SpaceX Sends Up Seven Satellites in Tenth Launch of 2018

The new GRACE-FO satellites are replacing a previous pair of satellites that dutifully monitored global changes for over 15 years. Those older GRACE satellites were responsible for discovering Greenland was using 281 billion tons of ice yearly. 

[see-also]

"GRACE was really a revolutionary mission for us understanding the water cycle and how the climate behaves and the trends that are taking place," said Frank Webb, GRACE-FO project scientist at NASA's Jet Propulsion Laboratory.

"This was a view we didn't have before of water on the Earth. We were able to see how water has moved from different parts of the Earth by actually measuring its mass. ... We were able to detect things like loss of ice mass from glaciers, ice sheets, Greenland, places like that, we were able to see storage of water on land where there were floods or depletion of water on land where there are large aquifers and we've been pumping water out."

GRACE satellites (including these two new satellites) fly in uniform pairs so that scientists can have a better read on how much mass is below the flight path. This allows them to calculate water presence and making updated global maps over the flight path every 30 days. These measurements do more for immediate and precise tracking than most other global climate change data. 

"If mass changes on the ground, like in aquifers or melting glaciers or in the oceans and so on, we see it immediately in a range change, which we measure very, very precisely by a microwave tracking system with a precision of about one micrometer," said Frank Flechtner, GRACE-FO project manager at the German Research Centre for Geosciences, or GFZ.

"That's about a tenth (of the width of) a human hair over the distance between Los Angeles and San Diego."

The GRACE-FO satellites are also joined by five Iridium satellites on the Falcon 9. Those satellites are expected to boost communications range of the 50 other satellites already in orbit. This launch makes the Iridium NEXT satellite constellation a conglomeration of 75 satellites (nine of which are spares).