The James Webb Space Telescope was fuelled inside the payload preparation facility at Europe’s Spaceport in French Guiana ahead of its launch on Ariane 5.

Webb’s thrusters will use this propellant to make critical course-corrections after separation from Ariane 5, to maintain its prescribed orbit about one and a half million kilometers from Earth, and to repoint the observatory and manage its momentum during operations.

Fuelling any satellite is a particularly delicate operation requiring setup of the equipment and connections, fuelling, and then pressurization.