MPL Aims for Keyhole in the Sky

Simply getting the Polar Lander from Earth to Mars is an extraordinary feat of marksmanship. Once it gets there, after a journey of 430 million miles (700 kilometers), it will face an even trickier task: threading a precise path through the Martian atmosphere. To survive its high-speed atmospheric passage, Mars Polar Lander must pass through a kind of keyhole in the sky called the entry corridor.