By Elizabeth Myers
New Mexico State University engineers and astronomers have teamed up to get a better look at the colors of Jupiter and Saturn.
David Voelz and Robert Hull, both in the electrical engineering department, worked with Nancy Chanover and Paul Strycker of the astronomy department to capture images of the planets using an astronomical imaging sensor, the NMSU Acousto-optic Imaging Camera (NAIC), developed by Voelz and Chanover.
The camera is based on an acousto-optic tunable filter, which can be tuned electronically.
“It’s different than a normal photographic camera,” Voelz said. “Photographic cameras use fixed filters; you can take the filter off, put a different one on, or change them with the help of a filter wheel mount, but this is continuously tunable.”
An acousto-optic crystal receives a radio frequency signal, which is tuned to select what the crystal will let through.
“The filter allows only a narrow band of light to pass, so you can tune through the colors,” Voelz said. “The crystal in the NAIC system can be tuned to pass a band of light anywhere from ultra-violet wavelengths through near-infrared wavelengths.”
This type of filter is not entirely new; one of its most common applications is for use in laser light shows, Voelz said. However, this filter is large enough for planetary imaging.
A grant from the National Science Foundation allowed the group to take the photos using the AdvancEd Electro-Optical System (AEOS), a 3.67-meter telescope owned by the Department of Defense and housed by the Maui Space Surveillance System in Hawaii.
The purpose of the observations was to study the colors of the planets to determine their chemical makeup.
“What we try and do is take pictures of the planets at lots of different color bands. Then we try and figure out what chemicals must be in the atmosphere,” Voelz said.
The astronomers decide the important things to look for and the engineers get the camera ready to make the right kinds of measurements.
“If you look in all these different colors,” Chanover said, “they correspond to different absorptions by certain constituents of the atmosphere. So if you look across the whole planet, you see where they are located across the planet.”
“One of the main reasons we do this, for Jupiter in particular, is people still don’t really understand what causes the different colors. We’re trying to address that question,” Chanover said.
The AEOS telescope is ideal for planetary imaging.
“It has a tilt tracking system that stabilizes the image, and it also has an adaptive optic system that works to correct the changes in the atmosphere due to turbulence, the twinkling that you see in the stars.” Voelz said.
The telescope is a 90-minute drive up Haleakala, a volcanic peak. “We would come up in the early evening, watch the sunset over the mountain and then take pictures of the planets through the night. It’s a great experience,” Voelz said.