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        Summary 
        
         
          
           | Description | 
           
             English: The High Energy Focusing Telescope (HEFT) is a balloon-borne instrument carrying one of the first focusing telescopes for the hard X-ray band (20–70 keV). It makes use of tungsten-silicon multilayer coatings to extend the reflectivity of nested grazing-incidence mirrors beyond 10 keV. HEFT has an angular resolution of 1.5 arcminutes in half-power diameter, and an energy resolution of 1.0 keV full width at half maximum at 60 keV. HEFT was launched for a 25-hour balloon flight on May 2005. The instrument performed within specification, and observed Cyg X-1, the Crab Nebula. 
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           | Date | 
           10 January 2008 | 
          
          
           | Source | 
           High Energy Focusing Telescope (HEFT), NASA's Scientific Ballooning Program | 
          
          
           | Author | 
           CM Hubert Chen, Fiona A. Harrison, Principal Investigator, Caltech Charles J. Hailey, Columbia Principal, Columbia, Finn E. Christensen, DSRI Principal, DSRI, William W. Craig, Optics Scientist, LLNL, Stephen M. Schindler, Project Manager, Caltech | 
          
          
           Permission ( Reusing this file) | 
           
             Images produced by NASA are usually free of copyright [...] 
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        This is the Crab Nebula in various energy bands, including a hard X-ray image from the HEFT data taken during its 2005 observation run. The angular resolution of HEFT is about 1.5′. Each image is 6′ wide.
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