FLEXIBLE plastic telescopes launched from microsatellites could serve as quick replacements for space observatories taken out by solar flares, or spy satellites downed by military action.
The telescopes, which are being developed by and colleagues at the US Air Force Academy in Colorado Springs, rely on an imaging device called a photon sieve. Traditional telescopes use lenses or mirrors to focus light by refraction or reflection, but the photon sieve uses diffraction instead. The sieve is an ultra-thin plastic disc perforated by millions of microscopic holes, each of which bends light at different angles to create a focal point.
Less light reaches the focal point compared with traditional lenses or mirrors, making it hard to image dim objects, and the device can only take black-and-white pictures. But the sieve is cheap, lightweight and easy to manufacture at large sizes. It can also be tightly folded and unfurled without being damaged. 鈥淵ou can鈥檛 do that with mirrors or lenses,鈥� says Andersen, who hopes to launch a device into orbit in 2014.
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The planned 20-centimetre-diameter telescope will be scrunched up inside a CubeSat, a microsatellite just 10 脳 10 脳 30 cm, designed for cheaply carrying small payloads. Andersen鈥檚 team aims to take pictures of the sun to prove that the concept works. A similar device could also help the search for Earth-like planets, Andersen says, though such images would require a big telescope, and would likely be just a few pixels wide.
The US Defense Advanced Research Projects Agency is also interested in using the concept to build a 20-metre version of the photon sieve for imaging objects on the ground at sub-metre resolutions.
Andersen says the design is partly a response to China鈥檚 demonstration in 2007 of an anti-satellite missile. 鈥淭hat showed a billion-dollar national asset could be shot down at any time,鈥� he says. He will present the research at the in Baltimore, Maryland, next month.
Marek Kukula of the in London says that while the devices won鈥檛 replace the likes of the Hubble or James Webb space telescopes, a 鈥渃heap and cheerful鈥� alternative to smaller telescopes would have many applications.
