The Mariner series of spacecraft were interplanetary probes designed to investigate Mars, Venus, and Mercury. The program included a number of firsts, including the first planetary flyby, the first planetary orbiter, and the first gravity assist.
Of the ten vehicles in the Mariner series, seven were successful and the other three were lost. The planned Mariner 11 and 12 vehicles evolved into Voyager 1 and Voyager 2.
Mariner 1 and Mariner 2 - As the first spacecraft to fly by another planet, Mariner 2 was built as a backup to Mariner 1, which failed shortly after launch to Venus. The Mariner 2 spacecraft was launched on August 27, 1962, sending it on a 3½-month flight to Venus.
- Mission: Venus flyby
- Mass: 203 kg (446 lb)
- Sensors: microwave and infrared radiometers, cosmic dust, solar plasma and high-energy radiation, magnetic fields
- Mission: Mars flyby
- Mass: 261 kg (575 lb)
- Sensors: camera with digital tape recorder (about 20 pictures), cosmic dust, solar plasma, trapped radiation, cosmic rays, magnetic fields, radio occultation and celestial mechanics
- Mission: Venus flyby
- Mass: 245 kg (540 lb)
- Sensors: ultraviolet photometer, cosmic dust, solar plasma, trapped radiation, cosmic rays, magnetic fields, radio occultation and celestial mechanics
- Mission: Mars flybys
- Mass 413 kg (908 lb)
- Sensors: wide- and narrow-angle cameras with digital tape recorder, infrared spectrometer and radiometer, ultraviolet spectrometer, radio occultation and celestial mechanics
- Mission: orbit Mars
- Mass 998 kg (2,200 lb)
- Sensors: wide- and narrow-angle cameras with digital tape recorder, infrared spectrometer and radiometer, ultraviolet spectrometer, radio occultation and celestial mechanics
- Mission: Venus and Mercury flybys
- Mass: 433 kg (952 lb)
- Sensors: twin narrow-angle cameras with digital tape recorder, ultraviolet spectrometer, infrared radiometer, solar plasma, charged particles, magnetic fields, radio occultation and celestial mechanics