Chinese researchers simulate lidar system that could detect US fifth-generation F-35 from over 60 km, here is how it works

A computer simulation by Chinese researchers has examined whether a missile equipped with a new single-photon light detection and ranging, or lidar, system could detect and track an F-35 stealth fighter from as far as 61.5 km (38 miles) at night, as per an SCMP report.

The research could potentially affect the assumptions around how difficult an F-35 would be to detect in an air-combat scenario, although the study does not demonstrate that such a system has been built, tested in flight or incorporated into an operational missile, as reported by SCMP.

The research was led by China Airborne Missile Academy, a research and development centre specialising in air-to-air missiles as well as their mass production. The paper was published in the peer-reviewed Chinese journal Aero Weaponry on September 18.


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How the simulated lidar system would detect an F-35C

The research focused on a missile-borne single-photon lidar designed to identify and track stealth aircraft.

Unlike conventional radar, which relies on radio waves to detect targets, lidar uses reflected laser light. The single-photon system examined in the study is designed to register extremely small numbers of photons returning from a target.

The researchers examined a system operating at a wavelength of 1,064 nanometres and modelled its performance against an F-35C under different atmospheric and lighting conditions.

To reflect the size and power limitations of equipment that could be carried by a missile, the simulation used low-power laser pulses of 1.0 millijoule and a compact 100 mm optical lens.

The mathematical model also accounted for several factors that can affect detection, including detector dead time, atmospheric transmission over 15 km, sky background noise, atmospheric backscatter and detector dark counts.

Study calculates 61.5 km detection range at night

According to the simulation, the lidar system would need a signal-to-noise ratio of 8.8 decibels, equivalent to at least 9.4 detected echo photons, to overcome atmospheric noise and achieve a target lock.

Under the modelled conditions, the maximum detection range reached 27.7 km during the day and 61.5 km at night.

At a distance of 27.7 km, the researchers said the system could produce target detail with depth accuracy of about 20 cm and transverse resolution of about 50 cm.

The study said the 1,064-nanometre wavelength was selected partly because stealth aircraft have fewer dedicated countermeasures aimed at active laser detection than they do against conventional radar and infrared sensing.

How the capability compares with F-35 missiles

The simulated detection distance is relevant to air-to-air combat because the F-35 can carry missiles designed for both short- and medium-range engagements.

For close-range combat, the aircraft can use the AIM-9X Sidewinder, an imaging infrared-guided missile reported to have a range of roughly 16 km to 32 km.

The F-35 can also carry the AIM-120D-3 AMRAAM for medium-range engagements. Conventional missile-borne radar systems, however, can face difficulties when attempting to detect next-generation stealth aircraft.

A lidar detection range of around 60 km would give a missile a longer window for tracking a stealth target. At the same time, that distance remains within the engagement range of the F-35's principal long-range air-to-air missiles, which can reportedly strike targets at distances beyond 160 km.

Analyst questions whether lidar can search a wide area

The study's results have also drawn technical scepticism over how the system would actually locate a stealth aircraft in a large volume of airspace.

One military analyst, who asked not to be identified, questioned whether a narrow laser beam could function as an early-warning search mechanism.

“The laser beam is so narrow, it probably couldn’t serve as an early-warning radar; in the early stages, it’s just a rangefinder,” the analyst told SCMP.

The concerns focus on the difference between detecting a target once its location is known and searching a vast area of sky to locate a stealth aircraft in the first place.

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Researchers plan further work on stealth detection

The paper remains a simulation-based assessment rather than a demonstration of a completed weapon system. It does not establish that the lidar has been manufactured, flight-tested or integrated with an operational missile.

Li said future research would focus on optimising photon-related parameters and improving techniques for more precise detection of stealth targets using missile-borne single-photon lidar.

The findings therefore describe a theoretical capability under specified simulated conditions, rather than confirming that an operational missile can currently detect and track an F-35 at the distances calculated by the model.