NASA's Jet Propulsion Laboratory publishes news of a proposed technique to use a cloud of laser-controlled glitter to work as a space telescope for imaging exoplanets. It's called Orbiting Rainbows. We approve.
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. 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.
Such a telescope would have a wide adjustable aperture, the space through which light passes during an optical or photographic measurement; in fact, it might lead to possibly larger apertures than those of existing space telescopes.
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.
Nature is full of structures that have light-scattering and focusing properties, such as rainbows, optical phenomena in clouds, or comet tails. Observations of these phenomena, and recent laboratory successes in optical trapping and manipulation have contributed to the Orbiting Rainbows concept. The original idea for a telescope based on a laser-trapped mirror was proposed in a 1979 paper by astronomer Antoine Labeyrie at the College de France in Paris.
Now, the Orbiting Rainbows team is trying to identify ways to manipulate and maintain the shape of an orbiting cloud of dust-like matter using laser pressure so it can function as an adaptive surface with useful electromagnetic characteristics, for instance, in the optical or radar bands.
Because a cloud of glitter specks is not a smooth surface, the image produced from those specks in a telescope will be noisier — with more speckled distortion — than what a regular mirror would generate. That's why researchers are developing algorithms to take multiple images and computationally remove the speckle effect from the glitter.
More on the story here: "Glitter Cloud May Serve As Space Mirror" [jpl.nasa.gov]