Engineers dressed in Self-Contained Atmospheric Protective Ensemble, or SCAPE suits, fuel Planck with liquid hydrazine on 15 April 2009.

Planck will use its thrusters, propelled by liquid hydrazine, for manoeuvres once in orbit. This is a volatile and toxic substance, commonly used as rocket fuel. The critical fuelling operations required plenty of preparation, including safety training exercises for the fuelling team, and was executed with great care.