I guess the point they are trying to make is that 500km (or 300km) is essentially hugging the planet. Which means that, if it is night, they will be in the shad

I guess the point they are trying to make is that 500km (or 300km) is essentially hugging the planet. Which means that, if it is night, they will be in the shadow for the majority of the time. The satellites you can easily see at any time are much higher up.