05 Jun 2008
Optical imaging technology could help astronauts to create 3D maps of planets and moons prior to landing.
Scientists in the US are developing silicon detectors that can distinguish objects on a planet's surfaces that are centimetres apart — even when the planet is hundreds of miles away. The group from the Rochester Institute of Technology hope that their device, which uses light detection and ranging (LIDAR), will help NASA spacecraft to land safely.
"Our motivation is to develop imaging detector technology capable of obtaining three dimensional maps of surfaces and atmospheric properties," Don Figer, a researcher from the Rochester Imaging Detector Laboratory, told optics.org. "The super-rich maps will be important for determining where to land on planets and moons. They will also provide a very detailed historical record of surface modification on these bodies."
Existing LIDAR detectors generally have a single pixel that has to be moved across a scene in order to build up an image. Now, however, the US team hopes that using two-dimensional arrays of LIDAR pixels will allow faster mapping and better resolution.
"We aim to develop 2D arrays of pixels up to the megapixel scale, which will provide images at higher spatial resolutions," commented Figer. "In addition, the device is very fast — responding in hundreds of picoseconds, which allows ranging resolutions in the order of centimetres."
The device will consist of a 2D continuous array of light-sensing elements connected to high-speed circuits. The new detector can be used to measure distance, speed and planetary rotation as well as atmospheric properties such as pressure, temperature, chemical composition and ground-layer properties.
"The detector works by using techniques such as differential absorption LIDAR," explained Figer. "These methods rely on the ability to measure frequency shifts, differential widths and depths of absorption features such as those observed in moving collections of water vapour or ozone."
The team will initially develop devices that can detect a broad range of UV up to 1 µm before extending the technology to cover other wavelengths. "A key problem to overcome is to implement a design that allows various types of semiconductors to be used in the light-sensitive portion of the detector," he said.
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