Contact: Tim Stephens (831) 459-2495;

SANTA CRUZ, CA — Scientists at the University of California, Santa Cruz, are now involved in several aspects of NASA’s Gamma ray Large Area Space Telescope (GLAST), scheduled for launch in 2005. After years of planning and evaluation of proposals, NASA announced in February the main investigations on which the project will focus.
The Santa Cruz Institute for Particle Physics (SCIPP) at UC Santa Cruz will take the lead in designing and building one of the principal components of the instrument, the silicon strip detectors used to record the direction of gamma rays. In addition, a proposal by associate professor of astronomy and astrophysics Stephen Thorsett was chosen as one of four "interdisciplinary scientist investigations" to broaden the scientific expertise involved in the project.
GLAST will explore the most energetic and violent events in the universe. Scientists will use the instrument to investigate objects such as distant galaxies powered by supermassive black holes at their centers, remnants of stars that have exploded as supernovae, and many other phenomena at the extremes of mass and energy.
GLAST will be built and used by an international collaboration involving more than 20 institutions from six countries. The Stanford Linear Accelerator Center (SLAC) will oversee the design and construction of the main instrument, with Stanford physics professor Peter Michelson as principal investigator. NASA’s Goddard Space Flight Center in Maryland is in charge of the mission as a whole, including the spacecraft that will carry the telescope.
SCIPP researchers, led by associate professor of physics Robert Johnson, have been working with SLAC for several years on a proposal for GLAST, but NASA was also evaluating a competing proposal.
"We were working under the assumption that we would do the project, but NASA’s decision formalizes it," Johnson said. "We have a complete prototype of the instrument that we’ve tested recently at SLAC, but now we have to bear down and do the serious engineering work needed for a space-based application."
The GLAST project will probe the rich variety of astronomical phenomena that emit high-energy gamma rays. Compared to existing high-energy telescopes, GLAST will have a field of view six times larger and a sensitivity more than 50 times greater. It will also be able to measure the energy of gamma rays over an unprecedented range.
Thorsett’s project will use GLAST to study gamma rays emitted by pulsars. Pulsars are the collapsed cores of massive stars left behind after supernova explosions. Spinning rapidly in deep space, a pulsar sends flashes of radiation sweeping across Earth like the beam of a lighthouse.
"Although pulsars were discovered by detecting the energy they emit in radio wavelengths, most of the energy they emit is in x-rays or gamma rays, so the energy range of GLAST is a natural place to study the physics of pulsars," Thorsett said.
He plans to combine observations from radio telescopes on the ground with GLAST’s observations to study the physics of the radiation processes in pulsars.
The design for GLAST bears little resemblance to conventional telescopes with lenses and mirrors. The primary instrument is an array of towers composed of thin lead foil interleaved with thin silicon detectors, followed by a matrix of scintillation crystals. The silicon detectors, designed by SCIPP, measure gamma ray direction, while the scintillation crystals measure the gamma ray energy.
With about 80 square meters of silicon strip detectors, GLAST will be by far the largest silicon-based detector ever launched into space, Johnson said. Joining Johnson on the project are adjunct professor of physics Hartmut Sadrozinski, several postdoctoral researchers, and a cadre of highly skilled engineers and technicians. Several UCSC undergraduates are also involved in the project.
In addition to the scientific investigations, the GLAST project includes a public education component aimed at students from kindergarten to college levels. Although the details of this component have not been worked out yet, SCIPP’s outreach programs have already brought local high school science teachers into the lab to learn about the institute’s work on silicon strip detectors.
Both the instrument itself and the phenomena to be studied make GLAST a natural vehicle for getting students interested in science, Thorsett noted. "We will be studying some of the most exotic phenomena in the universe," he said.
Editor’s notes: You may contact Robert Johnson at (831) 459-2125 or and Stephen Thorsett at (831) 459-5170 or
Additional information about the GLAST project, including images suitable for downloading, can be found at the following Web sites:
NASA’s site:
SLAC’s site: