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Imaging high-energy astrophysical sources using Earth occultation

Naturevolume 366pages245247 (1993) | Download Citation

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Abstract

HIGH-ENERGY astrophysical sources can be difficult to image. Photons with energies above 5 keV are hard to focus, so experiments usually employ coded masks1–4 or moving collimators5–9 to modulate the flux received by the detectors; the resulting signals are then deconvolved to form the images. Here we demonstrate a new approach which makes use of the large-area, non-collimated detectors of the Burst and Transient Source Experiment on the Compton Gamma-Ray Observatory. As the spacecraft moves in its orbit, the Earth itself acts as a stable occulting disk. Changes in the measured signal during a single occultation correspond to the integrated intensity of sources positioned along the arc described by the Earth's edge (limb). The low-altitude, moderately inclined orbit of the spacecraft ensures that the angle at which the limb traverses a source region varies between occultations, and thus data from a series of occultations can be transformed into an image. This imaging process is conceptually and mathematically similar to those used in fan-beam aperture-synthesis radio-astronomy10 and medical computer-assisted tomography11, and holds great promise for all-sky imaging with relatively simple (and hence inexpensive) detectors.

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Affiliations

  1. NASA Marshall Space Flight Center, Code ES66, Huntsville, Alabama, 35812, USA

    • S. N. Zhang
    • , G. J. Fishman
    • , B. A. Harmon
    •  & W. S. Paciesas
  2. Universities Space Research Association, Huntsville, Alabama, 35806, USA

    • S. N. Zhang
  3. University of Alabama in Huntsville, Huntsville, Alabama, 35899, USA

    • W. S. Paciesas

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https://doi.org/10.1038/366245a0

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