GAMMA-RAY TELESCOPE TO SLEUTH FOR ORIGIN OF ELEMENTS

by Goddard Space Flight Center

The International Gamma-ray Astrophysics Laboratory (INTEGRAL), a space-science mission led by the European Space Agency, launched successfully on October 17, 2002, from the Baikonur Cosmodrome in Kazakhstan aboard a Russian Proton rocket. The satellite will now undergo system checks for two months before attaining first light.

INTEGRAL's primary goals include mapping the radioactive remains of exploded stars, detecting matter-antimatter collisions in our Galaxy's core and around black holes and neutron stars, and detecting gamma-ray bursts.

"INTEGRAL detects a form of light invisible to our eyes to peer into places in the Universe where new elements are being created, elements of which we and all things around us are made," said Dr. Bonnard Teegarden of NASA's Goddard Space Flight Center in Greenbelt, Md., the NASA Project Scientist for the INTEGRAL mission. "This powerful new observatory is a successor to instruments aboard NASA's Compton Gamma-Ray Observatory, the landmark gamma-ray astronomy mission of the 1990s."

INTEGRAL detects gamma rays, the most energetic form of light, far more powerful than optical light, ultraviolet radiation and X rays. INTEGRAL's instruments are sensitive to the lower-energy and medium-energy gamma rays within the very wide swath of gamma-ray energies on the electromagnetic spectrum.

The new gamma-ray mission will study the process of how the atoms, from which humans and all that we touch are made, were initially created in stars and stellar explosions. Hydrogen and helium, the two lightest elements, were created in the Big Bang, the primordial explosion of space that created all matter and energy in the Universe. Virtually all other elements, such as carbon, oxygen, and gold, were cooked and fused from hydrogen and helium by stars.

INTEGRAL detects the presence of elements from star explosions that emit gamma rays as the elements decay. Scientists can use this information to reconstruct the physics of how the star exploded. This will help determine the history of star formation and the lifecycle of matter and energy in the Universe. The detection of certain forms, or isotopes, of aluminum and titanium and other elements can also be used to date star explosions, analogous to carbon-14 dating.

The observatory will also detect the presence of antimatter in the Milky Way galaxy, the result of particle decay that provides yet more clues to the origin and fate of matter, including dark matter, the mysterious dominating form of matter in the Universe.

Peering at neutron stars and black holes, INTEGRAL will detect gamma rays emitted as matter heats to extreme temperatures as it swirls around these objects at high speeds. Antimatter in the form of positrons (anti-electrons) is likely produced by strong magnetic fields around neutron stars and black holes as well. Detecting gamma rays from the annihilation of antimatter with matter will help determine the physics of these fantastic objects.

Gamma-ray bursts, the most powerful explosions known in the Universe, remain a mystery. INTEGRAL is expected to detect about one burst each month and to provide prompt alerts to the ground-based observer community, which will permit rapid follow-up observations and offer clues to the nature of these explosions.

NASA is contributing to the INTEGRAL mission in several important areas. Scientists at Goddard have developed software for the calibration of the satellite's spectrometer instrument and the analysis of its data. A team of scientists at the University of California's Berkeley and San Diego campuses has provided a key background suppression system for the spectrometer that will substantially enhance its capability for detecting the faintest gamma-ray sources.

In addition, Goddard will provide an INTEGRAL data center for U.S. scientists. The latter will be responsible for administering a guest observers program for US scientists participating in this ESA-led mission and will oversee research grants to US scientists to analyze and interpret INTEGRAL data.

INTEGRAL carries four main instruments: an imager (Imager on Board the INTEGRAL Satellite, "IBIS"), a spectrometer (Spectrometer on INTEGRAL, "SPI"), an X-ray monitor (Joint European X-ray Monitor, "JEM-X"), and an optical camera (Optical Monitoring Camera, "OMC"). All four instruments are co-aligned and will observe the same region of the sky simultaneously. This allows for the clear identification of gamma-ray sources, a crucial feature in studying high-energy processes in the violent Universe.

All instruments are provided by large collaborations encompassing many scientific institutes in the ESA member states, the United States, Russia, Czech Republic, and Poland.

The INTEGRAL spacecraft weighs 4,100 kilograms (4.5 tons), and stands 5 meters (16.4 feet) high with a diameter of 3.7 meters (12.1 feet). Its eccentric 72-hour orbit will be inclined 51.6 degrees to the equator, with the closest point 10,000 kilometers above the Earth, and the most distant point 153,000 kilometers away. The spacecraft will spend most of its time beyond Earth's radiation belts to minimize background radiation effects.

For more on the INTEGRAL mission, visit their web site at: http://sci.esa.int/home/integral/