Equipping satellites with laser-activated licence plates could help avoid collisions in space and track orbital debris, even if the craft lose power.
The number of satellites has rocketed in recent years thanks to the likes of SpaceX鈥檚 Starlink internet service, which accounts for around 60 per cent of the almost 10,000 satellites orbiting today. Many satellites identify themselves by broadcasting signals, but this can fail when satellites are close together, such as when they have just been launched on the same rocket.
Now, at the Netherlands Organisation for Applied Scientific Research and his colleagues have developed a satellite-tracking system that uses small cubic mirrors. Each mirror is equipped with light filters that reflect laser light in a unique way, serving as a licence plate (see image, below). By firing a laser at the mirrors from Earth and analysing the light reflected back, operators on the ground can identify the satellite in question.
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Silvestri and his team tested the system on Earth, rather than on a satellite in space, over a distance of 2.43 kilometres. They used four different combinations of light filters to create five licence plates. 鈥淲e could clearly see that there was a distinction between one combination and the other,鈥� says Silvestri, even when firing the laser at different angles.
Operating the system in space would mean accounting for the impact of atmospheric turbulence on the laser, but that shouldn鈥檛 be too difficult, says Silvestri.
The system could also help track dead satellites that have become space debris, says Silvestri. While many existing satellite-tracking systems require an onboard power supply, the reflectors passively respond to the lasers from Earth.
The technology could be particularly useful for satellites that are launched on so-called rideshare missions, where many small satellites are packed on the same rocket, because it can be hard to tell which satellite is which using radio signals from the ground, says at the University of Southampton, UK. 鈥淭he licence plate idea would be able to provide you with a unique physical identifier for each spacecraft,鈥� he says.
However, the satellite would have to physically pass over a ground station with a laser source, yet few facilities have one, says Lewis.
The system would also require international agreement along the lines of aircraft registration schemes. 鈥淚t鈥檚 a great idea unless somebody doesn鈥檛 want to have test spacecraft identified,鈥� says Lewis. 鈥淚鈥檓 not quite sure how you regulate that.鈥�
Communications Engineering
