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CGRO Timeline

Published by High Energy Astrophysics Science Archive Research Center | National Aeronautics and Space Administration | Metadata Last Checked: February 14, 2026 | Last Modified: 2026-02-10
The Compton Gamma-Ray Observatory (CGRO) was the second of NASA's Great Observatories. It was launched on April 5, 1991, from Space Shuttle Atlantis. It operated successfully for 9 years, and then was safely de-orbited and re-entered the Earth's atmosphere on June 4, 2000. Compton had four instruments that covered an unprecedented six decades of the electromagnetic spectrum, from 30 keV to 30 GeV. In order of increasing spectral energy coverage, these instruments were the Burst And Transient Source Experiment (BATSE), the Oriented Scintillation Spectrometer Experiment (OSSE), the Imaging Compton Telescope (CompTel), and the Energetic Gamma Ray Experiment Telescope (EGRET). BATSE viewed the full sky, as a transient monitor and is thus not included in this database table of pointed telescope observations. Also, EGRET and CompTel had wide fields of view, about 30 degrees, and, as such, viewed multiple targets per X-axis pointing. OSSE could be slewed (about one axis) independently from the spacecraft, so it typically viewed 2 targets per spacecraft Z-axis orientation, or "viewing period." Viewing periods were typically two weeks long. This database table contains the CGRO observations for Cycles 1 through 9. The Cycle 1 observations for EGRET and COMPTEL were part of the All-Sky Survey with no defined targets. This database table was last updated in November 2001. The information contained therein was provided by the Compton Observatory Science Support Center (COSSC). Galactic coordinates were added to the table by the HEASARC in August 2005. Duplicate entries in the table were removed in June 2019. This is a service provided by NASA HEASARC .

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