The Compton Gamma-Ray Observatory

The CGRO carried four separate, complementary gamma-ray telescopes with overlapping energy ranges. 

The Oriented Scintillation Spectroscopy Experiment (OSSE) was designed to carry out pointed spectral observations of gamma-ray sources in the range from 0.05 to 10 MeV, with capability above 10 MeV for solar gamma-ray and neutron observations. The four OSSE detectors were collimated scintillators (with a 4° x 11° field of view) that were movable over a single axis, allowing a rapid response to targets of opportunity such as solar flares. 

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The Compton Telescope (COMPTEL) on the Compton Gamma Ray Observatory (CGRO) was the first instrument built to detect 7-rays and solar neutrons in space [Ryan et al., 1993a], COMPTEL observations of the June 15, 1991, solar neutron event were the first that allowed to generate an image of the Sun in neutrons [Ryan et al., 1993b Nieminen, 1997],... 

One method in which this division is explicit is maximum entropy (Max-Ent) which has proved to be very effective in producing images from the COMPTEL instrument on the Compton Gamma Ray Observatory CGRO. In this paper I briefly describe MaxEnt and illustrate applications to COMPTEL data for imaging of continuum emission from point sources and for imaging the full sky. Applications to line emission are covered by R. Diehl in an accompanying paper. I also mention some new developments in Bayesian methods. 

The galactic 1.806 MeV emission from COMPTEL on the Compton Gamma Ray Observatory has mapped the distribution of Al within the galactic plane. Although it is possible that the A1 is from a number of point sources it seems more likely that the emission is extended, and has structure on scales of < 4 . 

FIGURE 4 The gamma-ray spectrum of the June 4, 1991, solar flare obtained with the OSSE instrument aboard the Compton Gamma Ray Observatory. Prominent gamma-ray emission lines are identified, along with the primary processes responsible for both the observed line and continuum emission. (Courtesy NASA and the CGRO OSSE Instrument Team (G. H. Share and R. J. Murphy.))... 

FIGURE 11 Time profiles for a sample of gamma-ray bursts (GRBs), obtained with the BATSE instrument aboard the Compton Gamma Ray Observatory. These profiles illustrate the rich diversity in temporal structure, intensities, and durations for gamma-ray bursts, no two of which are exactly alike in all respects. (Courtesy NASA and the CGRO BATSE Instrument Team.)... 

FIGURE 16 Schematic of the Imaging Compton Telescope (COMPTEL) on board the Compton Gamma Ray Observatory illustrating the double-scatter technique employed in Compton telescopes. (Courtesy NASA, the Max Planck Institute, and the CGRO COMPTEL Instrument Team.)... 

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