NASA's Motive Behind Launching Voyager 1 and 2: A Journey Beyond Our Solar System

NASA's decision to launch Voyager 1 and Voyager 2 in 1977 was grounded in a singular premise: to capture an once-in-a-lifetime opportunity to explore the outer planets of our solar system. These spacecraft were meticulously designed to seize the gravity-slingshot boosts from the planets in order to make a Grand Tour of the outer planets.

Historical Context and Mission Objectives

The launch of Voyagers 1 and 2 was not an ordinary mission. While both spacecraft were intended to visit the outer planets, their missions were tailored to specific objectives:

Voyager 1 was specifically aimed at exploring Titan, the largest moon of Saturn. Voyager 2 was tasked with a more extensive Grand Tour, visiting Jupiter, Saturn, Uranus, and Neptune.

This dual approach required separate trajectories, as each spacecraft had to be positioned to take advantage of the planets' gravitational fields for optimal planetary encounters.

Unique Opportunity

The alignment of the outer planets in their orbits provided a unique opportunity that occurs only once every 175 years, making it imperative for NASA to act quickly. The alignment was critical for the success of the Voyager program:

Jupiter, Saturn, Uranus, and Neptune were aligned in a way that allowed a single spacecraft to fly past all four planets, a feat that would otherwise be impossible with the current technology and fuel constraints.

Image credit: University of Colorado Boulder Laboratory for Atmospheric and Space Physics

A Spectacular Success: Expanded Opportunities

The Voyager missions were both spectacular and groundbreaking. While the primary mission targets were the outer planets, these spacecraft continued to function beyond their initial goals. Voyager 2, in particular, played a crucial role by being the only probe to visit Uranus and Neptune. However, the Voyagers' journeys extended well beyond the outer planets, entering interstellar space in 2012 and 2018, respectively.

Interstellar Journey: A Long, Long Voyage

While the Voyagers have been traveling for over 46 years, their average velocity is just a little over 1000 light-seconds per year. This means it would take Voyager 1 about 30,000 years to travel a single light-year, and Voyager 2 would need about 120,000 years to reach our nearest stellar neighbor, Alpha Centauri.

The alignment of the outer planets was crucial for these journeys but will not last forever. According to NASA's forecast, Voyager 1 will drift within 1.6 light-years of AC 79 3888 in about 40,000 years, while Voyager 2 is expected to pass 1.7 light-years from Ross 248 in the same time frame. In about 296,000 years, Voyager 2 will pass 4.3 light-years from Sirius, the brightest star in the sky.

These predictions highlight the unique nature of the Voyager Interstellar Mission, as the spacecraft are destined to wander the Milky Way indefinitely, exploring the interstellar space near our solar system.

Despite the absence of planets or stars, the Voyagers are valuable in studying the radiation environment and interstellar medium beyond the influence of the Sun's magnetic field and the solar wind, contributing significantly to our understanding of these fundamental aspects of space.