NASA's much-anticipated and much-delayed launch of the James Webb Space Telescope is set for Saturday, when it will lift off housed in the nose cone of an Ariane 5 rocket from a launch site in Kourou, French Guiana.
"The James Webb Space Telescope is an Apollo moment for all of NASA, for the entire world, but especially for our science programs worldwide," Thomas Zurbuchen, associate administrator for the NASA Science Mission Directorate, said at a news conference earlier this week. "It's the stuff of dreams."
Liftoff from the Guiana Space Center is now scheduled for Dec. 25 at 7:20 a.m. ET, weather permitting.
Weighing a mere 13,700 pounds, the giant, next-generation telescope, which is named after a former NASA administrator, will take 29 days to reach its destination and complete a complex unfolding procedure. Months of calibration will follow before the telescope can begin taking photos of the early universe.
Click and scroll in the window below to explore how the Webb Space Telescope mission compares to the Hubble Space Telescope to go farther and see further:
The telescope will orbit Earth's second Lagrange point, which is nearly 1 million miles from Earth or four times farther into space than the moon. There, the satellite can be balanced by the gravity of the Earth and sun.
This destination is too far away to be repaired or serviced by astronauts if something goes wrong. Still, NASA believes the risk of failure is low, even with the satellite's hundreds of potential failure points while unfolding. The space telescope has taken over 30 years to develop at a cost of around $10 billion.
Webb will be able to view a larger swath of the infrared spectrum than the Hubble space telescope, launched in 1990, is able to observe.
This difference allows Webb to see older light than Hubble, photograph the first stars created after the Big Bang and see stars hidden behind clouds of space dust and gases.
Webb features many scientific advancements, including a 5-layer sun shield - teach the size of a tennis court yet as thin as a human hair - to ensure the sun's infrared light (or heat) doesn't affect the infrared light being observed from the distant universe.
The delicate operation of observing infrared light from more than 170 billion years ago requires a first-of-its-kind infrared sensor refrigerator, which NASA calls a cryocooler, to be kept extremely cold - like -448 degrees fahrenheit cold, or just 12 degrees above the coldest possible point of matter called "absolute zero." The cold helps the telescope's scientific instruments suppress infrared background "noise," according to NASA.
Webb was previously scheduled to launch Dec. 18 but the "sudden, unplanned release of a clamp band caused a vibration throughout the observatory" and forced it to be pushed back to Dec. 22. Forecast high winds caused NASA to scrap both that one and another on Christmas Eve.