NASA Headquarters Public Affairs Officer Steve Cole, left, moderates the Gravity Recovery and Climate Experiment Follow-On (GRACE-FO) mission prelaunch media briefing with David Jarrett, GRACE-FO program executive in the Earth Science Division at NASA Headquarters; Frank Webb, GRACE-FO project scientist at JPL; Frank Flechtner, GRACE-FO project manager for the German Research Centre for Geosciences (GFZ) in Potsdam, Germany; Phil Morton, NASA GRACE-FO project manager at JPL; and Capt. Jennifer Haden, weather officer, 30th Space Wing, Vandenberg Air Force Base, right, Monday, May 21, 2018, at Vandenberg Air Force Base in California. The twin GRACE-FO spacecraft will measure 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/Bill Ingalls)

NASA Headquarters Public Affairs Officer Steve Cole, left, moderates the Gravity Recovery and Climate Experiment Follow-On (GRACE-FO) mission prelaunch media briefing with David Jarrett, GRACE-FO program executive in the Earth Science Division at NASA Headquarters; Frank Webb, GRACE-FO project scientist at JPL; Frank Flechtner, GRACE-FO project manager for the German Research Centre for Geosciences (GFZ) in Potsdam, Germany; Phil Morton, NASA GRACE-FO project manager at JPL; and Capt. Jennifer Haden, weather officer, 30th Space Wing, Vandenberg Air Force Base, right, Monday, May 21, 2018, at Vandenberg Air Force Base in California. The twin GRACE-FO spacecraft will measure 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/Bill Ingalls)

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)

Karen Fox of NASA's Office of Communications, introduces David Jarrett, GRACE-FO program executive in the Earth Science Division at NASA Headquarters and Phil Morton, NASA GRACE-FO project manager at JPL, during a briefing on the upcoming launch of the Gravity Recovery and Climate Experiment Follow-On (GRACE-FO) mission, 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)

David Jarrett, GRACE-FO program executive in the Earth Science Division at NASA Headquarters is seen during a Gravity Recovery and Climate Experiment Follow-On (GRACE-FO) mission prelaunch media briefing, Monday, May 21, 2018, at Vandenberg Air Force Base in California. The twin GRACE-FO spacecraft will measure 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/Bill Ingalls)

David Jarrett, GRACE-FO program executive in the Earth Science Division at NASA Headquarters, discusses the upcoming launch of the Gravity Recovery and Climate Experiment Follow-On (GRACE-FO) mission, 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)

David Jarrett, GRACE-FO program executive in the Earth Science Division at NASA Headquarters, discusses the Gravity Recovery and Climate Experiment Follow-On (GRACE-FO) mission during a prelaunch media briefing, Monday, May 21, 2018, at Vandenberg Air Force Base in California. The twin GRACE-FO spacecraft will measure 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/Bill Ingalls)

Masten Space Systems’ technician making adjustments to NASA’s autonomous landing technologies payload on Masten’s Xodiac rocket.