The Astronomy Book

262

O

n August 20, 1977, the
Voyager 2 spacecraft
was launched from Cape
Canaveral in Florida. Two weeks
later, its sister craft Voyager 1
was launched. Thus began the
most ambitious exploration of the
solar system ever. The launch
was the culmination of more than
a decade’s work. The core mission
would run for 12 years, but an
interstellar mission continues.

Going interplanetary
By the early 1960s, both the Soviet
and US space agencies were sending
missions to other planets. There were

more failures than successes, but

over the decade robotic spacecraft

began sending back close-up images

of Venus and Mars. The NASA craft

were part of the Mariner program,

run largely from the Jet Propulsion

Laboratory (JPL) in California. The

mathematicians at JPL perfected

the art of the “flyby”—sending a

spacecraft on a trajectory that had

it fly past a planet close enough to

photograph and observe it, albeit

too quickly to enter its orbit. In

1965, a graduate student named

Gary Flandro, who was working at

JPL for the summer, was given the

task of figuring out routes to the

EXPLORING THE SOLAR SYSTEM

outer planets and discovered that,

in 1978, all the outer planets would

be on the same side of the sun. His

calculations revealed that this had

not happened since 1801, and would

not occur again until 2153.

Flandro saw the opportunity

for a Grand Tour of the outer solar

system, but the distances involved

were far beyond the capabilities of

the spacecraft of the day. In 1965,

Mars’s alignment made it the

IN CONTEXT

KEY ORGANIZATION

NASA—Voyager mission

(1977–)

BEFORE

1962 Mariner 2 passes Venus

in the first planetary flyby.

1965 Mariner 4 is the first

craft to visit Mars.

1970 Venera 7 makes the

first soft landing on Venus.

1973 Pioneer 10 is the first

spacecraft to cross the asteroid

belt en route to Jupiter.

1976 Viking 1 sends pictures

from the surface of Mars.

AFTER

1995 The Galileo spacecraft

goes into orbit around Jupiter.

1997 Sojourner is the first

rover to land on Mars.

2005 The Cassini orbiter

releases the Huygens probe,

which touches down on Titan.

2015 New Horizons makes the

first flyby of Pluto and Charon.

A Titan 3E rocket lifts off carrying

the Voyager 1 spacecraft as its payload.

The Titan 3E was the most powerful

launch vehicle of its time.