Gamma and Cosmic Ray Astrophysics

 
 
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Constellation X-ray Mission
Hard X-ray Telescope (HXT)

The Hard X-ray telescope is designed to image X-rays from <6 to >40 keV with resolution  better than 1' over a 8' field of view.  X-rays are collected by graded multilayer reflective optics and imaged with a position sensitive X-ray detector.  The mirrors have a 9 meter focal length. 

The baseline Constellation-X mission consists of 6 identical spacecraft.  Each spacecraft has 3 identical HXT instruments.  The large number of identical instruments is necessary to achieve the large collecting area of >5000 cm2  at 10 keV. 

Several technologies are under development for the focal plane detector.  CZT is a leading contender for the focal plane detector.  NRL is funded to develop two alternative detector technologies: 

  • Silicon strip detectors have heritage in spaceflight and high energy physics.  A detector configuration using silicon is under development with a useful energy range to 40 keV  (Dr. Neil Johnson, PI). 
  • NRL is also developing germanium detectors for the focal plane (Dr. Richard Kroeger, PI).  Germanium has a higher stopping power than silicon, better energy resolution than CZT (lower energy threshold), and is easily available sizes of appropriate area and thickness for HXT.   The germanium work is supported in part by Constellation-X (thermal model), NASA SR&T, NASA SBIR (electronics and fabrication), DOE (fabrication), GSFC DDF (fabrication), and ONR. 
CZT and silicon detectors would both be operated at about -20 C.   The germanium detectors must be cooled to ~80-120K. 

Please visit the Constellation-X home page  for more information. 

Back to Position Sensitive Detectors Project
last updated: 30-Sep-1998