Designing OPRA Glasses

University of Arkansas researchers have received a NASA instrumentation grant to build a probe for planetary rovers.
Credit: University of Arkansas

University of Arkansas researchers, in partnership with a local company will develop a probe for future planetary rovers that will help scientists study the history of the solar system by examining the properties of layers of material beneath the surface of the moon, Mars, comets and other planetary bodies.

Scientists at the Arkansas Center for Space and Planetary Sciences and officials of Space Photonics Inc. received a $403,000 grant from the Planetary Instrumentation Development branch of NASA, which will allow them to create an optical probe that can be used to determine the composition and amount of ice beneath the surface of a planetary body.

"Our intention is to deliver to NASA hardware that is ready for a mission," said Rick Ulrich, professor of chemical engineering and principal investigator for the project. This particular instrument will help researchers answer questions that have been around since planetary bodies were discovered.

"When we look out at these places, we only see the surface, and we wish we could see what lies beneath," Ulrich said. "Those layers contain the timeline of the solar system’s history."

To examine the layers, the researchers will build an Optical Probe for Regolith Analysis, an instrument they refer to as OPRA.

The instrument will operate at the base of a rover, driving a spike into the soil. The spike, which may be anywhere from one to four feet long, will contain several dozen quartz windows along its length with fiber optic cables connected to an infrared spectrometer back in the rover, which will provide spectral analysis as a function of depth. Because all the electronics will be isolated in the rover, there will be no heat source to alter the possibly frigid interior of the planetary body.

"OPRA will analyze these layers without disturbing them," Ulrich said. "We’ll get composition versus depth at every layer." The infrared spectrum will provide information on the kind of rock, its chemical composition, the amount of water in the rock and how the molecules are arranged. By looking at the compositions of different layers, the researchers can peel back time and look at the geologic history of the planetary body.

Currently spacecraft are looking under the martian surface using radar. This map shows MARSIS radar data indicating the thickness of the south polar layered deposits of Mars, with purple representing the thinnest areas and red the thickest. The total volume of ice in the layered deposits is equivalent to a water layer 11 meters deep, if spread evenly across the planet.
Credit: NASA/JPL/ASI/ESA/Univ. of Rome/MOLA Science Team/USGS

"NASA wants simple, robust and effective hardware, and OPRA is all three of these," Ulrich said. The public-private partnership with Space Photonics strengthens the university’s ability to attract major instrumentation funding.

Space Photonics has served as a research and development company for the Department of Defense and for NASA and has reported recent product sales to Honeywell, Lockheed-Martin and Orbital Sciences.

"The relationship with the University of Arkansas has been key for us," said Matthew Leftwich, a senior development specialist and lead engineer at Space Photonics, a University-based start-up company. Space Photonics will develop the fiberoptic cable interface that will carry the infrared light signals to and from the alien soil, through the sub-surface probe. Infrared light sent to and reflected back from the alien soil into the probe’s fiber-coupled interconnect system will deliver the data to the Fourier-transform infrared spectrometer for analysis.

"SPI will be collaborating with the OPRA design team to determine the optimal methods of fiber-to-quartz lens coupling and fiber routing throughout the OPRA probe," he said.

To test the instrument, the researchers will build a large sandbox-like structure that will contain a Mars soil simulant, clay or other materials that might be found on planetary bodies. They will use this and other means to test the instrument, trying to determine the force necessary to penetrate the ground, how the windows should be positioned and how many times the probe can be used before the material begins to wear. They also will compile a library of spectral results from the different materials.

"We envision that this will work on Mars, the Moon, comets and asteroids," Ulrich said. At the end of the project, the probe will be ready for NASA to consider for a mission, and it could be in space in 4 to 6 years.

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