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Moore Foundation funds detector research October 28, 2008

Posted by Sarah in random.
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Artists impression of the 30-m primary mirror of the Thirthy Meter Telescope (TMT)

Artist's impression of the 30-m primary mirror of the Thirthy Meter Telescope (TMT)

The Gordon and Betty Moore Foundation recently awarded $2.8 million to researchers at the Rochester Institute of Technology for the development of noiseless detectors in the framework of the Thirty Meter Telescope project. This is really good news for astronomers: not only is it a significant amount of money invested in a hugely important area of our science, the Foundation’s high profile helps raise awareness of the value of this work. Personally I’m happy this research is being carried out at a research institution rather than a private company, as corporate strategies are not always compatible with the “niche applications” that astronomy instruments usually are.

Charge coupled devices (CCDs), the silicon devices that are often used to record light in digital cameras, essentially convert incoming light units, or photons, into an electric charge, or electrons. The charge collected at each pixel of the detector is read out at regular intervals, and the electron counts are used to reconstruct an image. But the electronics aren’t perfect: for example, a single pixel’s response to incoming photons can vary over time, and to that of the other pixels on the array; the on-chip circuitry generates electron noise that contributes to the final signal that is read out; thermally generated electrons form a “dark current”. These and many other factors require careful calibration and post-processing of images, and ultimately limit the performance of the device, particularly in low-light applications such as imaging of faint astronomical sources.

Reducing this noise is absolutely critical to obtaining clearer, sharper images. With the Moore Foundation grant, astronomer Don Figer and his colleagues at RIT will collaborate with MIT’s Lincoln Labs to develop detectors that can record the arrival of single photons in the instrument without pesky noise for the Thirty Meter Telescope project – the US counterpart to the ESO-led European Extremely Large Telescope that is currently under way in Europe.  Instrument developers in Europe will undoubtedly be watching their progress closely!

Artists impression of the 42-m primary mirror of the European ELT.

Artist's impression of the 42-m primary mirror of the European ELT.

“You could quadruple the power of a telescope just by using this detector,” says Figer, director of the Rochester Imaging Detector Laboratory at RIT’s Chester F. Carlson Center for Imaging Science. “Or you can do the same thing by making a telescope twice the size, but then we’re talking a cost of billions of dollars and taking on a monumental engineering challenge.”

In a second stage of the project, Figer and his colleagues will turn to infrared detector technology, replacing the traditional silicon of CCDs with Indium Gallium Arsenide (InGaAs).

The sensitivity of InGaAs extends only marginally into the infrared wavelengths – the so-called near-infrared regime. In order to really peer through dust into the very core of star-forming regions, or for ultra-sensitive studies of high-redshift objects, we have to look further in the infrared, beyond 2-3 microns. An instrument called METIS is in the works to explore just this wavelength region using the 42-m European ELT, and as it happens I work on it!

The technology needed to detect this kind of infrared light is quite different to visible light CCDs. Infrared detectors are demanding and expensive to produce and have very limited commercial applications. As a result, astronomers face a continuous struggle to obtain them for their instruments. A nice grant for IR detector development would have my full support!

Image credits: TMT Observatory Corporation/ESO

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