Standard telescopes use solid mirrors to image far-away objects, but the large, complex mirrors needed for astronomy can be quite expensive and difficult to construct. Their size and weight also add to the challenges of launching a space telescope in the first place.
A concept called Orbiting Rainbows seeks to address these issues. Researchers propose using clouds of reflective glitter-like particles in place of mirrors to enable a telescope to view stars and exoplanets, according to a JPL press release. The technology would enable high-resolution imaging at a fraction of the cost.
"It's a floating cloud that acts as a mirror," said Marco Quadrelli from JPL, the Orbiting Rainbows principal investigator. "There is no backing structure, no steel around it, no hinges; just a cloud."
In the proposed Orbiting Rainbows system, the small cloud of glitter-like grains would be trapped and manipulated with multiple laser beams. The trapping happens because of pressure from the laser light - specifically, the momentum of photons translates into two forces: one that pushes particles away, and another that pushes the particles toward the axis of the light beam. The pressure of the laser light coming from different directions shapes the cloud and pushes the small grains to align in the same direction. In a space telescope, the tenuous cloud would be formed by millions of grains, each possibly as small as fractions of a millimeter in diameter.
It would also be much simpler to package, transport and deploy, than a conventional space telescope. "You deploy the cloud, trap it and shape it," Quadrelli said, according to the press release.
To test the idea, co-investigator Grover Swartzlander, an associate professor at the Rochester Institute of Technology in New York, and his students spread glitter on a concave lens in the laboratory. His team used lasers to represent the light from a double star system. They pointed the speckled mirror at the simulated stars and then used a camera to take pictures. With many exposures and lots of processing, an image of the two "stars" emerged using the glitter mirror.
"This is a major achievement," Quadrelli said, according to the press release. "This demonstrates a highly controlled experiment in which we were able to do imaging in the visible light spectrum."
The project represents a new application of "granular matter," materials such as dust grains, powders and aerosols. Such materials are very light, can be produced at low-cost and could be useful to the space exploration community. In this particular project, the "glitter" may be tiny granules of metallic-coated plastic, quartz or some other material.
Orbiting Rainbows is currently in Phase II development through the NASA Innovative Advanced Concepts (NIAC) Program. It was one of five technology proposals chosen for continued study in 2014. In the current phase, Orbiting Rainbows researchers are conducting small-scale ground experiments to demonstrate how granular materials can be manipulated using lasers and simulations of how the imaging system would behave in orbit.
