Fall 2002 -- Vol. 20, No. 1

Ge Receives Grants to Develop Space-Exploration Technology

Jian Ge, Penn State assistant professor of astronomy and astrophysics, has received two new grants from the National Aeronautics and Space Administration (NASA) totaling $927,000 to develop next-generation instruments and technologies to be included on future space-exploration missions designed to study new astronomical phenomena in the universe.

One of the grants, from NASA's Space Astrophysics Research and Analysis program, pledges support for three years totaling $630,000. The other, from NASA's Astrobiology Science and Technology Instrument Development program, is for one year and $297,000.

The funding supports Ge's development of technologies for NASA space missions such as the Next Generation Space Telescope and missions to Mars. One of the technologies is an infrared-silicon-immersion grating that consists of a large number of narrow, equally spaced steps etched on silicon substrates. This grating can separate infrared radiation into separate wavelengths of “colors,” much like rain droplets can serve as a prism to separate colors of the visible spectrum. Unlike raindrops, however, Ge's silicon grating is designed to have unprecedented color-separation power.

Ge's innovation is two-fold, both in using silicon for the grating to boost its color-separating power and in configuring the grating with silicon to reduce the size and weight of future instruments. “Previous technology resulted in instruments so large they took up an entire room,” Ge said. “Now, with this new silicon-immersion grating, an instrument with the same kind of performance can fit in the space of a suitcase or a computer monitor, which is very critical. Now it can fly in space.”

In addition to the infrared-silicon-immersion-grating technology, Ge and his team at Penn State are developing three-dimensional image-slicer technologies for future application in remote-sensing and surface-landing missions to Mars. Ge's image slicer will be able to simultaneously obtain image and spectral information from objects in space to greatly speed up surveys designed to detect new astronomical phenomena. Those Mars missions would center on a search for places on the planet where water and organic materials may have existed in the past or may be present today in the deep subsurface.

Other technologies that Ge and his research team have developed already have produced tangible results. For example, they developed an infrared camera with a specially shaped mask over the “pupil” of its eye to correct the circular diffraction pattern that occurs with conventional telescopes and they installed it on the 100-inch telescope at the Mount Wilson Observatory in Pasadena, California. This specially shaped pupil mask is a solid, light-blocking circle into which Ge and his team have cut a dozen strategically placed eye-shaped openings. The mask allows fainter companions to be seen around bright objects, and is an improvement over the circular masks that astronomers have been using to block the light from a bright star in an attempt to see a nearby fainter object, much like the appearance of the corona during a total eclipse of the Sun. The first time Ge and his team used their new infrared camera with its innovative optics, they discovered three small, faint stars that had never been observed before, apparently locked in the gravitational embrace of much larger and brighter companions.

Ge is continuing to develop this infrared-camera shaped-mask technique in collaboration with Ball Aerospace, Princeton University, the Harvard-Smithsonian Center for Astrophysics, and other institutions for NASA's Terrestrial Planet Finder mission, which is expected to be launched between 2012 and 2015.

Andy Elder

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