Complex sentence: Laura's fiancé Allan and fellow astronaut Tony volunteer; they travel on the spaceship "Meteor" to Phobos, one of the two moons of Mars, where they launch the observation satellite.
Split into simpler sentences: Laura's fiancé Allan and fellow astronaut Tony volunteer. They travel on the spaceship "Meteor" to Phobos, one of the two moons of Mars, where they launch the observation satellite.