The Mariner program was conducted by the American space agency NASA to explore other planets. Between 1962 and late 1973, NASA's Jet Propulsion Laboratory (JPL) designed and built 10 robotic interplanetary probes named Mariner to explore the inner Solar System – visiting the planets Venus, Mars and Mercury for the first time, and returning to Venus and Mars for additional close observations.
The program included a number of interplanetary firsts, including the first successful planetary flyby, the planetary orbiter, and the first gravity assist maneuver. Of the 10 vehicles in the Mariner series, seven were successful, forming the starting point for many subsequent NASA/JPL space probe programs. The planned Mariner Jupiter-Saturn vehicles were adapted into the Voyager program, while the Viking program orbiters were enlarged versions of the Mariner 9 spacecraft. Later Mariner-based spacecraft include Galileo and Magellan, while the second-generation Mariner Mark II series evolved into the Cassini–Huygens probe.
The total cost of the Mariner program was approximately $554 million.
The Mariner program began in 1960 with a series of JPL mission studies for small-scale, frequent exploration of the nearest planets. They were to take advantage of the soon-to-be-available Atlas launch vehicles as well as the developing capability of JPL's Deep Space Instrumentation Facility (later named the Deep Space Network), a global network of ground stations designed to communicate with spacecraft in deep space. The name of the Mariner program was decided in "May 1960 – at the suggestion of Edgar M. Cortright" to have the "planetary mission probes ... patterned after nautical terms, to convey 'the impression of travel to great distances and remote lands.'" That "decision was the basis for naming Mariner, Ranger, Surveyor, and Viking probes."
Each spacecraft was to carry solar panels that would be pointed toward the Sun and a dish antenna that would be pointed at Earth. Each would also carry a host of scientific instruments. Some of the instruments, such as cameras, would need to be pointed at the target body it was studying. Other instruments were non-directional and studied phenomena such as magnetic fields and charged particles. JPL engineers proposed to make the Mariners "three-axis-stabilized," meaning that unlike other space probes they would not spin.
Each of the Mariner projects was designed to have two spacecraft launched on separate rockets, in case of difficulties with the nearly untried launch vehicles. Mariner 1, Mariner 3, and Mariner 8 were in fact lost during launch, but their backups were successful. No Mariners were lost in later flight to their destination planets or before completing their scientific missions.
All Mariner spacecraft were based on a hexagonal or octagonal bus, which housed all of the electronics, and to which all components were attached, such as antennae, cameras, propulsion, and power sources. Mariner 2 was based on the Ranger Lunar probe. All of the Mariners launched after Mariner 2 had four solar panels for power, except for Mariner 10, which had two. Additionally, all except Mariner 1, Mariner 2 and Mariner 5 had TV cameras.
The first five Mariners were launched on Atlas-Agena rockets, while the last five used the Atlas-Centaur. All Mariner-based probes after Mariner 10 used the Titan IIIE, Titan IV uncrewed rockets or the Space Shuttle with a solid-fueled Inertial Upper Stage and multiple planetary flybys (each of which provided gravity assist acceleration).
The Mariners were all relatively small robotic explorers, each launched on an Atlas rocket with either an Agena or Centaur upper-stage booster, and weighing less than half a ton (without onboard rocket propellant). Each of their missions was completed within a few months to a year or two, though one of them outlived its original mission and continued to send useful scientific data for three years.
Mariner 1 (P-37) and Mariner 2 (P-38) were two deep-space probes making up NASA's Mariner-R project. The primary goal of the project was to develop and launch two spacecraft sequentially to the near vicinity of Venus, receive communications from the spacecraft and to perform radiometric temperature measurements of the planet. A secondary objective was to make interplanetary magnetic field and/or particle measurements on the way to, and in the vicinity of, Venus. Mariner 1 (designated Mariner R-1) was launched on July 22, 1962, but was destroyed approximately 5 minutes after liftoff by the Air Force range safety officer when its malfunctioning Atlas-Agena rocket went off course. Mariner 2 (designated Mariner R-2) was launched on August 27, 1962, sending it on a 3½-month flight to Venus. The mission was a success, and Mariner 2 became the first spacecraft to have flown by another planet.
On the way it measured for the first time the solar wind, a constant stream of charged particles flowing outward from the Sun. It also measured interplanetary dust, which turned out to be more scarce than predicted. In addition, Mariner 2 detected high-energy charged particles coming from the Sun, including several brief solar flares, as well as cosmic rays from outside the Solar System. As it flew by Venus on December 14, 1962, Mariner 2 scanned the planet with infrared and microwave radiometers, revealing that Venus has cool clouds and an extremely hot surface (because the bright, opaque clouds hide the planet's surface, Mariner 2 was not outfitted with a camera).
Sensors: microwave and infrared radiometers, cosmic dust, solar plasma and high-energy radiation, magnetic fields
Mariner 1 – Destroyed shortly after liftoff.
Mariner 2 – Defunct after successful mission, occupies a heliocentric orbit.
Sisterships Mariner 3 and Mariner 4 were Mars flyby missions.
Mariner 3 was launched on November 5, 1964, but the shroud encasing the spacecraft atop its rocket failed to open properly and Mariner 3 did not get to Mars.
Mariner 4, launched on November 28, 1964, was the first successful flyby of the planet Mars and gave the first glimpse of Mars at close range. The spacecraft flew past Mars on July 14, 1965, collecting the first close-up photographs of another planet. The pictures, played back from a small tape recorder over a long period, showed lunar-type impact craters (just beginning to be photographed at close range from the Moon), some of them touched with frost in the chill Martian evening. The Mariner 4 spacecraft, expected to survive something more than the eight months to Mars encounter, actually lasted about three years in solar orbit, continuing long-term studies of the solar wind environment and making coordinated measurements with Mariner 5, a sister ship launched to Venus in 1967.
Sensors: camera with digital tape recorder (about 20 pictures), cosmic dust, solar plasma, trapped radiation, cosmic rays, magnetic fields, radio occultation and celestial mechanics