Abstract. Image navigation and registration (INR) processing for the Geostationary Lightning Mapper (GLM) assigns geographic coordinates to lightning events using orbit and attitude telemetry and a geometric calibration that matches coastline features from the GLM background scene against a digital map. Required performance is expressed as an optical angle at the aperture of the instrument of 112 μrad (3σ), equivalent to 4 km at the subsatellite point. This is only one-half the linear dimension of the ground footprint of a detector element at the center of the field of view and is challenging to both attain and validate. Our validation approach uses imagery from the Advanced Baseline Imager (ABI) Band 3 (B03), the ABI channel closest to the GLM spectrally, with 1-km pixel resolution at the subsatellite point, as an INR reference. The finer spatial resolution and the high-accuracy INR (<28 μrad, 3σ) of ABI make it well suited for this application. Since both instruments are on the same platform, no parallax correction is required. We measure positions of feature templates extracted from the GLM background scene relative to the ABI reference image to assign spatial coordinates to the center-points of each template. Almost any feature, except clear-sky ocean scenes, can be used for matching, which allows for spatially dense measurement of INR errors in the forward navigation calculation of a GLM pixel. Cloud motion is compensated during the time between the acquisition of the ABI reference image and the GLM background scene, which further improves validation accuracy. We show that GLM on both GOES-16 and -17 spacecraft satisfy their INR requirements. The spatial and temporal density of validation measurements permits examination of smaller systematic errors, including thermally driven alignment offsets, a discontinuity between focal plane hemispheres arising from a readout artifact, the optical distortion of the GLM lens, and a calibration of the telescope focal length.

中文翻译：

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验证地球同步闪电映射器的图像导航和注册

摘要。Geostationary Lightning Mapper (GLM) 的图像导航和配准 (INR) 处理使用轨道和姿态遥测以及几何校准将地理坐标分配给闪电事件，该几何校准将来自 GLM 背景场景的海岸线特征与数字地图相匹配。所需性能表示为仪器孔径处的光学角度为 112 μrad (3σ)，相当于卫星点处的 4 km。这只是位于视场中心的探测器元件地面足迹线性尺寸的二分之一，并且难以实现和验证。我们的验证方法使用来自高级基线成像仪 (ABI) 波段 3 (B03) 的图像，该 ABI 通道在光谱上最接近 GLM，在卫星点具有 1 公里的像素分辨率，作为 INR 参考。ABI 更精细的空间分辨率和高精度 INR (<28 μrad, 3σ) 使其非常适合此应用。由于两台仪器在同一平台上，因此无需进行视差校正。我们测量从 GLM 背景场景中提取的特征模板相对于 ABI 参考图像的位置，以将空间坐标分配给每个模板的中心点。除了晴空海洋场景外，几乎任何特征都可以用于匹配，这允许在 GLM 像素的前向导航计算中对 INR 误差进行空间密集测量。在获取 ABI 参考图像和 GLM 背景场景之间的时间内补偿云运动，这进一步提高了验证精度。我们表明 GOES-16 和 -17 航天器上的 GLM 都满足其 INR 要求。