NASA is scheduled to deliver a big, shiny present to the astronomy community on Christmas Day.
The space agency, along with its counterparts in Europe and Canada, will launch the James Webb space telescope 25 years after it was first announced.
The new instrument will succeed the Hubble Space Telescope and use state-of-the-art technology to explore strange new worlds.
For many in the science community, this launch has been a long time coming.
Here's everything you need to know about Saturday's launch.
The Webb Telescope, which is named after the NASA director who served during the 1960s space race, is a joint project between NASA, the European Space Agency (ESA) and the Canadian Space Agency (CSA).
The project began in 1996, but the construction and launch were hit with delays, redesigns and other issues.
The telescope weighs half of the Hubble Telescope and specializes in infrared astronomy. It will operate much farther than any other telescope, roughly 1 million miles away from Earth.
NASA said the instrument can "observe exoplanets located in their stars’ habitable zones, the regions where a planet could harbor liquid water on its surface, and can determine if and where signatures of habitability may be present."
The telescope's crew originally planned to launch the instrument on Christmas Eve, but it was postponed one day because of weather conditions.
It will take off in the Ariane 5 rocket from Europe's Spaceport in French Guiana.
The scheduled launch window is between 7:20 a.m. and 7:52 a.m. ET, according to NASA.
Following the launch, the telescope will undergo six months of commissioning in space, which includes "unfolding its mirrors, sunshield and other smaller systems; cooling down; aligning; and calibrating," NASA said.
How to watch
NASA launched a blog that updates readers on the project's progress and will provide up-to-the-minute updates on Christmas.
The space agency will livestream the launch on several platforms, including its website, YouTube page and other social media accounts. The footage will include video from the launch site and the control center in Maryland.
NASA is also inviting fans to sign up to be a free "virtual guest," which includes "information about highlighted mission activities and access to curated mission resources."