how we’re able to see satellites in low earth orbits during the night?

529 views

Shouldn’t the earth block their view of the sun, and stop them from lighting up?

Also I’m aware that the satellites have a much higher vantage point and can see the sun even when it’s dark below them but surely in the middle of the night they’d all be blocked out?

In: Physics

>surely in the middle of the night they’d all be blocked out

You are correct there. Unless the satellite has its own light source (there have been a couple of satellites that had bright LED lights as experiments), they rely on the sun and reflected sunlight to be visible. If you see something in the sky in the middle of the night, it is likely not a satellite.

It depends where you live and what season you are in.

In the summer months, from high latitudes, the Sun is only just below the horizon. This means that the satellites don’t have to be much higher up to be lit up, even though it might be dark on the ground.

I’m from just south of Manchester, England. At local midnight tonight, the Sun will be just 14.5 degrees below the horizon in the north.

This means that any satellite passing directly overhead that is higher than 210km / 130 miles will be lit up all night long at this time of year. But practically every satellite orbits higher than that, otherwise it would re-enter within hours or days. Satellites passing well to the south of us can still pass into the Earth’s shadow though.

If you are further south, then only higher orbiting satellites will be visible at midnight. E.g. if you are in New York, then a midnight passing satellite would have to be higher than 800km / 500 miles to be visible at this time of year. That’s higher than the Starlink satellites currently are (between 400-500km).

In winter it’s a different story. Satellites are only typically visible for a short time after dusk and before dawn.