The following will briefly describe the main telescopes and instruments used to obtain the images presented in the atlas or those used in observations discussed in the text. Detectors are not described. Since there exists significant overlap between telescopes used for submillimeter and radio observations these are considered together.
A1 Gamma ray
kT > 500 keV
The Compton Gamma Ray Observatory (CGRO; Figure A.1) was launched into Earth orbit at 450 km altitude on April 5th, 1991 and re-entered on June 4th, 2000. CGRO contained instruments that could detect radiation with energies from 15 keV to 30 GeV and it was the second of NASA's “Great Observatories”.
These instruments included the Energetic Gamma Ray Experiment Telescope (EGRET) that detected events between 20 MeV and 30 GeV with a positional accuracy of ∼1°. The Imaging Compton Telescope (COMPTEL) covered 1–30 MeV with a positional accuracy of ∼2°. Currently, gamma-ray imaging observations of nearby galaxies are restricted due to a small number of recorded events at poor positional accuracy.
The Fermi Gamma Ray Space Telescope (hereafter Fermi), formerly called the Gamma Ray Large Area Space Telescope or GLAST, was launched on June 11th, 2008 into a 560 km altitude orbit. It is detecting radiation between 8 keV and 300 GeV using the primary instrument, the Large Area Telescope (LAT), and the complementary GLAST Burst Monitor (GBM). The LAT has a large field of view, over 2 steradians (one-fifth of the entire sky), can measure the locations of bright sources to within 1 arcminute and is sensitive to photons from 30 MeV to greater than 300 GeV.