Calibration of the Thermal Infrared Imager TIRI onboard Hera

Thermal Infrared Imager TIRI onboard Hera is now being developed for the investigation of the binary asteroid Didymos and Dimorphos in the European Space Agency Hera mission. This instrument uses a heritage from the Thermal Infrared Imager TIR on Hayabusa2, which observed the C-type asteroid 162173 Ryugu. In the Hera mission, its updated version of instrument is based on Lynred PICO 1024 Gen2 bolometer array (1024 x 768 effective pixels) with almost 4 times higher spatial resolution than TIR. The wavelength range shows 8-14　µm for the thermal average images, as well as 7.8, 8.6, 9.6, 10.6, 13.0 deg for multi-bands). Its FOV covers 13.3 x 10.0 deg with the spatial resolution of 0.013 deg/pixel.

TIRI is now in the test process to check its full functions and performances as well. The calibration for TIRI is to check its focus, to conduct radiometric and geometrical corrections, identification of materials (like terrestrial rocks and meteorites). A set of apparatus were prepared by the TIRI PI team using the collimator (Aperture: 200mm dia., temperature range of -20 to 150℃, Focal position is 60 deg or higher), the flat cavity blackbody ( 175 x 175　mm, -20 to 125 ℃ for fact change of temperature), and a cold plate plus the cryocooler for the target sample (room temperature to -123 deg). There are some rocks and meteorites to be set as the multiband test samples at the target material, With these information and the presentation, details of the TIRI preparation and development are shown. The test results for TIRI will be presented with some data set and physical properties using the sample.