Space debris, also known as space junk, is a collection of objects in orbit around the Earth consisting of expired spacecraft, bodies of old launchers, and fragments from missiles and satellite explosions. As the orbits of these objects often overlap with the trajectories of newer objects, debris is a potential collision risk for operational spacecraft. For small particles of 1mm or less (the vast majority of the tens of million orbiting pieces), this risk can be partially mitigated by protection shields. Nevertheless, some parts on a spacecraft cannot be protected in this manner, including solar panels or optical devices such as telescopes, cameras and star trackers. For bigger pieces, the risk is partially mitigated by tracking the orbit of the space debris and manoeuvring the spacecraft to avoid actual collision.
Currently the North American Defence Command (NORAD) tracks a lot of debris via radar and maintains a debris database. But radar does not always provide sufficient accuracy to prevent a collision. A lot of major impacts have been recorded including, most recently in 2009, the destruction of an operational Iridium communication satellite after a collision with a spent Russian Kosmos rocket body. Given that space debris is a major concern for the launch of new spacecraft, there is an increasing interest from space industry actors in methods to limit generation of debris, improve debris tracking accuracy, and destroy in-flight debris.
Using the reflection of laser light to measure the distance of space debris from a ground-based station is one way to improve debris tracking accuracy. The ultimate performance of this technology relies on the ability to focus a laser beam accurately on the space debris. Therefore, the further away and the smaller the debris, the bigger the technical challenge.
The Adaptive Optics Demonstrator project is a partnership between Electro Optic Systems (EOS) and the Research School of Astronomy and Astrophysics. It aims to push laser tracking of space debris to a new level by using an ultra-fast Adaptive Optics system and a Laser Guide Star. This cutting-edge adaptive optics system will counteract the unintended effects of atmosphere turbulence in the fast-moving line of sight of a space object orbiting at 28 000 km/h over our heads.
The laser tracking system will be accommodated in the EOS Space Research Centre facility at Mount Stromlo Observatory, using its 1.8 metre telescope. Financed through additional funding contributions, the system will be upgraded with an additional high-power laser in order to conduct experimental modification of the debris’ orbit by photon pressure.