David Jarrett, GRACE-FO program executive in the Earth Science Division at NASA Headquarters, left, and Phil Morton, NASA GRACE-FO project manager at JPL, discuss the upcoming launch of the Gravity Recovery and Climate Experiment Follow-On (GRACE-FO) mission with Karen Fox of NASA's Office of Communications, Monday, April 30, 2018 at NASA Headquarters in Washington. The twin GRACE-FO spacecraft will measure and monitor monthly changes in how mass is redistributed within and among Earth's atmosphere, oceans, land and ice sheets, as well as within Earth itself. Photo Credit: (NASA/Joel Kowsky)