Internal calibration device for the infrared imager of ISO

The imager of the infrared satellite ISO will allow spectral imaging under very low flux conditions in the two to-eighteen-microns range, close to the fundamental limit of the zodiacal background photon noise. To optimize the performance of the imager, we must use an internal calibration device, mainly to track changes in the responsivity of the pixels of the detectors arrays, the limit of detection greatly depending upon the quality of the flat field corrections in certain cases.The first section introduces ISO and its infrared imager and emphasizes the necessity of in-flight calibration. The following chapter presents the specifications for the internal calibration device. The chosen design for the flight model which consists of an infrared emitter and two integrating spheres, is presented in the third chapter. The last part describes the cryogenic bench dedicated to relative photometric tests, the absolute calibration is made in the camera. Endly we present the results obtained with this facility and final tests to achieve the qualification of the device.