Scheduled to launch no earlier than May 22, the twin satellites of the Gravity Recovery and Climate Experiment Follow-On (GRACE-FO) mission, a collaboration between NASA and the German Research Centre for Geosciences (GFZ), will continue the work of monitoring changes in the world’s water cycle and surface mass, which was so well performed by the original GRACE mission. There are far more than five things to say about this amazing new-old mission; but here are a few favorite facts.