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June 11, 2015

NASA Funds Johns Hopkins APL Miniature Gamma-Ray Spectrometer

NASA has awarded $3 million for development of a compact gamma-ray spectrometer by the Johns Hopkins University Applied Physics Laboratory (APL) and the Lawrence Livermore National Laboratory (LLNL); APL will lead the effort. The miniature instrument, named GeMini Plus, will help reveal the surface elemental composition of planets, comets, and asteroids, information critical to understanding their formation and evolution.

“GeMini Plus will provide resource-constrained missions, such as rovers and landers, with proven gamma-ray spectroscopy technology,” said APL’s David Lawrence, principal investigator. “The instrument is based on the gamma-ray spectrometer developed and flown on the successful MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) mission, and provides the same resolution and capabilities, but reduces the size from 20 pounds (9.2 kilograms) to 4.4 lbs. (2 kg).” The goal is that the completed GeMini Plus will be able to fit in an adult human hand.

Gamma-ray spectroscopy is unique among measurement techniques in that it can infer composition tens of centimeters deep beneath a planetary body, either remotely from orbit or while sitting directly on the surface, and quantify the elements present throughout that depth. Use of this method has led to significant discoveries on the Moon, Mars, Mercury and various asteroids. For example, the MESSENGER gamma-ray spectrometer (GRS) provided the key data demonstrating that Mercury is much more abundant in volatile elements than was ever expected.

The funding, made available through NASA’s Maturation of Instruments for Solar System Exploration (MatISSE) program, will be used to develop the instrument along with methods to improve operations and better protect it from the harsh radiation environment of space. The GeMini Plus team consists of Lawrence and co-investigators John Goldsten and Patrick Peplowski (APL), and Morgan Burks (LLNL), all of whom developed and/or operated the MESSENGER GRS.

“We plan to incorporate many lessons learned from MESSENGER and hope to make this miniaturized version of the technology available to a wide range of missions,” Lawrence said. “Gamma-ray spectrometers have become crucial instruments for planetary exploration, and provide a great deal of insight into how planetary bodies operate. They reveal details of planetary formation and how planets change over time, and do so with a clear delineation of elements that is not possible with other technologies.”

Media contacts:

Geoffrey Brown, Johns Hopkins University Applied Physics Laboratory, 240-228-5618,

Stephen Wampler, Lawrence Livermore National Laboratory, 925-423-3107,

The Applied Physics Laboratory, a not-for-profit division of The Johns Hopkins University, meets critical national challenges through the innovative application of science and technology. For more information, visit

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