A sounding rocket is a rocket that ascends into the high atmosphere in order to take all sorts of measurements so we can learn more about the upper atmosphere. They don't go into orbit, so they can be smaller than what we normally think of space rockets. However, they can still go above 100km fairly easily, and they still go very fast.
What I want to know is, how can it accurately measure the ambient temperature at whatever altitude it's at? The rocket will be flying very fast, incurring a lot of heat from air friction.