I’m playing a mission, but the robot is off my screen, how do I see him?

You have two options! Firstly, you can walk your unit around, so that you are closer to the robot you wish to fire at. To do this, place your cursor just above the planet/meteor surface where you want your robot to move to and click. Secondly, you can rotate the planet/meteor (which will also zoom out), to do this click and drag on the planet body (i.e. beneath the surface) and you should find the planet/meteor will rotate!