New technology helps to take pictures of microscopic objects in orbit

A team of military scientists has developed laser imaging technology that allows ground stations to identify and track targets in space with unprecedented precision.

The radar device, designed by professor Han Fei at the National University of Defense Technology in Anhui province, can capture images of objects as small as a fist in near-Earth orbit with a resolution of up to 3mm. The technology could help guide laser beams from the ground to remove small pieces of space junk that threaten satellites and spacecraft, Han and his colleagues report in the March 12 issue of the journal Acta Physica Sinica.

Space debris as small as a few centimeters is a big threat to satellites.

The problem that causes space engineers the most headache is the large piece of debris 1 - 10 cm because the satellite has a protective layer that prevents the smaller piece of junk, while the larger piece can be detected by current technology with a limited time. early enough to adjust the flight path. In 2016, one of China's largest space radar systems lost 4% of its power cable supply after debris more than 1cm long crashed into a satellite's solar cell.

High-powered lasers can cause such a small piece of debris to change its path and eventually fall through Earth's atmosphere. But the laser needs to be fired accurately with millimeter-scale errors, according to Han's research team. In low-gravity environments, most debris floats freely, making identification and tracking more difficult.

The new technology, called laser reflectance tomography, is inspired by CAT scans used in hospitals, which use several laser beams to illuminate a target surface, then reconstruct an image from the emitted light particle. in many different directions. The resolution of images taken with this method is determined by the small difference in the angle of the laser beam when it reaches the target rather than the distance from the observer. Through improving the quality of the laser source and the sensitivity of the receiver, scientists are able to obtain super-sharp images of the microscopic object at a distance.

The radar built by Han and his colleagues fires many short pulses with a maximum output of more than 100 kilowatts. Placed on the bank of a water reservoir on the outskirts of Hefei city, the device produces a very sharp image of a 5cm wide target that rotates at a distance of 1km. The results provide evidence of the device's potential use in space.

Han said that he and his colleagues developed technology based on high-end laser sources that significantly reduce noise affecting signal quality. They also developed a new algorithm using artificial intelligence to estimate the random motion of small targets, helping the radar to generate high-quality images with incomplete and rapidly changing information.