In “The Martian,” the spacecraft that helps rescue Mark Watney is the Hermes.
The Hermes is the Ares III crew’s orbiting interplanetary vessel. After a dust storm forces the crew to evacuate Mars, they believe Watney has died and depart aboard the Hermes for Earth. Once NASA discovers that Watney is alive, the ship becomes central to the rescue plan: its crew agrees to use a gravity-assist trajectory and return to Mars earlier than the next planned surface mission.
Watney eventually travels to the Ares IV landing site and launches in a modified Mars Ascent Vehicle. The Hermes intercepts him in space, and Commander Melissa Lewis reaches him using a maneuvering unit after the crew improvises to slow the ship. A common mix-up is naming Ares IV: that is the later mission and landing site, not the spacecraft that performs the rescue.