The launch of NASA’s twin GRAIL spacecraft

The next-to-last Delta 2 rocket is being stacked at its California launch site to take flight in January to put a civilian weather satellite into polar orbit.

The satellite awaiting launch early Saturday from California aboard the final flight of the venerable Delta 2 rocket should allow scientists to more precisely track changes in our planet’s ice sheets, using six green laser beams to chart the height and slope of polar ice and glaciers, providing a key input into climate change research.

NASA’s innovative soil moisture mapper, a new environmental satellite launching in January, has been fueled up for blastoff from Vandenberg Air Force Base in California.