Chuck Bednar for redOrbit.com – @BednarChuck
Typically, glitter is something that you expect to find in a grade-school classroom, but the small, flat reflective particles are serving as the inspiration for a new type of reflective mirror that could help NASA develop a low-cost new type of space telescope mirrors.
Those telescopes, the US space agency explained, use solid mirrors to image far-off objects, but the large and complex surfaces typically used to take images can be expensive and very difficult to make. Glitter-like substances could provide a lower-cost, easier to use alternative.
Inside the Orbiting Rainbows concept
Scientists at the NASA Jet Propulsion Laboratory in Pasadena, California are working on a new experimental concept known as Orbiting Rainbows which would use clouds of reflective glitter-like particles in place of mirrors to enable telescopes to view stars and exoplanets.
That technology, principle investigator Marco Quadrelli and his colleagues explained, would enable high-resolution imaging at a fraction of the cost. He describes it as “a floating cloud that acts as a mirror…There is no backing structure, no steel around it, no hinges; just a cloud.”
In their proposed system, the JPL team would trap and manipulate the cloud of glitter-like grains using several laser beams. The pressure from that beam would generate two forces: one which would push particle away, and one that pushes them towards the axis of the light beam. Since the pressure from the laser light comes from different directions, it shapes the cloud and pushes the particles to align in the same direction, causing them to become trapped.
Millions of grains, some less than a millimeter in diameter, would be used to form the cloud in a space telescope. This would enable to instrument to have a wide adjustable aperture, or the space through which light passes during an optical or photographic measurement. In fact, Orbiting Rainbows could result in larger apertures than current space telescopes, while also being easier to pack up, transport and deploy than its conventional counterparts.
Early ground-based experiments prove promising
The light-scattering and focusing properties of natural phenomena such as rainbows and comet tails have contributed to the project, according to NASA. The concept for a telescope based on a laser-trapped mirror dates back to a 1979 paper by astronomer Antoine Labeyrie at the College de France in Paris, and the Orbiting Rainbows team is looking to make it a reality.
Currently, they are looking for ways to manipulate and maintain an orbiting cloud’s shape using laser pressure, which would enable it to function as an adaptive surface that has electromagnetic characteristics which would be useful in the optical or radar bands. Since the glitter cloud would not be a smooth surface, it would produce images with more speckled distortion than those taken using a regular mirror, but the JPL team is search for improvements.
The researchers are currently developing algorithms to take multiple images and computationally remove the speckle effect from the glitter. During a recent test of the concept, Orbiting Rainbows co-investigator and Rochester Institute of Technology professor Grover Swartzlander and a team of students spread glitter and a concave lens and used lasers to represent the light from a double star system. They then used a camera to take pictures using the instrument.
The glitter mirror system produced an image of the two mock-stars, which Quadrelli hailed as “a major achievement.” He added that their work “demonstrates a highly controlled experiment in which we were able to do imaging in the visible light spectrum,” and while it has not been tested in space, the team has been exploring reflective, refractive and diffractive versions of a telescope based on Orbiting Rainbows, with maximum sensitivity to a single frequency.
Orbiting Rainbows is currently in Phase II development through NASA’s Innovative Advanced Concepts (NIAC) Program, and represents a new use of “granular matter” in the advancement of space exploration technology. In its current phase, the developers are conducting small-scale ground-based experiments to show how they could help manipulate lasers and simulate how the imagine system would behave in low-Earth orbit.
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