'Alice' Going to the Moon
Ocean Optics of Dunedin, Fla., has custom-engineered a spectrometer named Alice for an upcoming NASA mission to the moon’s south pole. The Lunar CRater Observation and Sensing Satellite (LCROSS) will carry the equipment to help analyze the makeup of the lunar craters, with the goal of locating water below the moon’s surface.
Working closely with Aurora Design & Technology Inc. of Clearwater, Fa., Ocean Optics is developing the reflectance viewing optics for the mission. Its QE65000 highly sensitive spectrometer was used as a platform to custom build a spectrometer to NASA’s specifications.
"Alice" will be part of NASA's mission to the moon's south pole.
The LCROSS mission will send a rocket crashing into the moon at more than twice the speed of a bullet in order to study the resulting ejecta cloud. The impact is expected to generate a 2.2-million-pound plume of matter, through which another spacecraft carrying Alice will fly, looking for signs of water and other compounds.
As the spacecraft approaches the moon's south pole, the upper stage will separate, then will impact a crater in the south pole area. A plume from the upper stage crash will develop as the Shepherding Spacecraft heads in toward the moon. The Shepherding Spacecraft will fly through the plume, and instruments on the spacecraft will analyze the cloud to look for signs of water and other compounds. Additional space and Earth-based instruments also will study the 2.2-million-pound (1000-metric-ton) plume. Then the Shepherding Spacecraft itself will become an impactor, creating a second plume visible to lunar-orbiting spacecraft and Earth-based observatories.
Aurora Design & Technology, an engineering firm and provider of domestic outsourcing, is developing the optics responsible for viewing the light scattered and reflected by the ejecta cloud as it rises into the sunlight. Two telescopes will feed this light into spectrometers for analysis of the material in the ejecta cloud.
Aurora is delivering optics for viewing out the side of the Sheperding Spacecraft which will allow scattered light from the ejected plume to be measured to determine the size and shape of the particles. The analysis of these particles will determine the makeup of the impact site as well as the crater’s spectral features. The spectral features will provide data on the chemical makeup of the impact site and the dust cloud, on impact and from reflected sunlight. The founder of Aurora Design & Technology, David A. Landis, was also responsible for the development of the ultraviolet and visible spectrometer used on the LCROSS mission as the former head of Ocean Optics' engineering department.
Alice will measure the reflectivity of the plume as it rises into the sunlight, enabling scientists to distinguish between water vapor, water ice and hydrated minerals (such as salts or clays) with molecularly bound water. With a wavelength range of 270-650 nm and an optical resolution of less than 1.0 nm, Alice will be able to identify ionized water (visible at 619 nm), OH radicals (visible at 308 nm), and other organic molecules containing carbon, with a high degree of accuracy.
The unit’s back-thinned detector makes the most of the available light -- a critical feature, since the measurements will be taken from the dark region of the moon where light is scarce. Water hidden deep in the moon’s craters could mean drinking water or even the ability to break down the hydrogen and oxygen molecules into rocket fuel, laying the foundation for the moon as a staging point for further space exploration.
To survive the harsh conditions of the lunar mission, Alice was designed to withstand extreme temperature ranges and significant shock and vibration. All of the materials, optics and mounting hardware were selected with these hazards in mind. In addition, several electronics modifications were made to accommodate conversion of the communication ports from USB to RS-422 and of the power supply from 5V to 24V. Ocean Optics said the technology is able to achieve up to 90 percent quantum efficiency (defined as how efficiently a photon is converted to a photoelectron) with high signal-to-noise and rapid signal processing speed.
With only 12 weeks to first prototype, Alice has passed pre-flight testing. It has cycled from -50 °C to +70 °C with very little change in spectral performance and passed flight qualification testing at 15-g RMS vibration and over 200-g shock.
LCROSS is set to launch in October 2008 from the Kennedy Space Center. The spacecraft will orbit the Earth twice before hitting the lunar south pole in January 2009.
Alice was named for Alice Kramden, a character on the ‘50s sitcom The Honeymooners. Alice’s husband, Ralph, was famous for repeatedly threatening to send her, "bang, zoom, straight to the moon!"
This is the second NASA collaboration for Ocean Optics. A unit designed around the company’s HR-series spectrometers will be part of the 2009 ChemCam Mars mission to study rock and soil composition on the red planet.
For more information, visit: oceanoptics.com
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