Why has the United States always been considered the leader in the field of satellite reconnaissance? Is it really their technology that is unique in the world?
In fact, China has made amazing achievements in this field, especially the GF-11 satellite launched in 2020, and the resolution has reached the top level of the United States, reaching 0.1 meters. How?
For a long time, the world's highest-resolution optical reconnaissance satellites have been monopolized by the American keyhole series. The Keyhole series of reconnaissance satellites has been in operation since the sixties of the last century and has developed to Keyhole-12, but in fact the number is much more than 12. Keyhole-11 and Keyhole-12 are the most advanced models available, with Keyhole-11 being a reconnaissance satellite using a combination of optical and infrared. The Keyhole-11 is equipped with 2.31 m, 2.4 m, and 3.1 m main mirrors, which are extremely difficult to manufacture. This series of satellites has always been the "trump card" of the United States in the field of international reconnaissance.
Speaking of resolution, we have to mention the science.
The limit of resolution is the diffraction limit, which is calculated as θ = 1.22λ/D, where D is the diameter of the lens, and the larger the diameter, the higher the resolution.
Keyhole-11 uses photosensitive coupling component photography technology to transmit data using ultra-high frequency communication, but it needs to be transmitted to the ground command center through relay communication satellites.
Keyhole-12 operates in geosynchronous orbit with a resolution of about 0.1 meters. These technologies sound complicated, but in fact, they are the use of larger lenses and more sophisticated transmission technology to see the smallest details on the earth.
But the era of "hegemony" of the United States is over. In 2020, China's GF-11 satellite was launched, which was originally designed for agricultural census and disaster prevention and mitigation. However, it has a resolution of 0.1 meters, which directly challenges the technological hegemony of the United States. Behind this achievement is the continuous breakthrough of Chinese scientists in large-aperture optical lens and mirror technology over the years. Before 2020, China had successfully conquered the manufacturing technology of large-diameter optical convex lenses and mirrors.
What really makes China leap to the forefront of the world in the field of optical reconnaissance satellites is the silicon carbide mirror with a diameter of 4.03 meters developed by Changchun Optical Machinery.
This mirror not only reached the world's first-class level, but also became the largest aperture mirror in the world at that time. Speaking of this mirror, it is really the "treasure of the town" of our Chinese science and technology community.
Mirrors are very difficult to manufacture, and only a few companies in the world can do it. In order to develop this mirror, Chinese scientists have made breakthroughs in a number of core technologies.
You must know that using this mirror as the primary mirror of the reconnaissance satellite can achieve a resolution of 0.03 arcseconds, which is higher than Keyhole-11 and Keyhole-12.
Of course, the United States is not idle either, they continue to improve the Keyhole family of reconnaissance satellites. In January 2023, the United States launched the NROL-91 optical reconnaissance satellite, although the specific parameters are kept secret, it is speculated that its technical level is also quite high. However, as of June 19, 2024, the mainland's 4.03-meter silicon carbide mirror is still the world's largest aperture mirror, indicating that the United States does not currently have similar equipment. In the face of this competitive pattern, it has to be said that the competition in science and technology is like an "arms race," and no one wants to be left behind.
China's breakthrough in optical reconnaissance satellite technology is by no means just for the sake of competing in technology, but also to occupy a more favorable position in national security, scientific and technological development, and international status.
You must know that behind such scientific and technological progress is the hard work and sweat of countless scientists and engineers. They worked day and night to overcome one problem after another, and only then did they achieve today's brilliant achievements.
Just like the manufacture of this 4.03-meter mirror, it is necessary to break through the technical difficulties in materials, processes, and accuracy. For example, in terms of materials, silicon carbide must not only be light, but also extremely rigid and heat-resistant. In the manufacturing process, every step must be refined, and the slightest error will affect the final effect. This kind of craftsmanship is the source of power for China's continuous progress in science and technology.
China's achievements in optical reconnaissance satellite technology are not only a demonstration of scientific and technological strength, but also an exploration of infinite possibilities in the future.
Hopefully, in the days to come, we'll see more of these technological marvels that move the world forward. Science and technology change life, and innovation leads the future.
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