Launch of the Compton Gamma-ray Observatory by the space shuttle Atlantis

COMPTEL was the MeV Compton gamma-ray telescope on board of the NASA Compton Gamma-Ray observatory (CGRO). This was the second of NASA’s Great Observatories, with17 tons the heaviest scientific payload ever flown at the time of its launch on April 5, 1991 aboard the space shuttle Atlantis. Compton was re-entered into the Earth’s atmosphere on June 4, 2000.

COMPTEL was an imaging Compton telescope that utilizes the Compton effect and two layers of gamma-ray detectors to reconstruct an image of gamma-ray sources in the energy range 0.75 to 30 MeV. It had a field of view of approximately 1 sterradian, an angular resolution of the order of 1 degree and a spectral resolution of 6-10 %. Gamma rays from active galaxies, radioactive supernova remnants, compact objects, and diffuse gamma rays from the interstellar medium were studied with this instrument.

COMPTEL’s upper layer of detectors were filled with a liquid scintillator which scatters an incoming gamma-ray photon according to the Compton effect. This photon is then absorbed by NaI crystals in the lower detectors. The instrument recorded the time, location, and energy of the events in each layer of detectors, which made it possible to determine the direction and energy of the original gamma-ray photon and reconstruct an image and energy spectrum of the source.

SRON participated in the development/building of COMPTEL and in the calibration and data analysis. The four institutes collaborating in the COMPTEL project were the Max Planck Institute für Extraterrestrische Physik in Germany, the Space Science Center of UNH in the USA, the Astrophysics Division of ESA/ESTEC in the Netherlands, and SRON.


Deployment of CGRO from Atlantis into space
First map of the Milky Way in Al26 emission, as seen by COMPTEL
COMPTEL detection principle