To make its observations in faint infrared light, the Webb needs to be cooled to just a few tens of degrees above absolute zero. To accomplish this goal, it will dwell in deep space well beyond the orbit of the moon, at one of the so-called "Lagrangian points." At this spot, known as L-2, the gravitational pull of the sun and Earth balance out. That will allow the spacecraft to remain in the same position relative to the Earth and sun with little effort; that's important because Webb needs to keep these bodies on the same side of the spacecraft in order for its sunshield to be effective.

Once Webb blasts off on top of a rocket, the telescope will take three months to reach its orbital parking spot, roughly 1 million miles from Earth.