Australian National University (ANU) researchers are finding new uses for laser-based technology that sharpens telescope images – so-called adaptive optics – and potentially helps alleviate the world’s growing problem of space debris. Specially designed lasers could give decaying satellites a slight “squeeze” of photons and give just enough energy to alter the orbit of the debris and prevent an impending collision.
Lasers have a long history in astronomy. Telescopes in space like Hubble can capture spectacular images because they don’t have to deal with atmospheric distortion (the effect that causes stars to “twinkle” in the night sky). Space telescopes, however, can only be so big that ground-based observatories can offer much more eyesight with a little help from adaptive optics.
ANU professor Celine D’Orgeville explains: “Without adaptive optics, a telescope sees an object in space like a clump of light. This is because our atmosphere distorts the light that moves between the earth and these objects. However, with adaptive optics, these objects will be easier to see and their images will be much sharper. In essence, the adaptive optics cut off the distortion in our atmosphere and ensure that we can clearly see the incredible images our powerful telescopes are taking. “
Celine D’Orgeville with the 1.8-meter EOS telescope at Mount Stromlo Observatory, which tracks and images satellites using adaptive optics. Photo credit: Celine D’Orgeville / The Australian National University.
The system shines a powerful laser in the sky and excites particles in the sodium layer, which is located near the edge of space (the layer is created by burning meteorites). The excited sodium atoms appear to the telescope like a bright artificial star – bright enough to measure how the atmosphere distorts the light on the way back to the telescope. With this information, the telescope’s mirror can be easily deformed to compensate for the atmospheric effects. This has to happen thousands of times per second to keep up with the ever-changing atmospheric conditions.
This technique works well for observing distant stars and galaxies that are slowly moving across the sky. However, ANU researchers have improved the technology to track fast moving satellites and space debris.
If a piece of space junk is on a collision course with another object (which is more common than thought), an adaptive optics tracking laser could guide a secondary infrared laser to the target, pushing the junk onto a different trajectory. A system of these lasers around the world could prevent catastrophic collisions from occurring.
A representation of objects in orbit. Approximately 95% of the objects are debris in orbit and not working satellites. Photo credit: NASA.
However, such a system is politically challenging. In addition to technological improvements, innovations in regulation and international space law may be required. Misuse of trajectory altering lasers could create a diplomatic swamp, although the benefits of global cooperation on space debris are evident. If we’re lucky, ANU’s research could be the catalyst for new collaborative regulations in this area.
The ANU’s research also has a value in the area of communication. A commercial partner of the research program, Electro Optic Systems (EOS), hopes to use the system to develop laser-based communication between satellites and the ground.
Across the board, adaptive optics make lasers one of the most useful tools we have in space exploration, and their future, pardon the pun, looks promising.
Further reading:
Selected image: Artist’s impression of the extremely large telescope. Photo credit: ESO / L. Calçada.
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