Number of telescope closures due to satellites

Historical number of engineering target closures due to satellites for Gemini South, one half of the International Gemini Observatory operated by NOIRLab (upper left), Keck 1 (upper right), Keck 2 (lower left), and Lick Observatory (lower right), covering 2012 to early 2023. The number of closures per telescope depends upon a number of variables such as the laser power, the telescope’s location, the size of the ‘keep-out cone’ etc. The vertical axes of these four panels have been normalized to an arbitrary common scale to illustrate the common trend. It can be seen that the number of closure windows began to increase after May 2019 when the first Starlink satellites were launched (red dotted line), followed by a fall-off after the blue dotted line which indicates the US Space Command’s Laser Clearinghouse Waiver for the Starlink satellites.

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