Like kids dreaming of presents under the tree, the scientists at the Jupiter control room at the Guiana Space Centre in Kourou are patiently waiting for December 25.

The James Webb Space Telescope—soon to become the most powerful ever to be launched into space—after technical and weather delays is set to take off on Christmas Day from the base in France's South American department.

"We can't wait for it to launch," says Jean-Luc Mestre, engineer and vice-director of operations at the French National Centre for Space Studies (CNES).

This rocket's payload, the Webb telescope, is a piece of technology worked on by thousands of people for over a quarter of a century.

"Everything is ready," Mestre adds. "Now all we need is the right weather."

For days heavy winds and rain have lashed the dense tropical forest surrounding the base, though you'd never know it from inside the vault-like control room, its windowless walls dominated by a bank of glowing screens.

A 1:18 scale model of Juice, ESA's spacecraft to explore the Jupiter system, is being employed to test its radar antenna.

The working version of the RIME instrument (Radar for Icy Moons Exploration), incorporating a 16-m long version of the straight 'dipole' boom seen here under the model spacecraft, will probe up to 9 km deep under the surfaces of the gas giant's main "Galilean' moons.

The testing took place in ESA's Hertz (Hybrid European RF and Antenna Test Zone) chamber based at ESA's ESTEC technical heart in the Netherlands.

Metal walls screen outside radio signals, while spiky foam interior cladding absorbs radio signals internally to create conditions simulating the infinite void of space.

This chamber's hybrid nature makes it unique: Hertz can assess radio signals from antennas either on a local 'near-field' basis or as if the signal has crossed thousands of kilometers of space, allowing it to serve all kinds of satellites and antenna systems.

A scaled model of the #JUICE Radar antenna is under characterization test @TestCentre.