The Sustainable Development Science Satellite (SDGSAT-1) was successfully launched on November 5, 2021. It is the world’s first scientific satellite dedicated to serving the United Nations 2030 Agenda for Sustainable Development. To evaluate the on-orbit image quality of its thermal infrared spectrometer (TIS), we propose an improved edge slope (ES) calculation method. Learning from past academic research, we found that the traditional ES calculation methods are limited by various factors. For example, it demands highly on geographical aspects and surface temperature uniformity. In this letter, we interpolate the narrow sea–land boundary region. The edge signal-to-noise ratio and the dip angle are calculated by the selected region to determine whether it satisfies the conditions of ES calculation. The Otsu algorithm is used to find the optimal threshold for the sea–land division, and the subpixel edge positions are extracted by combining with the canny operator. In order to achieve higher precision, we use the modified Fermi function to fit the extracted edge spread function (ESF). During the on-orbit testing of the SDGSAT-1/TIS, we performed ES calculations for a large number of test areas with a flight direction of 0.5 and a scan direction of 0.45.

中文翻译：

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SDGSAT-1热红外光谱仪在轨空间质量评价

可持续发展科学卫星（SDGSAT-1）于2021年11月5日成功发射，是世界上第一颗致力于服务联合国2030年可持续发展议程的科学卫星。为了评估其热红外光谱仪（TIS）的在轨图像质量，我们提出了一种改进的边缘斜率（ES）计算方法。借鉴以往的学术研究，我们发现传统的 ES 计算方法受到各种因素的限制。例如，它对地理方面和地表温度均匀性要求很高。在这封信中，我们插入了狭窄的海陆边界区域。通过所选区域计算边缘信噪比和倾角，以确定是否满足ES计算条件。采用Otsu算法寻找海陆划分的最优阈值，结合canny算子提取亚像素边缘位置。为了达到更高的精度，我们使用修正的费米函数来拟合提取的边缘扩散函数（ESF）。SDGSAT-1/TIS在轨测试期间，我们对飞行方向为0.5、扫描方向为0.45的大量测试区域进行了ES计算。