Live coverage: Two satellites lift off aboard Ariane 5

A new satellite to monitor crops, pollution and the growth of cities blasted off Monday from a tropical spaceport in French Guiana, adding another piece to Europe’s multibillion-dollar fleet of spacecraft tasked to track Earth’s ever-changing environment.

After criss-crossing Europe for a decade, the LISA Pathfinder satellite testbed has reached its last stop before launch in early December on a mission to demonstrate the delicate technologies required to detect elusive low-frequency gravitational waves rippling through the cosmos.

The 13th and 14th operational members of Europe’s Galileo navigation satellite network are set for liftoff Tuesday aboard a Soyuz rocket from French Guiana. Track the progress of the flight with this timeline of key events.