BU Today


BU astronomer lands $9.5M contract to measure charged particles near the moon

Astronomy Professor Harlan Spence is developing key instrumentation for NASA’s Lunar Reconnaissance Orbiter, which is scheduled to orbit the moon for about a year beginning in 2008. Artist’s rendition courtesy of NASA

This story was printed in the BU Bridge on January 28, 2005.

NASA scientists and engineers know that spacecraft traveling to the moon in a few years will need to be outfitted with special protection against charged particles that routinely traverse the cosmos at nearly the speed of light. But they don’t know how much protection will be necessary because the robotic and manned missions that President Bush mandated last year will last longer than previous moon trips, exposing astronauts and their high-tech equipment to more of the powerful particles.

Harlan Spence, a CAS and GRS astronomy professor and department chairman, was chosen by NASA recently to help solve that problem. An instrument he has proposed developing, called Cosmic Ray Telescope for the Effects of Radiation (CRaTER), will be among the key data-gathering tools aboard NASA’s robotic Lunar Reconnaissance Orbiter (LRO) craft, which is scheduled to orbit the moon on a one-year exploratory mission beginning in 2008. Spence (CAS’83) expects to receive an approximately $9.5 million contract from NASA for CRaTER, one of six high-profile research projects NASA announced funding for in December, as part of its LRO program. Together, the six projects will develop the instruments LRO uses to gather information that will guide the planning and execution of future lunar missions.

“The objective of CRaTER is to determine the effects on humans of long-term exposure to charged particles — mainly protons and electrons — using a material that replicates human tissue, as well as the effects on electronic and computer equipment,” says Spence, an expert on space weather and technologies that measure high-energy charged particles in space. “For decades, we’ve had a pretty good idea what types of protection are needed for short visits to the moon, but we’ll be studying what’s needed to essentially live there.”

Spence’s research team includes Larry Kepko, a senior research associate at the Center for Space Physics, as well as scientists at the California-based research group the Aerospace Corporation, MIT’s Center for Space Research, the University of Tennessee at Knoxville, the Air Force Research Laboratory in Bedford, Mass., and the National Oceanic and Atmospheric Administration’s Space Environment Center in Boulder, Colo.

CRaTER will measure the effect on human tissue and electronic equipment of charged particles called galactic cosmic rays, which often originate in supernovas and race through deep space more or less constantly, and the similar but more intense solar cosmic rays, which are caused by storms on the sun. It was a series of solar events that in late 2003 sent billions of tons of charged gas hurtling through our solar system at speeds of up to five million miles per hour, disrupting satellites and ripping apart a sizable portion of the Mars atmosphere. Astronauts aboard the International Space Station at the time could have been injured had they not taken cover in a special shelter. Spence says that much more must be learned about the effects of charged particles before stations can be designed that are safe for the moon.

“The effects of charged particles are much more severe on the moon than in the upper regions of Earth’s atmosphere, where the Space Shuttle often operates, for example,” Spence says. “That’s because a planet’s strong magnetic field deflects most charged particles before they reach the planet’s atmosphere, while particles that do get through are absorbed by the atmosphere. The moon has neither a magnetic field nor an atmosphere.”

The scientific technology at the heart of CRaTER is a novel particle sensor system that is attached to analog and digital electronics; data will be relayed back to Earth through the LRO spacecraft’s communication system. CRaTER employs a stack of detectors housed in a structure of aluminum and special material known as “tissue-equivalent plastic” that was designed for biomedical research and will help characterize the biological effects of radiation in deep space.

“In 1971, I stood with my family among the throngs that watched Apollo 15 thunder into space from Cape Canaveral,” says Spence, who has taught at BU since 1993. “It was a defining moment for me, hooking me on a career in astronomy and space science. With CRaTER, I get to relive that excitement as a space scientist — and get to experience my own voyage, of sorts, to the moon.”

Other research projects selected by NASA to develop instruments for LRO are centered at Goddard Space Flight Center in Greenbelt, Md., Northwestern University in Evanston, Ill., the Institute for Space Research and Federal Space Agency in Moscow, the University of California at Los Angeles, and the Southwest Research Institute in Boulder, Colo.