Why do images of earth from space not contain satellites and other space junk?
In: Earth Science
I am one of those newspace satellite engineers, specializing in developing the EO payloads.
The distance argument is the strongest one, but there is also the factor of light. The lighting conditions have to be just perfect, angle of sunlight, the shape and surface on the debris and camera position. The smaller size does not actually matter when there is perfect reflection as that would still fill the pixel up. Think taking a long exposure of the sky, the star is smaller than a pixel but still can be seen in the image. This is true as the background is the void of space, not the case when looking at Earth. It can still happen that the background is well lit and the debris is seen as a dark spot.
A 10cm debris at 300km being imaged at 400km orbit from a satellite that is doing 30cm resolution on earth would surely see it. But most often it would happen over sea or such where the earth image is not of use. Besides, most satellites do 20m – 1000m resolutions, the sub-meter things are very few, and they will have more problems when there are 60000 new satellites up there. But lighting conditions are still important to actually affect the data meaningfully. The problem is much worse for telescopes on ground as they have really high resolution and smallest of the debris can light up with even a fraction of the light. There is a [study](https://astronomy.com/news/2021/04/satellite-skyglow-may-mean-light-pollution-is-unavoidable) that says, they would eventually even reflect man-made light going off earth.
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