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Astronomers celebrate new Science Center for orbiting telescope

NASA Administrator Daniel Goldin joined Dr. Harvey Tananbaum (PhD '68) of the Harvard-Smithsonian Center for Astrophysics and Professor Claude Canizares, director of MIT's Center for Space Research (CSR) in marking the opening last week of the Science Center for NASA's next powerful orbiting telescope, the Advanced X-ray Astrophysics Facility (AXAF).

Mr. Goldin's remarks -- an enthusiastic flyby of 35 years of space research history -- contrasted the 1950s view of the universe as "calm, majestic and relatively peaceful" with the contemporary picture of "violent creativity," thanks to the X-ray discoveries of Institute Professor Bruno Rossi and his colleagues in 1962.

Mr. Goldin compared the revolution arising from Professor Rossi's research and the revolution now underway at NASA, which has inaugurated, with the new Science Center, a program of "getting the scientists closer to the data and closer to the spacecraft." The scientists at last week's ceremony -- many from MIT -- applauded his comments while TV crews and print reporters vied for views of the NASA chief in his black business suit and cowboy boots.

The new Science Center will house the operations control center for AXAF, which is scheduled for launch in August 1998 aboard the space shuttle. Once aloft, AXAF will join the Hubble Space Telescope and the Compton Gamma Ray Observatory as part of NASA's fleet of Great Observatories. The Smithsonian Astrophysical Observatory, together with MIT, will receive more than $150 million over 10 years for the AXAF Science and Operations Centers under the direction of the Marshall Space Flight Center in Huntsville, AL.

Dr. Tananbaum is director of the AXAF Science Center. Professor Cani-zares is deputy director of the Center, which will control the flight operations, mission planning, data processing and user support for the AXAF mission.

"AXAF is going to be a major astronomical instrument for studying the universe, and we are delighted that MIT has contributed half the scientific instruments and will also have a significant role in the scientific operations of this national facility," said Professor Canizares.

AXAF itself is 45 feet long with a 64-foot wingspan when fully deployed. It weighs more than five tons and has an on-orbit life expectancy of at least five years. Its telescope system is a high-resolution mirror assembly with an outer diameter of 1.2m, comprised of four pairs of grazing-incidence mirrors polished to angstrom smoothness and coated with iridium.

AXAF science instruments include the Charged-Coupled-Device Imaging Spectrometer (ACIS), which provides imaging and spectroscopy; a high-resolution camera; a high-energy transmission grating (HETG); and a low-energy transmission grating.

Both the HETG and ACIS are state-of-the-art instruments developed and built at the Center for Space Research. Professor Canizares is the principal investigator for the HETG, which consists of periodic nanostructures pioneered by Professor Henry I. Smith of electrical engineering and computer science and Dr. Mark Shattenburg of CSR and fabricated by a team of CSR scientists and engineers. ACIS was developed in collaboration with Pennsylvania State University and Lincoln Laboratory under deputy principal investigator Dr. George Ricker and project scientist Dr. Mark Bautz of CSR.

The data gathered by AXAF instruments will be transmitted back to Earth, reaching the operations control center via NASA's deep space network in Spain, Australia and Owens Valley, CA. The center will relay commands to the orbiting telescope via the same network.


X-rays emanate from a large group of different astrophysical sources, including the Sun, remnants of supernova explosions, neutron stars, hot intergalactic gas, quasars and black holes.

Unlike the Hubble telescope, an optical device that operates on the visible light spectrum, AXAF will measure X-rays released by numerous cosmic events. Some of these cannot be detected visually but do reveal a variety of energetic phenomena. "Dark matter," for example, cannot be detected except by tracing the X-rays emitted by its hot gases. Some theorists believe that the superdense dark matter could one day stop the expansion of the universe due to its gravitational power.

AXAF will also be able to peer farther in at the material falling into black holes than Hubble can.

MIT has played a key role in X-ray astronomy ever since the X-ray window on the heavens was opened by late Institute Professor Emeritus Bruno B. Rossi and his colleagues. For example, MIT built the entire scientific payload of X-ray sensors in the satellite SAS-3, which operated in the mid-1970s and was controlled from MIT under the direction of Professor George Clark on a round-the-clock basis.

MIT scientists under Professor Hale Bradt are now helping to operate the Rossi X-ray Timing Explorer, named by NASA for Professor Rossi after it was launched in December 1995 to study the complex temporal variations of X-ray sources.

The last US focusing X-ray telescope, the Einstein Observatory, was launched in 1978 and functioned extremely well for three years. It also carried an MIT spectrometer designed by Professors Clark and Canizares. AXAF, the US follow-on to the Einstein Observatory, will have the ability to observe tiny 0.5 arc-second features -- 10 times better than its predecessor's resolution.

AXAF will be placed in an elliptical high-earth orbit allowing uninterrupted observing intervals of at least 48 hours. The operations center, which will operate around the clock beginning next summer, is located in space leased by the Draper Lab and designated as MIT Building NE80.

A version of this article appeared in MIT Tech Talk on September 17, 1997.

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