On July 14, 2015, NASA’s New Horizons spacecraft will make history as it carries out the first flyby of Pluto and its moons. This is an exciting, old-school-style reconnaissance mission of exploration straight out of the early Space Age, the likes of which hasn’t been conducted since Voyager 2’s flyby of Neptune in 1989. First flybys are always exciting times of discovery, as these missions give us a close look at mysterious worlds and pave the way for future orbiters, landers and possibly even crewed missions. On the eve of humanity’s exploration of Pluto, here’s a glimpse at other historic flyby missions that gave us our first glimpse of other worlds. (They’re listed in chronological order, from earliest to most recent.)
10. Soviets Reach Far Side of the Moon
After several failed attempts by both the United States and the Soviet Union to send a spacecraft to the Moon, the Russians launched spacecraft Luna 3 on Oct. 4, 1959 — two years to the day after the launch of Sputnik 1 — and achieved another first for the Soviet Union, as it flew past the Moon and beamed back the first blurry images of the lunar far side. This gave humanity its first glimpse of the hidden half of the Moon never visible from the Earth; it’s also the reason lunar far-side features bear such names as the Mare Moscoviense (Sea of Moscow).
9. U.S. Cheers Mariner 2 Mission to Venus
The first successful planetary flyby occurred in mid-December 1962, when Mariner 2 flew past Venus after a journey of more than three months. NASA’s Jet Propulsion Laboratory allowed only 40 pounds of payload for instrumentation, including particle detectors, radiometers … but no camera. Legend has it that engineers told scientists they would simply fly whatever was ready by launch date, whether it was dead-weight ballast or not. Mariner 2 flew within about 22,000 miles of Venus and revealed scorching temperatures and the lack of an appreciable magnetic field surrounding the planet. By the way, a young Carl Sagan worked as one of the researchers on the Mariner 2 mission.
The successful mission sparked celebrations around the U.S. Until that point, the Soviet Union had dominated the Space Race, achieving historic firsts with the launch of Sputnik, sending the first man into space, etc. Mockups of Mariner 2 were in parades and festivals and JPL director William Pickering appeared on the cover of Time magazine.
8. Mariner 4 Beams Back Pictures From Mars
NASA recorded another first in 1965, when Mariner 4 flew past Mars. Coincidentally, this occurred 50 years to the day before the New Horizons encounter with Pluto. Mariner 4 also carried the first video camera aboard a successful interplanetary spacecraft, which beamed back 22 pictures to Earth as the spacecraft passed just over 6,000 miles from the surface of the Red Planet. The imaging team actually hand drew the first Mariner 4 image of Mars as a comparison for proof that the camera was functioning properly, translating data into pixels by hand onto strips of paper for a hasty press release.
7. Pioneer 10 Passes Jupiter on Way to Deep Space
Often forgotten now, Pioneer 10 was the first spacecraft to travel beyond the asteroid belt and explore Jupiter in 1973. The spacecraft passed within about 81,000 miles of Jupiter’s towering cloudtops. Pioneer 10 carried a suite of instruments that included a photopolarimeter, which was used to build the first close-up images of the giant planet. Pioneer 10 was the first spacecraft sent on an escape trajectory out of the solar system, and carries a plaque with diagrams and greetings to any extraterrestrials that may come across her in the next few million years. Through the years, Pioneer 11, Voyagers 1 and 2, Galileo and New Horizons have all visited Jupiter, to be joined by the Juno spacecraft in 2016. On a final note, Pioneer 10 kept transmitting for many years after passing Jupiter. NASA received its last transmission from Pioneer 10 in January 2003 — almost 30 years after its historic flyby of the planet.
6. Mariner 10 Makes First Visit to Mercury
In 1974, NASA’s Mariner 10 became the first spacecraft to fly past the innermost planet, and was the only spacecraft to have visited Mercury until MESSENGER entered orbit around the tiny world in 2011. Mariner 10 was also the first spacecraft to use a gravitational slingshot maneuver as it passed Venus, a technique common today. Mariner 10 conducted three flybys of Mercury from 1974 to 1975 — the closest just 200 miles above the surface — and discovered the planet has a weak magnetic field.
During the mission the probe captured more than 2,500 photos. Just to show you how far NASA has progressed in the realm of photography, MESSENGER returned more than 250,000 images during its mission. Oh, although Mariner 10 made its last transmission to Earth in 1975, 40 years later it is still believed to be orbiting the Sun.
5. Pioneer 11, Voyager 1 Explore Saturn
Pioneer 11 gave us our first close-ups of Saturn in 1979, and also provided our first look at Saturn’s largest moon, Titan. Voyager 1 followed a year later. Since then, Voyager 1 has left the solar system and entered interstellar space; today, it is the most distant human artifact at almost 132 astronomical units (1 AU = the distance from the Earth to the Sun, or 93 million miles) and counting. The Pioneer and Voyager missions took advantage of a rare alignment of the outer planets in the 1970s and ’80s to conduct multiple flyby missions.
4. Voyager 2 Remains Only Spacecraft to Visit Uranus
To date, only one spacecraft has visited Uranus. Voyager 2 passed within 50,600 miles of the Uranian clouds in January 1986. The spacecraft studied Uranus, its moons and its ring system just discovered nine years earlier, and discovered 10 new moons of Uranus for good measure. Both Uranus and Neptune were secondary objectives for Voyager 2 and part of its extended mission.
3. Voyager 2 Uncovers Strange Features on Neptune
NASA checked another planet off its “bucket list” thanks to Voyager 2’s encounter with Neptune in 1989. Voyager 2 passed 3,000 miles above Neptune’s north pole, and discovered a system of planetary rings around the ice giant world, a mysterious feature dubbed “The Great Dark Spot,” and spotted six additional moons. On a pass by Neptune’s large moon Triton, it discovered evidence for ice geysers. Both Voyagers 1 and 2 are still in communication with controllers on Earth, and continue to transmit data.
2. International Mission Makes First Asteroid Flyby
The first asteroid flyby involved a joint effort between the U.S. and Germany in launching the Galileo spacecraft, which visited asteroid 951 Gaspra en route to Jupiter in 1991. Galileo passed roughly 1,000 miles from the 11-mile-long asteroid, snapping color pictures of its pockmarked surface. NASA missions such as NEAR-Shoemaker, Deep Space 1 and Dawn have all since visited asteroids up close, and the OSIRIS-REx sample return mission to an asteroid launches in 2016.
1. New Horizons to Visit Kuiper Belt Objects
Pluto isn’t New Horizons’ only target as it heads out of the solar system. The spacecraft will use what remains of its fuel after its Pluto encounter to maneuver for a possible flyby of a Kuiper Belt Object in 2018 or 2019. Said maneuvering can be only slight, and any potential KBO targets suitable for a flyby must lie along New Horizons’ general flight path. In October 2014 a search team using the Hubble Space Telescope announced the discovery of three possible targets; the best candidate, 2014 MU69, is thought to be 20 to 60 miles in diameter. The final decision for a target is expected to be announced in August 2015.
One More: Solar Probe Makes First Flyby of Comet
Launched in 1978, the International Sun/Earth Explorer 3 was a joint NASA/European Space Agency spacecraft that originally studied the solar environment. But a few years into the mission, controllers rechristened it the International Cometary Explorer (ICE), and it made history when it flew past Comet Giacobini-Zinner in 1985. The spacecraft returned to the neighborhood of the Earth and was actually contacted and rebooted (before being lost once again) by a private effort headed by Skycorp Inc. in 2014.