SpaceX’s Falcon 9 rocket exploded upon landing Sunday after returning from a trip in which it successfully delivered a satellite to space.

The rocket’s launch occurred without issue and it was able to deliver the Jason-3 science satellite to low-Earth orbit in a mission supporting NASA, the NOAA, the French space agency Centre National d’Etudes Spatiales (CNES), and the European Organisation for the Exploitation of Meteorological Satellites (EUMETSAT). SpaceX CEO Elon Musk wrote on his Twitter account that the touchdown speed was fine, and the problem was that a lockout collet didn’t latch upon the landing, causing the rocket to topple over and explode once its side struck the drone ship.

He later added on Instagram that the issue could have been caused by ice that built up at liftoff.

Musk expects a number of rapid unscheduled disassembly (RUD) incidents will occur this year, but he is optimistic that the rate of those incidents occurring will improve. He also said that he is optimistic about what should occur during the company’s next ship landing.