NASA's Dawn mission, ready for launch Thursday from Cape Canaveral, Florida, carries an instrument ready to determine the elemental composition of the asteroid belt. The Los Alamos National Laboratory device, called GRaND (Gamma Ray and Neutron Detector), is set for an 8-year, 3.2-billion-mile odyssey to explore Vesta in 2011 and Ceres in 2015.
The Los Alamos device is one of three science payload instruments on board, accompanying a visual and infrared spectrometer and a framing camera, the mission's scientific imaging system. GRaND will measure the elemental composition of the asteroids' surfaces using high-resolution spectroscopy and neutron detection. Radiation detected by GRaND is made by radioactive decay and cosmic ray interactions with the surfaces.
Dawn will be the first spacecraft to orbit two targets. At least 100,000 asteroids inhabit the asteroid belt, a reservoir of leftover material from the formation of our solar-system planets 4. 6 billion years ago. Dawn also will be the first satellite to tour a dwarf planet. The International Astronomical Union named Ceres one of three dwarf planets in 2006.
"GRaND will help us understand processes that shaped the surface of Vesta and Ceres, such as volcanism and aqueous alteration, providing new insights into how the asteroids evolved," said Tom Prettyman, lead scientist for the Los Alamos instrument and Dawn coinvestigator.
The GRaND instrument is designed to measure the chemical composition of the surfaces, mapping the near-surface abundance of major rock-forming elements, long-lived radioactive elements, and volatiles such as hydrogen, carbon, nitrogen and oxygen, which are the major constituents of ices. The gamma-ray spectrum provides a fingerprint of the elements within the surface that can be analyzed to determine their abundance. The neutrons provide information about light elements, such as hydrogen and carbon, as well as strong thermal neutron absorbers, such as iron, titanium, chlorine, gadolinium, and samarium.
Using proven technology from Lunar Prospector and 2001 Mars Odyssey missions, GRaND also includes new sensor technologies to improve the accuracy of elemental abundance measurements. The instrument can measure many rock-forming elements on Vesta and Ceres, in addition to its ice-analysis capability. From a circular, polar mapping orbit, GRaND will map the abundance of these elements over the entire surface of Vesta and Ceres.
As described by NASA, Dawn's goal is to characterize the conditions and processes of the solar system's earliest epoch 4.5 billion years ago by investigating in detail the massive asteroid Vesta and the dwarf planet Ceres. They reside between Mars and Jupiter in the asteroid belt. Scientists theorize these were budding planets never given the opportunity to grow. However, Ceres and Vesta each followed a very different evolutionary path during the solar system's first few million years. By investigating two diverse asteroids during the spacecraft's eight-year flight, the Dawn mission aims to unlock some of the mysteries of planetary formation. Dawn will be the first spacecraft to orbit an object in the asteroid belt and the first to orbit two bodies after leaving Earth. Recent images taken by NASA's Hubble Space Telescope raise further intriguing questions about the evolution of these asteroids.
The Dawn mission to Vesta and Ceres is managed by JPL for the NASA Science Mission Directorate in Washington. The University of California Los Angeles is responsible for overall Dawn mission science. Other scientific partners include Los Alamos National Laboratory, New Mexico; German Aerospace Center, Berlin; Max Planck Institute for Solar System Research, Katlenburg, Germany; and Italian National Institute of Astrophysics, Palermo. Orbital Sciences Corporation of Dulles, Va., designed and built the Dawn spacecraft. The NASA Launch Services Program at Kennedy Space Center and the United Launch Alliance are responsible for the launch of the Delta II.
Additional information about Dawn is online at http://dawn.jpl.nasa.gov.
For imagery of Ceres and Vesta, see http://hubblesite.org/news/2007/27 online.
Los Alamos National Laboratory, a multidisciplinary research institution engaged in strategic science on behalf of national security, is operated by Los Alamos National Security, LLC, a team composed of Bechtel National, the University of California, The Babcock & Wilcox Company, and the Washington Division of URS for the Department of Energy's National Nuclear Security Administration.
Los Alamos enhances national security by ensuring the safety and reliability of the U.S. nuclear stockpile, developing technologies to reduce threats from weapons of mass destruction, and solving problems related to energy, environment, infrastructure, health, and global security concerns.