The launch of NASA’s twin GRAIL spacecraft

NASA’s ICESat 2 satellite has been bolted atop a United Launch Alliance Delta 2 rocket at Vandenberg Air Force Base in California as ground teams prepare for the final liftoff of the workhorse launcher Sept. 15.

Mars Pathfinder Mission Director Tony Spear narrates a video describing the launch preparations for the Mars Pathfinder spacecraft and the Sojourner rover.

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.