Voyages of Exploration and Discovery

Voyages of Exploration and Discovery

Launched on August 20, 1977, Voyager 2 moved on an arcing trajectory past the orbit of Mars, through the asteroid belt, to approach the Jupiter system and thread its way past the planet and among its fourteen or so moons.

Jupiter is surrounded by a shell of invisible but extremely dangerous high-energy charged particles. The spacecraft must pass through the outer edge of this radiation belt to examine Jupiter and its moons close up, and to continue its mission to Saturn and beyond.

However, the charged particles can damage the delicate instruments and fry the electronics. Besides, Jupiter is also surrounded by a ring of solid debris, discovered by Voyager I, which Voyager 2 had to traverse. A collision with a small boulder could have sent the spacecraft tumbling widely out of control, its antenna unable to lock on the Earth and its data lost forever.

Voyage to Earth. These voyages of exploration and discovery are the latest in a long series that have characterized and distinguished human history. Carl Sagan, Cosmos Image : © Megan Jorgensen (Elena)

Just before encounter, the mission controllers were restive. There were some alarms and emergencies, but the combined intelligence of the humans on Earth and the robot in space circumvented disaster.

Voyager’s passage by Jupiter accelerated it toward a close encounter with Saturn. Saturn’s gravity has propelled it on to Uranus. After Uranus it plunged on past Neptune, leaving the sloar system, becoming an interstellar spacecraft, fated to roam forever the great ocean between the stars.

Voyager relies on a small nuclear power plant, drawing hundreds of watts from the radioactive decay of a pellet of plutonium. Its three integrated computers and most of its housekeeping functions – for example, its temperature-control system – are localized in its middle. It receives commands from Earth and radios its findings back to Earth through a large antenna, 3.7 meters in diameter.

There are many scientific instruments – ultraviolet and infrared spectrometers, devices to measure charged particles and magnetic fields and the radio emission from Jupiter – but the most productive have been the two television cameras, designed to take tens of thousands of pictures of the planetary islands in the outer solar system.

Most of the scientific instruments of Voyager are on a scan platform, which tracks Jupiter or one of its moons as the spacecraft hurtles past.