Observing gamma rays is a difficult task. The gamma-ray photons from distant objects are rare and with their penetrating power they cannot be focused by conventional mirrors or lenses. It requires specially designed detectors to register the gamma rays from space and determine their position of origin on the sky.
INTEGRAL has two such detectors on board: an Imager and a Spectrometer. Two monitor instruments support these instruments: an X-ray monitor and an optical camera. All four instruments are co-aligned and observe the same region of the sky simultaneously. This allows scientists to clearly identify gamma-ray sources, a key feature in studying high-energy processes in the violent Universe.
All instruments are provided by large collaborations encompassing many scientific institutes in the ESA member states, United States, Russia, Czech Republic, and Poland. Principal investigators in different European countries lead the nationally funded collaborations.