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​We can see stars at night as they all shine by the light of their own. The moon, the planets and satellites do not generate light but are lit by the sun instead. During the night on Earth, we are standing within the Earth’s own shadow and the sun is below the horizon. Stand on a ladder and you won’t expect to see the sun, walk to the top of a hill, still no sun, fly up in a plane to 4000 metres; nope! Fly up in a rocket to 300 km or so and aha! We see the sun above the horizon again. It’s now illuminating you but the ground down below is in darkness with city street lights, fires and flares from oil rigs.

This is how professionals track satellites...