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Abstract :
[en] As with all optical systems the calibration of wide-field ultraviolet systems includes three main areas: sensitivity, imaging quality, and imaging capability. The one thing that makes these calibrations difficult is the need for working in vacuum substantially extending the required time and effort compared to visible systems. In theory a ray tracing and characterization of each individual component of the optical system (mirrors, windows, grating) should provide the transmission efficiency of the combined system but potential unknown effects (contamination, misalignment, measurement errors) will make the final error too large for most applications. Therefore it is desirable to test and measure the optical properties of the whole system in vacuum and compare the overall response to the response of a calibrated photon detector. Based on the experience with the IMAGE Spectrographic Imager (SI) and Wide-band Imaging Camera (WIC), and the ICON-FUV instrument we will discuss the steps and procedures for the proper radiometric sensitivity and pass-band calibration, spot size, imaging distortions, flat field and field of view determination.
