Your garden variety telescope is usually what’s called a refracting telescope, one that uses a series of lenses to enlarge far away objects for your viewing pleasure. For backyard astronomy they work quite well, often providing a great view of our nearby celestial objects, however for scientific observations they’re usually not as desirable. Instead most large scientific telescopes use what’s called a reflecting telescope which utilizes a large mirror which then reflects the image onto a sensor for capture. The larger the mirror the bigger and more detailed picture you can capture, however bigger mirrors come with their own challenges especially when you want to launch them into space. Thus researchers are always looking for novel ways to create a mirror and one potential avenue that NASA is pursuing is, put simply, a little fabulous.
One method that many large telescopes use to get around the problem of creating huge mirrors is to use numerous smaller ones. This does introduce some additional complexity, like needing to make sure all the mirrors align properly to produce a coherent image on the sensor, however that does come with some added benefits like being able to eliminate distortions created by the atmosphere. NASA’s new idea takes this to an extreme, replacing the mirror with a cloud of glitter-like particles held in place with lasers. Each of those particles then acts like a tiny mirror, much like their larger counterparts . Then, on the sensor side, software is being developed to turn the resulting kaleidoscope of colours back into a coherent image.
Compared to traditional mirrors on telescopes, especially space based ones like the Hubble, this has the potential to both significantly reduce weight whilst at the same time dramatically increasing the size of the mirror we can use. The bigger the mirror the more light that can be captured and analysed and a mirror designed with this cloud of particles could be many times greater than its current counterparts. The current test apparatus (shown above) uses a traditional lens covered in glitter which was used to validate the concept by using 2 simulated “stars” that shone through it. Whilst the current incarnation used multiple exposures and a lot of image processing to create the final image it does show that the concept could work however it requires much more investigation before it can be used for observations.
A potential mission to verify the technology in space would use a small satellite with a prototype cloud, no bigger than a bottle cap in size. This would be primarily aimed at verifying that the cloud could be deployed and manipulated in space as designed and, if that proved successful then they could move on to capturing images. Whilst there doesn’t appear to be a strict timeline for that yet this concept, called Orbiting Rainbows, is part of the NASA Innovative Advanced Concepts program and so research on the idea will likely continue for some time to come. Whether it will result in an actual telescope however is anyone’s guess but such technology does show incredible promise.