 The first two craft used the same spacecraft bus as the Block I Rangers, each weighing and instrumented to perform radiometric temperature measurements of the planet, and to measure interplanetary magnetic fields and particles.Mariner 1's Atlas-Agena malfunctioned and went off course, requiring its destruction approximately 5 minutes after liftoff.Mariner 2 successfully made the 3½-month flight, becoming the first spacecraft to fly by another planet.