Radiometric Calibration of in-orbit LAPAN A3 Thermal Infrared Imager using Himawari-8 satellite AHI Sensor
Halimurrahmana, Romy Hartonob, Kamirulb, Wakhid Abdurrohmanb, Patria Rachman Hakimb, Asif Awaludina,*, Agus Herawanb, Satriya Utamab, Didi Satiadia, Wahyudi Hasbib

aResearch Center for Climate and Atmosphere, National Research and Innovation Agency, Bandung Indonesia
bResearch Center for Satellite Technology, National Research and Innovation Agency, Bogor Indonesia
*corresponding author, email : sf.wldn[at]gmail.com

Abstract

The National Institute of Aeronautics and Space, now integrated into the National Research and Innovation Agency, had launched the LAPAN-A3/IPB satellite equipped with a thermal infrared (TIR) sensor. The thermal imager is provided by FLIR with a resolution of 640x320 using a 60 mm lens and can perform a swath width of around 92km. The output of this thermal camera is a 14-bit analog video. Since the 8-12 &#956-m band sensor is an analog camera, it must be converted into digital images and calibrated to produce brightness temperature (BT). In this research, the radiometric calibration is conducted using the IR1 channel of the Advanced Himawari Imager (AHI) of the Himawari-8 satellite. The TIR sensor resolution is higher than the AHI sensor, thanks to its lower orbit height. The calibration procedure follows several steps of image and data processing. The first is creating a digital image mosaic of TIR data using the Random Sample Consensus (RANSAC) algorithm. The created mosaic image must then be inverted to resemble AHI image. Then, find the relation between the digital number (DN) of the TIR camera and the IR1 channel of Himawari-8. Third, convert the DN of the TIR sensor into BT using the AHI IR1 channel as a reference. Lastly, validate the obtained BT using three overlapped and collocated scenes of both satellite images. According to the results, the RANSAC algorithm recognizes several discontinued images during mosaic creation due to low image quality yielded from video-to-image conversion. However, the validation results from the three locations indicate that the TIR sensor can estimate BT and produce largely consistent results. Further, these results will be followed by radiometric calibration by in-situ measurement.

Keywords: LAPAN A3/IPB, Radiometric Calibration, Thermal Infrared Camera, Temperature

Topic: Atmospheric Sciences