Goals: Voyager 1 and 2 were designed to take advantage of a rare planetary alignment to explore the outer solar system. Voyager 1 targeted Jupiter and Saturn before continuing on to chart the far edges of our solar system.

Accomplishments: Sometime before the year 2020, Voyager 1 will become the first spacecraft to cross the heliopause-the outer boundary of the vast region of space dominated by the solar wind and the sun's magnetic field-and reach interstellar space. In that sense, it can be said that the spacecraft will be able to sample what space is like beyond our solar system. (If we define the solar system as the sun and everything that primarily orbits the sun, however, Voyager 1 will remain within the confines of the solar system until it emerges from the Oort cloud in another 14,000 to 28,000 years).

Voyager 1 has not yet arrived in interstellar space. As the spacecraft's power supply dwindles, it will need to begin shutting down its instruments in 2020. Sometime in 2025 or after, there will be insufficient electricity to power even one instrument, and Voyager 1 will continue its eternal journey among the stars in silence.