SpaceX has just conducted its 10th launch of 2018, sending satellites for Iridium Communications and NASA into space and reusing part of a previously flown rocket. The Falcon 9 rocket blasted off from Vandenberg Air Force Base in California at around 12:47 p.m. on Tuesday, sending five Iridium NEXT satellites into space to help replace the largest commercial satellite network in the world.

But the mission also involved sending twin satellites for a joint project between NASA and the German Research Centre for Geosciences. The satellites are for the Gravity Recovery and Climate Experiment Follow-On project, which will measure the distribution of the Earth’s mass so it can monitor things like sea level and ice sheets.

The Grace-FO satellites were deployed first, just 11 minutes after launch, while the five Iridium satellites deployed about an hour after liftoff. This time, SpaceX did not try to recover the first stage of the rocket.