Imaging performance of wide-field X-ray Transient Localization Experiment onboard microsatellite KOYOH

We designed a flight model of the wide field X-ray imager on board the microsat KOYOH, referred to as T-LEX, and investigated its imaging performance through laboratory beam tests. T-LEX employs the coded mask method, wherein the aperture pattern of the mask was selected and fabricated from 50,000 patterns using a Monte Carlo approach. Utilizing the obtained mask along with a silicon strip detector, we examined the angular response by varying the incident angle with a stage during X-ray irradiation. The resulting angular response exhibited deviations from the design values, yet it confirmed that the targeted position accuracy of 15 arcminutes is maintained across a range from -20deg to +20deg with the best fit calibrated model.