Webb's launch date is set for December 22, 2021 07:20 EST.
The James Webb Space Telescope will be launched on an Ariane 5 rocket. The launch vehicle is part of the European contribution to the mission. The Ariane 5 is one of the world's most reliable launch vehicles capable of delivering Webb to its destination in space. The European Space Agency (ESA) has agreed to provide an Ariane 5 launcher and associated launch services to NASA for Webb.
The telescope will be able to see just about anything in the sky. However, it has one overriding objective - to see the light coming from the very first stars to shine in the Universe.
These pioneer stars are thought to have switched on about 100-200 million years after the Big Bang, or a little over 13.5 billion years ago.
Webb will be picking out groupings of these stars. They are so far away, their light - even though it moves at 300,000km (186,000 miles) per second - will have taken billions of years to travel the cosmos.
It should be possible for Webb to see (or least detect a faint glow from) the moment when the darkness ended and those first stars flickered into life.
Countdown resumes for December 22 launch
UPDATE NOVEMBER 24, 2021. NASA said today that engineering teams have completed additional testing confirming the James Webb Space Telescope is ready for flight. And that means launch preparations are resuming. The Webb's target launch date is now, officially, December 22 at 7:20 a.m. EST (00:20 UTC; translate UTC to your time). NASA said in a statement:
Additional testing was conducted this week to ensure the observatory's health following an incident that occurred when the release of a clamp band caused a vibration throughout the observatory.
On Wednesday, November 24, engineering teams completed these tests, and a NASA-led anomaly review board concluded no observatory components were damaged in the incident. A "consent to fuel" review was held. And NASA gave approval to begin fueling the observatory. Fueling operations will begin Thursday, November 25, and will take about 10 days.