During training, astronauts are familiarized with the engineering systems of the spacecraft including spacecraft propulsion, spacecraft thermal control, and life support systems. In addition to this, astronauts receive training in orbital mechanics, scientific experimentation, earth observation, and astronomy. This training is particularly important for missions when an astronaut will encounter multiple systems (for example on the International Space Station (ISS)). Training is performed in order to prepare astronauts for events that may pose a hazard to their health, the health of the crew, or the successful completion of the mission. These types of events may be: failure of a critical life support system, capsule depressurization, fire, and other life-threatening events. In addition to the need to train for hazardous events, astronauts will also need to train to ensure the successful completion of their mission. This could be in the form of training for EVA, scientific experimentation, or spacecraft piloting.