Radiometric Data Analysis of the SSTL Line Imager 4 Band (SLIM4) on the NEO-1 Satellite

Abstract

SSTL Line Imager 4 Band (SLIM4) is one of the payloads on the NEO-1 satellite, developed by the National Research and Innovation Agency (BRIN) in Indonesia. The prelaunch calibration process is required to support the camera’s performance. Prelaunch camera calibration consists of two types: radiometric and geometric calibration. This study focuses on the radiometric calibration process. The radiometric calibration process requires several types of radiometric measurements, including vignetting, dark, parameter variation, and spectral measurements. From these measurements, the camera’s radiometric data are obtained. These data were then processed and analyzed to determine the SLIM4 radiometric characteristics. The results show that, based on the vignetting measurement, the blue channel has a lower Digital Number (DN) compared to the other channels (red, green, and NIR). The dark measurement indicates that SLIM4 still records DN values ranging from 0.4% to 1.2% from DN under illuminated conditions. The parameter variation measurement shows that the relationship between exposure time and DN is directly proportional, the relationship between gain and DN follows an exponential pattern, and the relationship between offset and DN exhibits a fluctuating pattern. Additionally, the spectral measurement provides the actual Full Width at Half Maximum (FWHM) values for each SLIM4 channel. Based on this study, the radiometric calibration coefficients for SLIM4 can be calculated and applied to the system, enabling users to make full use of SLIM4 imagery.