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Showing posts with label polarisation. Show all posts
Showing posts with label polarisation. Show all posts

Friday, February 19, 2021

Steering reflective space debris using polarised lasers [Scholarly Article - Advances in Space Research, available online 14 January 2021]

Title:
Steering reflective space debris using polarised lasers 
 
Authors: 
Jouni I. Peltoniemi a, Olli Wilkman a, Maria Gritsevicha, Markku Poutanen a, Arttu Raja-Halli a, Jyri Näränen a, Tim Flohrer b, Andrea Di Mira b  
 
a Finnish Geospatial Research Institute FGI, 02430 Masala, Finland 
b ESA European Space Agency, ESOC, 64293 Darmstadt, Germany
 
Published:
Advances in Space Research, available online 14 January 2021
[Open access article]

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 (, 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.

Tuesday, December 22, 2020

University of Bath, UK - Study offers insights into why inequality and economic decline drive polarisation

Title:
Study offers insights into why inequality and economic decline drive polarisation
 
Published:
University of Bath, Press Release, 15 December 2020
 
From the press release:
New research by Joanna Bryson, Hertie School Professor of Ethics and Technology and Visiting Professor at the University of Bath, Alexander J. Stewart of the University of Houston, and Nolan McCarty of Princeton University offers an explanation of why individuals might become more polarised when they experience economic inequality, and what this implies. Their article, “Polarization under rising inequality and economic decline”, was published in Science Advances on 11 December 2020.