 The GRACE follow-on satellites will launch on a SpaceX Falcon 9 rocket. GRACE is a gravity mission. It's a mission that measures the gravity of the Earth. The thing that's really important about GRACE is it measures the change in the Earth's gravity from one month to the next and that tells you how mass moves around the Earth and the only thing that really moves around from one month to the next is water and so it can tell us things like changes in sea level rises. It can give us a complete map of the melting of ice in Greenland or Antarctica but it can also tell us how the groundwater changes in the Murray-Darling Basin for example from one month to the next. What GRACE does is it puts up two satellites which are 200 kilometers apart and they're basically following each other around in this orbit and when one of them passes over an area of higher mass concentration it speeds up and then slows down. The satellites are 200 kilometers apart and they move closer together and further apart by about the diameter of a red blood cell. If the groundwater level changes by only a few millimeters that's enough that the spacecraft 500 kilometers away can sense that motion and then we can use that to inform policy makers or farmers who are relying on irrigation about where things are headed and what we need to do to change. So this will be the first mission that shoots laser beams between spacecraft and makes what's called a coherent measurement. This is actually the same technology that the multi-billion dollar gravitational wave detector mission that will launch in a round decade will rely on and there are already plans to do missions not just around Earth but also around Mars and other planets to map the mass and the water in those planets. One of the things I loved about this project is it brought together people from all over it brought together scientists, engineers, physicists, people who studied geology and it brought them from the ANU from CSIRO and even private companies EOS space systems to bring all that expertise together and deliver something which is really world leading.