China’s heat-seeking radar with 300km range boosts anti-stealth tech, say defence scientists

Engineers say their small infrared search-and-track system can pick up the heat signature of a fast-moving aircraft from an unusually long distance. In distant target-searching mode, the radar can scan the entire sky in just a few seconds, faster than most existing heat seekers, the team says. — SCMP

Defence industry engineers in southwestern China have built a small infrared search-and-track system that can pick up the heat signature of a fast-moving aircraft from an unusually long distance, the team says.

The medium-wave infrared system has detected and tracked civil aircraft from a distance of 285km (177 miles), according to a paper published in the peer-reviewed Chinese journal Infrared And Laser Engineering on Friday.

“The outline of the target, the rotor, the tail and the number of engines can be clearly identified from the infrared spectrum image,” said the team led by Liu Zhihui, an electrooptics engineer with defence contractor Sichuan Jiuzhou Electric Group Company.

Chinese scientists developed a small but powerful heat-seeking radar with a detection range of nearly 300km that can be mounted on a car, fighter jet or satellite. Credit: Sichuan Jiuzhou Electric Group Company Limited

The heat-seeking radar can also emit a powerful laser beam to illuminate the target aircraft to gather more information, such as the number of windows on the plane, according to the researchers.

Because of its small size, the device can be mounted on a car, aircraft or even satellite for a wide range of applications, including “surveillance, early warning and (missile) guidance”, said Liu and his colleagues.

Long-distance infrared radar technology plays an important role in anti-stealth warfare.

Even as a military aircraft equipped with stealth technology can dodge traditional radar, its body and engines emit heat.

Most infrared cameras cannot see beyond a range of 20km because the relatively long infrared waves – physically equivalent to low-energy light – are easily absorbed by the atmosphere.

But some more intense heat signals in the mid-infrared range can pass through a “window” in the air and travel much farther.

China has developed a heat-seeking radar for its J-20 stealth aircraft that can pick up the signature of a US B-2 stealth bomber and an F-22 fighter from 150km and 110km away respectively, according to a report by in 2015.

Increasing the detection range of infrared radar is not easy, according to Liu’s team. Only a few photons, or particles of light, could reach the detector’s tiny lens.

Liu said their system used a cutting-edge optical sensor that could detect single photons efficiently and accurately.

The team did not give any details about the single-photon detector, but it is a field China has been known to play a leading role in recent years.

In 2016, China launched Mozi, a satellite equipped with what was then the most sensitive single-photon detection technology that took quantum communication to space for the first time.

In a quantum CubeSat launched earlier this year, Chinese scientists reportedly reduced the size of the detector to just a fraction of the original device thanks to continuous government investment to improve the technology.

The aircraft speed caused another problem, according to Liu’s team.

Infrared imaging of a civilian aircraft at varying distance. Credit: Sichuan Jiuzhou Electrical Group Company Limited

Because the infrared radar had to “stare” at the sky for a long time to detect a distant threat with an extremely weak signal, a rapidly moving target could leave behind a fuzzy image and affect the accuracy of identification and tracking.

The Chinese team said its innovation involved a fast spinning mirror inside that could effectively eliminate the motion-blur by precisely and automatically adjusting the direction of light beams.

In distant target-searching mode, the radar can scan the entire sky in just a few seconds, faster than most existing heat seekers, according to the researchers.

Liu’s team said it had tested the device in challenging environments, with temperatures varying from minus 40 degrees to 60 degrees Celsius, and its performance remained stable.

According to the researchers, the enemy would have difficulty locating the radar because it did not emit a signal while in passive mode. The device would also have a higher chance of survival in electronic warfare because it was difficult to jam infrared signals with existing technology.

Another long-range infrared radar, developed by researchers with the Chinese Academy of Sciences’ Changchun Institute of Optics, Fine Mechanics and Physics in northeastern China, detected the heat signal of an aircraft from a range of 225km, according to a scientist involved in the project.

The device also identified and tracked the International Space Station from a distance of over 1,000km on a clear night.

The effective working range of a heat radar can be affected by many factors, including weather, background temperature in the atmosphere, the viewing angle to an aircraft’s engines and heat reduction technology, according to military experts.

Countries, including China and the United States, are racing to develop next-generation infrared technology that could affect the outcome of a war.

These projects include hypersonic heat seeking missiles that can identify and strike a moving target as small as a car, and a global early warning system based on low-orbit satellites and airships that can detect the heat produced by a hypersonic weapon from thousands of kilometres away. – South China Morning Post

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