SpaceX's Falcon 9 rocket is set to blast off into space carrying twin satellites that will provide key insights into the Earth's changing climate.
NASA will on Tuesday launch its Gravity Recovery and Climate Experiment Follow-On (GRACE-FO) mission, a major project with the German Research Centre for Geosciences (GFZ) that will track the movement of water on the planet.
The satellites will be jetted into orbit aboard a Falcon 9 as part of a "rideshare" launch with five communications satellites on May 22 after the launch was delayed by two days.
It was previously scheduled to take place on May 19 at 1.04pm Pacific Time (9.04pm BST).
Space enthusiasts will be able to watch the rocket take flight on a livestream here.
The pair of spacecraft will then monitor the Earth's water cycle - measuring the movement of water masses across the planet, and mass changes within the Earth itself.
They will note changes in ice sheets and glaciers, underground water storage and sea level, providing a unique view of the Earth's climate.
In a release, NASA said the mission is planned to fly for a minimum of five years.
SpaceX reusable Falcon 9 rocket blasts off for the 50th time
It will launch from Vandenberg Air Force Base in California along with five Iridium communications satellites.
Live launch coverage will stream the event on NASA Television and the agency's website.
GRACE-FO will continue the task of the previous Earth-observing GRACE mission, which mapped variations in the planet's field of gravity, NASA said.
Falcon 9 is a two-stage rocket designed and manufactured by Elon Musk's SpaceX for the reliable and safe transport of satellites and the Dragon spacecraft into orbit.
The rocket has made 53 trips to space since 2012, delivering satellites to orbit as well as delivering and returning cargo from the space station for NASA.
