Wikipedia/Synthetic-aperture radar
Image 2B) Principle of the SAR radar. (Wikipedia, Synthetic-Aperture radar)
The Dober effect means when the object comes closer. The wavelength will turn shorter. When the object goes away. The wavelength turns longer. This thing is also used in astronomy. When the galaxy is going away from the Milky Way, its spectrum turns red. In this case, some galaxy comes closer to Milky Way its spectrum turns blue. The wavelength of electromagnetic radiation that it sends turns shorter.
Image 3) Doppler Effect: Change of wavelength and frequency caused by the motion of the source. (Wikipedia/Doppler Radar)
The SAR radar means the rotating radar antenna. Or actually, it means moving radar antenna. So the term "double SAR" means antenna that rotates and also benefits the satellite's movement. In some SAR systems, the antennas are on a long track. And they are moving back and forth. The "regular SAR" uses separate satellite movement at its trajectory. Or the rotation of the radar antenna.
Image 4) The US Weather Bureau's first experimental Doppler weather radar unit. Obtained from the US Navy in the 1950s (Wikipedia/Doppler radar)
The "double SAR" systems can mount to moving vehicles. Like aircraft, trucks, or trains. And that system can have the rotating doppler radar. The moving platforms are giving those radars "double SAR ability".
The distance of those antennas determines how accurate those radars can be. And new nanotechnology-based systems can have doppler radars that are connected to kilometers-long kevlar cable. In that antenna can be thousands or even millions of small doppler-antennas. And that system can give a very accurate image. The satellite itself might use nanotechnology and integrated microchips. So it might be a very small size.
https://www.hs.fi/talous/art-2000008582286.html
https://www.iceye.com/systems
https://en.wikipedia.org/wiki/Doppler_radar
https://en.wikipedia.org/wiki/Synthetic-aperture_radar
https://thoughtandmachines.blogspot.com/
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