Why do we sterilise satellites?



I understand why we keep deep space probes clean, so as not to contaminate extraterrestrial objects with our super-tough beings.
Why do we do the same with satellites though? It’s not like some aliens are going to get space flu from it, is it?

In: Engineering

Regular satellites that go up into earth orbit are not really fully sterilized. But they are constructed in cleanrooms to prevent wayward particles from ending up inside the spacecraft and possibly causing issues later. Imagine a random hair ending up in a high voltage circuit and then when the satellite is powered up, that hair catches fire and causes other issues. Or think of the issues that would happen if a solar panel couldn’t extend because the track it is mounted to is covered in grease and dirt from the workers hands.

We don’t sterilize satellites to kill of microbes, you’re right there is no contamination risk

We do build them in clean rooms though because they’re going to a place where no one can do maintenance on them (this is changing but still mostly true). If you’re spending a few hundred million on a communication satellite that you’re planning on having last for 10 years, then you want to make sure you take the precautions against some dust or grime taking out a critical system just a few years into operation.

A bit of dust that gets into the bearings of the gyro assembly can wear out a critical part and turn your expensive investment into worthless spacejunk