The extravehicular mobility unit is the suit that astronauts wear when they leave the Earth-like atmosphere of the crew compartment and enter into the vacuum of space. In other words, itÕs a space suit. The EMU contains about seven hoursÕ worth of oxygen. Its life support systems control the temperature of the suit and make sure the astronaut doesnÕt get too hot or too cold. It has a communications device (known as a ÒSnoopy CapÓ) that allows the astronaut to communicate with the members in the Orbiter. A television camera on the suit allows the crew inside to see what the astronaut outside is viewing. The suit also has computer instruments that monitor the astronautÕs heart activity.