For Release: December 13, 1996

Greg Shell
Office of Media Services
(205) 544-0034

RELEASE: 96-189

TESTING BEGINS ON WORLD'S LARGEST X-RAY MIRRORS FOR NASA'S ADVANCED X-RAY ASTROPHYSICS FACILITY

The heart of a new NASA observatory designed to help answer fundamental questions about the age and size of the universe has begun five months of calibration and testing at the Marshall Space Flight Center in Huntsville, Ala.

The Advanced X-ray Astrophysics Facility's high resolution mirror assembly arrived at Marshall Nov. 30 and was installed in a special one-of-a-kind calibration facility on December 13. The largest X-ray mirror set ever assembled, it was shipped from Eastman-Kodak Company, Rochester, N.Y., where final assembly took place, to Marshall via an Air Force C-5 Galaxy aircraft.

The assembly consists of four pairs of cylindrical mirrors, precisely mounted one inside the next in a nested arrangement. The largest of the mirrors is 47.2 inches in diameter.

Calibration of the telescope mirrors will be done in two phases over the next five months. "During the first phase, the mirrors and non-flight detectors will be tested," explained Dr. Martin Weisskopf, Advanced X-ray Astrophysics Facility project scientist at the Marshall Center. "In the second phase, the complete system of mirrors and the observatory's science instruments will be tested and calibrated.

"The calibration process will verify that the telescope's mirrors are aligned and operating properly," said Weisskopf. "We will use familiar X-ray sources -- similar to dental or medical X-rays -- to measure the performance of and calibrate the mirrors under controlled conditions. Because of the telescope's superior capabilities, we must use X-rays with precisely known characteristics to determine the observatory's accuracy."

Measurements taken during the calibration process will allow scientists to correctly interpret information received from the telescope once it is in orbit.

NASA's world-class X-ray Calibration Facility at Marshall provides a space-like environment in which to test and calibrate sophisticated X-ray instruments before they are launched. The facility was extensively modified to accommodate the Advanced X-ray Astrophysics Facility.

During calibration, X-rays will be generated and directed down the X-ray Calibration Facility's 1,700-foot guide tube and into the mirror assembly situated in a vacuum chamber at the other end. Diagnostic equipment will precisely measure X-ray wavelengths and intensities.

Following calibration, the mirror assembly will be shipped to TRW Space and Electronics Group, Redondo Beach, Calif., where it will be integrated with the rest of the observatory and spacecraft.

Scheduled for launch aboard the Space Shuttle in 1998, the telescope will study X-ray sources such as black holes, quasars and the nuclei of galaxies.

"In orbit, the world's most powerful X-ray telescope will record images of never-before-seen X-ray sources," said Weisskopf. "In concert with NASA's other Great Observatories, including the Hubble Space Telescope and the Compton Gamma-Ray Observatory and the planned Space Infrared Telescope Facility, the X-ray observatory will play a key role in identifying the age and size of the universe."

The Marshall Center is managing development of the observatory for the NASA Headquarters Office of Space Science. TRW is the prime contractor for the telescope. Ball Aerospace Division, Boulder, Colo., provided hardware subsystems. The Advanced X-ray Astrophysics Facility mirrors were built and assembled by Hughes Danbury Optical Systems, Optical Coating Laboratory, Inc., Danbury, Conn., and Eastman-Kodak Company.