Question: what is a space instrument

Helen O'Brien answered on 13 Mar 2018:

The simple answer: a space instrument is an instrument which goes into space! Engineers design instruments to measure properties of space as the satellite travels through it and telescopes to remotely learn more about other bodies (our star and planets) in solar system. I build magnetometers – which measure the magnetic field at the location of the spacecraft. Space is a vacuum, which means it is pretty much empty. But it is not completely empty. The whole of our solar system actually exists is the extended atmosphere of the sun. And this atmosphere, called the solar wind varies depending on how the sun varies. The sun has different moods, some days it is calm and some days it is explosive, and magnetic field tells us about the solar wind.
Instruments built for space have to be low mass and power, very accurate, able to survive the intense vibration of launch, able to survive in a vacuum, able to deal with a lot of thermal cycling (going from hot to cold and back again) and finally able to deal with the harsh radiation environment of space.