Tuesday, November 29, 2011

The Suzaku Spacecrafts and Instruments

The Spacecraft

The Suzaku spacecraft weighs about 1,600 kg (3500 pounds) and it will be 7.1 meters (23 feet) long after the Extensible Optical Bench is extended in orbit. The five X-ray Telescopes (XRTs) and all the instruments (the X-Ray Spectrometer, the 4 X-ray Imaging Spectrometers, and the Hard X-ray Detector) will point in the same direction. This allows scientists to simultaneously study cosmic X-ray sources using the different capabilities of the various onboard instruments.

X-Ray Spectrometer (XRS)

The detectors in the X-Ray Spectrometer (XRS) are X-ray microcalorimeters. They work by monitoring the temperature of a tiny piece of silicon, and measuring the temperature rise that results when it absorbs an X-ray photon. As you might imagine, measuring the temperature increase from a single photon is fairly difficult. The detectors need to be kept extremely cold, almost to absolute zero (60 milliKelvin or 0.06 Kelvin, about -273 C, or about -460 F), requiring a complex cryogenic system which includes liquid helium and solid neon.

The XRS has a limited life of about 2.5 years before the neon and/or helium runs out. The XRS is special because, for the first time, it will provide both high spectral resolution (measuring small differences in the energies of X-ray photons) and high throughput (measuring lots of X rays) in one instrument.

X-ray Imaging Spectrometer (XIS)

There are 4 X-ray Imaging Spectrometers (XIS), each with a 1024x1024-pixel X-ray-sensitive Charge Coupled Device (a CCD, similar to what's in your digital camera, but sensitive to much more energetic light). The use of CCDs for astronomical X-ray spectroscopy was pioneered by the ASCA mission starting in 1993. The XIS has been developed by a collaboration of the Massachusetts Institute of Technology, ISAS, the University of Kyoto, and the University of Osaka. It was fabricated by MIT's Lincoln Laboratory.

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