The Mars Reconnaissance Orbiter (MRO) spacecraft has been in orbit around Mars since March 2006. The Context Camera (CTX) on MRO has returned over 115,000 images of the planet at approximately 5–6 meters per pixel, providing nearly global coverage. During that time, Mars has gone through nearly 7 of its own years, changing solar distance from 1.38 to 1.67 AU and the corresponding solar flux by 45% due to its orbital eccentricity. Seasonal effects and transient phenomena affect atmospheric transparency. These changes, along with an aging detector, prevent easily equalizing images to create a visually smoothly illuminated product from CTX images. We have developed a method, based on previous work by other researchers for other datasets, to mitigate almost all brightness variations between images in order to create the appearance of an evenly illuminated, practically seamless mosaic. We describe how the process works, which uses a reference source to tie brightness values, and demonstrate its effects across Mars’ surface. While the workflow developed for this product is applicable to other planetary bodies, it requires a reference source, which may not yet exist.

中文翻译：

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火星上下文相机图像的经验亮度控制和均衡

自2006年3月以来，火星侦察轨道器（MRO）航天器一直在火星上运行。MRO上的背景摄像机（CTX）已以大约每像素5-6米的速度返回了115,000幅行星图像，几乎覆盖了全球。在此期间，火星经历了将近7年的时间，由于其轨道偏心率，使太阳距离从1.38 AU更改为1.67 AU，相应的太阳通量更改了45％。季节效应和短暂现象会影响大气透明度。这些变化以及老化检测器可防止轻松均衡图像以从CTX图像创建视觉上平滑照亮的产品。根据其他研究人员对其他数据集的先前工作，我们已经开发出一种方法来减轻图像之间几乎所有的亮度变化，从而创建均匀照明的外观，实际上是无缝的马赛克。我们将描述该过程的工作原理，该过程使用参考源绑定亮度值，并演示其在火星表面的影响。虽然为该产品开发的工作流程适用于其他行星体，但它需要参考源，但可能不存在。