Steering reflective space debris using polarised lasers

Abstract

Since realising the idea that a man-made object can be intentionally placed into the Earth’s orbit, almost 10,000 satellites have been launched for multiple scientific, commercial and military purposes. These activities produce a huge amount of junk comprised not only of defunct artificial objects that no longer serve a useful purpose, but various collisions, explosions and leaks have produced millions of pieces of objects of size varying from micrometers to meters. Space debris pose a threat to sustainable space and to the near-earth environment at large. As a result, there is a need for the removal of such objects in a controlled and well-planned manner, or at least safeguarding the most precious satellites from collisions. Among the proposed techniques to avoid collisions, the orbital laser momentum transfer method has good potential for altering the orbits of high area-to-mass-ratio objects (A/m≳1m2/kg, typically a few cm in size), that are too numerous for capturing techniques. The method is based on the idea of illuminating the target with a laser that induces radiation force. Here we show that the control of the debris can be further improved by using the polarisation of the laser beam. Certain amount of debris objects, maybe around 10–20%, pose asymmetric against the beam, and reflect light asymmetrically and significantly polarisation-dependent. This provides an opportunity for the closed-ended problem by introducing an additional degree of freedom for the direction of induced momentum. We present the theory for polarised light dynamics, and develop a new scattering model for reflective space debris. The model is supplemented with laboratory measurements. We show that asymmetry of the targeted object in itself may turn the momentum 1–30° for typical debris objects, and polarisation of the incident beam is capable of further affecting this direction by several degrees.