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Astronomical instrument adapted for down-to-earth studies

Imaging technology originally developed by NASA to study planets and stars is being focused on down-to-earth subjects - including insects and dust devils - by New Mexico State University researchers.



NMSU astronomer Nancy Chanover often uses a hyperspectral imaging system mounted on a telescope to study planetary atmospheres. Now she has teamed up with David Voelz of NMSU's Klipsch School of Electrical and Computer Engineering to build a portable version that could be used in a wide range of applications, from remote sensing of agricultural crops to the study of weather phenomena.

The imaging system is built around an acousto-optic tunable filter (AOTF), which allows the camera to take images of an object at many different wavelengths of light without having to change filters. In astronomy, these images can provide a wealth of knowledge about a planet's atmosphere, because elements of the atmosphere can be identified by their "spectral signatures," or the way they reflect or absorb light at different wavelengths across the spectrum.

Jeff Drake of NMSU's Entomology, Plant Pathology and Weed Science Department is betting that different types of insects also have distinctive spectral signatures, and he is collaborating with Chanover and Voelz to find out. The goal is a quick and accurate way to determine what insects are present in a field, and the ratio of beneficial insects to pests.

For about three years, Drake has been working on an automated insect identification system to help farmers determine how much pesticide to use on crops. Often, he said, there are enough beneficial insects present in a field to control the harmful insects without applying pesticides, but farmers can't risk the time it takes to find out.

"The traditional method is to count by hand," he said. "Typically you use an Insectavac to get four 100-foot-row samples and that might generate 10,000 or more insects. It can take weeks to count them."

Drake's efforts to date have used a digital camera to photograph insect samples and a computer software program to analyze the images and identify insects by their shape and size.

"We've been able to get about 95 percent accuracy at the genus level," he said. "One of the drawbacks is that plant material can get classified as insects by size and shape."

With spectral images of insect samples made by Chanover and Voelz, Drake will determine whether insects can be differentiated by their spectral signatures, which could be the key to a rapid and highly accurate automatic identification system.

In another field test planned for this spring, the researchers will take the portable imaging system - dubbed PHIL for Portable Hyperspectral Imaging Laboratory - out on the Jornada Experimental Range northeast of Las Cruces to try to capture spectral images of dust devils. Jim Murphy, head of NMSU's Astronomy Department, is collaborating on that experiment, which could prove useful in the design of future explorations on Mars. Murphy, whose research interest is planetary meteorology, has been a member of spacecraft instrument teams for several NASA missions to Mars, which is notorious for its dust storms.

"The hardware is far enough along that we can do these kinds of tests and trials," Voelz said. "We haven't used the camera out in the dirt before. Part of our work is to figure out how to make it more portable, rugged and robust."

In the meantime, Chanover continues to use a telescope-mounted AOTF camera in her planetary studies. The system was mounted on the 3.5-meter telescope at Apache Point Observatory last June for a study of Uranus. Next she plans to use it to analyze the atmosphere of Jupiter.

"Having images of planetary atmospheres in a huge number of wavelengths can tell you so many things," she said. "One application that we're trying to push forward is identifying the compounds that are coloring the atmosphere of Jupiter. That is an outstanding mystery in giant planet studies - we really don't know what makes the Red Spot red."

The NMSU group has a lab filled with about a half million dollars' worth of instruments and equipment provided by NASA's Goddard Space Flight Center (GSFC). When GSFC shifted away from instrument building, the contents of its instrument lab were shipped to Las Cruces with the expectation that the NMSU group would carry forward the camera development work. Chanover, who earned her Ph.D. in astronomy at NMSU, was a postdoctoral researcher at GSFC before returning to NMSU as a faculty member in 1998.

With the NASA equipment the NMSU collaborators currently are developing two AOTF cameras, one for telescope studies and the portable one for near-field imaging.

"We haven't done full calibrations yet and we don't know all of their idiosyncrasies, but we're far enough along that we can push the instrumentation work while also making discoveries with them," Voelz said.

The project, which originated in the university's Space and Aerospace Research Cluster, is an example of the kind of cross-disciplinary collaboration the cluster approach is intended to foster.