Apparently, Russia has been disrupting ESA (European Space Agency) Sentinal-1 radar satellites when they operate over areas of Russia, like Eastern Ukraine, where there is a lot of Russian military activity. It is still unclear if the cause is deliberate Russian jamming or the fact that there is a lot of Russian and foreign SAR (synthetic aperture radar) satellite activity over that area and a lot of Russian military electronic systems on the ground that could deliberately or accidentally interfere with the Sentinal-1’s ability get clear images of what is down there.
This may be another side effect of the appearance of new radar satellites developed by China and several Western firms over the last few years. This has put a new generation of SAR equipped radar satellites into orbit. These SAR systems are powerful and inexpensive enough for a wide variety of commercial customers to use. The United States and European countries have at least ten of these new satellites in orbit with at least as many deployed by other nations.
Typically, a commercial firm wants SAR images over a specific area for a specific time. Whenever you see a monochrome photo in the media showing what appears to be a 3D view of the ground, it is usually from an SAR satellite. Being a radar, SAR sees through clouds and other atmospheric obstructions that plague photo-satellites. SAR can also penetrate trees and vegetation if the user wants that.
Since the 1980s SAR radars used by aircraft and UAVS have been developed that have a lot more capabilities, including greater resolution, smaller size and weight and lower cost. All SAR radars are now digital and the smallest ones are often found in the warheads of missiles where they identify and home in on targets they are programmed to find and destroy. SAR radars have also been reducing their electricity needs, which is a major item for SARs used in space satellites where sustained electric power is from solar panels.
Since 1978 satellites equipped with SAR have been in orbit. Many of the early ones were for ocean surveillance and for mapping remote land areas. These were analog and limited in capabilities and resolution. Since the 1990s a new generation of less expensive digital image SAR space satellites have emerged. A typical SAR can produce photo quality images at different resolutions. At medium resolution (objects larger than 3 meters are identifiable) the radar covers an area 40x40 kilometers. Low resolution (20 meters) covers 100x100 kilometers. Every year new or updated SAR equipment becomes available. SAR satellites operate in a LEO (Low Earth Orbit of 600-800 kilometers).
SAR satellites are often launched in groups (“arrays”) of three and they travel together to quickly take 3D photos of what is below them. With enough SAR arrays available you can put an area under persistent coverage and use the sequence of SAR images to detect movement of surface ships, mainly commercial vessels tracked for safety purposes. Over the Western Pacific several nations use their SAR satellites to detect and track warships, including diesel-electric subs when surfaced. Since 2010 China has been experimenting with such an array, using three satellites moving in formation over the western Pacific. China put their first South China Sea satellite up in 2019 and all will be in orbit by 2025. By 2030 the Chinese Navy will have 30 percent more ships than the American fleet. Those satellites, including non-SAR reconnaissance satellites with other sensors will add to that numerical superiority and make the South China Sea a very dangerous place for anyone the Chinese do not want there.
Meanwhile the growing number of commercial SAR satellites means the public will also be able to see what the Chinese and other naval powers (U.S., South Korea and Japan) in the Pacific can see with their military grade SAR satellites.