From: JPL/ NASA Timeline: Chronicles of Discovery
January 31, 1958: Built in just three months, Explorer 1 is launched as the first U.S. satellite; it discovers the Van Allen radiation belts.
March 3, 1959: Pioneer 4 launches and escapes Earth’s gravity to orbit the Sun.
August 27, 1962: Mariner 2 launches and conducts the first flyby of another planet when it visits Venus on December 14.
July 28, 1964: Ranger 7 launches and executes an intentional crash-landing into the Moon on July 31. As it closes in, it sends back more than 4,000 pictures of the lunar surface.
November 28, 1964: Mariner 4 launches with a destination of Mars.
February 17, 1965: Ranger 8 launches and impacts the Moon in Mare Tranquillitatis three days later. This location will become the landing spot for the Apollo 11 astronauts 4-1/2 years later.
March 21, 1965: Ranger 9 launches and three days later impacts the Moon in the 108-kilometer-diameter (67-mile) crater Alphonsus, sending back more than 5,800 images.
July 14, 1965: After an eight-month voyage to Mars, Mariner 4 makes the first flyby of the red planet. The spacecraft radios back the first close-up photos of another planet.
May 30, 1966: Surveyor 1 launches. On June 2, it becomes the first U.S. spacecraft to make a soft landing on the moon.
April 17, 1967: Surveyor 3 launches, lading on the Moon on April 20. Two and a half years later, the Apollo 12 astronauts will land nearby and photograph the Surveyor 3 site.
June 14, 1967: Mariner 5 launches and flies by Venus on October 19.
September 8, 1967: Surveyor 5 launches and lands on the Moon September 11.
November 7, 1967: Surveyor 6 launches and soft-lands on November 10. The lunar mission runs until December 14.
January 7, 1968: Surveyor 7, the last of the Surveyor series, launches and soft-lands on the Moon on November 9. Overall, the Surveyors acquire 90,000 images from five sites on the Moon.
February 24, 1969: Mariner 6 launches. A month later, on March 27, Mariner 7 launches. They complete the first dual mission to Mars with flybys on July 3 and August 5.
May 30, 1971: Mariner 9 launches and reaches Mars on November 13, becoming the first spacecraft to orbit another planet. The craft operates for nearly a year around Mars.
November 3, 1973: Mariner 10 launches on a mission to Mercury and Venus, the first craft designed to visit two planets.
February 5, 1974: Using gravity-assist for the first time, Mariner 10 swings by Venus to borrow the planet’s gravity to propel it on to Mercury, which it passes on March 29. On September 21, it flies past Mercury again.
March 16, 1975: Mariner 19 flies by Mercury a third time.
August 20, 1975: Viking 1 launches an orbiter and lander toward Mars. On September 9, Viking 2 launches a similar orbiter- lander pair.
June 19, 1976: Viking 1 arrives in orbit at Mars. On July 20, its lander becomes the first craft to soft-land on another planet. On August 7, Viking 2 arrives in orbit, and its lander touches down on September 3.
August 20, 1977: Voyager 2 launches, followed by the launch of Voyager 1 on September 5.
June 26, 1978: The experimental Seasat satellite launches to test four instruments that use radar to study Earth and its seas. The satellite collected more ocean topography data than the previous 100 years of shipboard research.
March 5, 1979: Voyager 1 makes its closest approach to Jupiter. On July 9, Voyager 2 flies by the giant planet. Together, the Voyagers take more than 22,000 images of Jupiter and its moons.
November 12, 1980: Voyager 1 flies by Saturn.
August 25, 1981: Voyager 3 flies by Saturn.
October 6, 1981: The Solar Mesosphere Explorer launches to study processes that create and destroy ozone in Earth’s upper atmosphere.
November 12, 1981: The first in a series of radar imagers is launched on the space shuttle.
January 25, 1983: The Infrared Astronomical Satellite launches into Earth orbit. The telescope discovers solid material around distant stars, strongly suggesting the existence of planets.
October 5, 1984: The second in a series of imaging radar missions launches on the space shuttle.
January 24, 1986: Traveling to a planet more distant than any visited before, Voyager 2 makes the first ever flyby of Uranus, nearly 3 billion kilometers (1.8 billion miles) from Earth. Voyager images 15 of Uranus’ moons.
May 4, 1989: Magellan launches a mission to Venus.
August 25, 1989: Voyager 2 is the first spacecraft to fly by Neptune.
October 18, 1989: Galileo launches on a six-year journey to Jupiter.