Direct Illumination LED Calibration for Type Ia Supernovae Photometry

A calibration method for type Ia supernovae photometry, based on the direct illumination of a telescope with a calibrated light source regrouping multiple LEDs, is proposed. Its purpose is to calibrate the instrument response independently of the atmospheric transmission. The main emphasis of the proposed method is the traceability of the calibration process and a continuous monitoring of the instrument in order to maintain a 0.2% accuracy over years period. Its specificity is to map finely the response of the telescope and its camera as a function all five light ray parameters. This feature is essential to implement a full computer model of the instrument representing the variation of the overall light collection efficiency of each pixel for various filter configurations. We report on hardware developments done for SNDICE, the first application of this direct illumination calibration system to be installed in Canada France Hawai telescope (CFHT) for its leading supernova experiment (SNLS).