Instrument falling short on X-ray telescope

The Chandra X-ray telescope shorly after its deployment July 23

September 15, 1999
Web posted at: 2:10 p.m. EDT (1810 GMT)

(CNN) -- Engineers are trying to fix a troubled science instrument aboard NASA's recently launched $1.5 billion X-ray telescope, which has been orbiting Earth for several weeks but cannot be serviced in space.

A spectrometer aboard the Chandra X-ray Observatory recently has returned less crisp data than expected, said Harvey Tananbaum, director of the Smithsonian Astrophysical Observatory Chandra X-ray Center in Cambridge, Massachusetts.

Engineers are running diagnostics to learn more about what is degrading incoming images and how to fix the glitch.

The problem involves light-sensing chips on one side of the spectrometer, which is used for science observations.

Initially, Chandra was planned for a lower orbit around Earth, but cost constraints forced a redesign that put the telescope in a higher orbit that passed through radiation belts that can be lethal to astronauts. Chandra has no hooks or grips on it that would allow astronauts to latch on and repair it.

For that reason, Chandra failures must be fixed, if possible, remotely via computers on Earth. With the Hubble Space Telescope, astronauts fixed its defective 94-inch primary mirror in space in 1993.

As for Chandra, most experiments planned with the spectrometer can go forward using the back side of the instrument or a separate camera instrument, said Martin Weisskopf, Chandra project scientist at NASA's Marshall Space Flight Center in Alabama. Marshall oversees the mission.

The observatory was released from the space shuttle in July and returned its first images of a supernova remnant a month later.

Overall, the telescope is in excellent health and performing as expected, Weisskopf said.

Engineers and scientists recently have used the telescope to observe the Capella star system and coordinated to match those data with observations from NASA's Hubble Space Telescope, the National Science Foundation's Very Large Array radio telescope and various satellites.