Автор: Том Гленн

The International Space Station (ISS) transits Mars, as captured from San Diego, CA on September 14, 2020 at 05:15:47PDT (12:15:47UT).

This required being positioned exactly on the line shown in the map in the video, to within less than 100m accuracy on the ground (Calsky reported the path width of the transit as 90m, so 45m on each side of centerline).  This is complicated by the fact that the ISS orbit is inherently unstable in low Earth orbit, which causes the predicted ground path to change by small amounts leading up to the event.  Even at the time of the event, the best prediction is associated with a small amount of error, often on the order of one ISS diameter (~100m), although sometimes larger than this (several hundred meters is not uncommon). At the time of this image, my telescope was sitting directly on the GPS coordinates of the predicted centerline of the transit, but you can see the center of the ISS was ever so slightly below the disk of Mars. However, it was close enough, and part of the solar…