Radiometric Calibration of In-Orbit LAPAN-A3 Thermal Infrared Imager Using Himawari-8 Satellite AHI Sensor

The LAPAN-A3/IPB satellite has an advanced FLIR thermal infrared (TIR) sensor with impressive technical specifications, 640 × 320 resolution, 8–12 µm wavelength, and −40 to 80 °C temperature range. It captures 92 km-wide images but converting its 14-bit analog video signal to digital images and conducting radiometric calibration is challenging. In this research effort, we do radiometric calibration of TIR LAPAN A3 by utilizing the IR1 channel of the Advanced Himawari Imager (AHI) aboard the Himawari-8 satellite. The calibration process entails a series of essential image and data processing steps. It commences with creating a digital mosaic of TIR data using the Random Sample Consensus (RANSAC) algorithm. Subsequently, this mosaic is adjusted to align with the AHI image, establishing the crucial relationship between the digital number (DN) of TIR LAPAN A3 and the IR1 channel of the AHI Himawari-8 satellite. This established relationship facilitates the conversion of DN values from the TIR sensor into brightness temperature (BT), with the AHI IR1 channel as a reference. However, the validation process encounters particular challenges, particularly in image discontinuities observed during mosaic creation due to the inherent low image quality resulting from the video-to-image conversion process. Nevertheless, despite these challenges, the validation results from two distinct locations (Surabaya and Bengkulu) offer promising insights. The LAPAN-A3/IPB satellite’s TIR sensor can effectively estimate BT, providing consistent results with significant potential for various applications. Future research will focus on enhancing the accuracy and applicability of the TIR sensor’s data through radiometric calibration via in-situ measurements.