Voyager Spacecraft Sail On, 41 Years After Launch
Nearly 41 years after lifting off, NASA’s historic Voyager mission is still exploring the cosmos.
The twin spacecraft launched several weeks apart in 1977 — Voyager 2 last Aug. 20 and Voyager 1 last Sept. 5 — with an initial goal to explore the outer solar system.
Voyager 1 flew by Jupiter and Saturn, while its twin took advantage of an unusual planetary alignment to visit Jupiter, Saturn, Uranus and Neptune.
And then the spacecraft kept on flying, for billions and billions of miles. Both remain active today, beaming data home from previously unexplored realms.
Indeed, in August 2012, Voyager 1 became the first human-made object ever to reach interstellar space.
The mission’s legacy reached into film, art and music with the inclusion of a “Golden Record” of Earth messages, sounds and pictures designed to give any prospective alien who encountered it an idea of what humanity and our home planet are like.
This time capsule is expected to last billions of years.
The spacecraft are now flying through space far away from any planet or star; their next close encounter with a cosmic object isn’t expected to occur for 40,000 years.
Their observations, however, are giving scientists more insight into where the sun’s influence diminishes in our solar system, and where interstellar space begins.
Voyager 1 is nearly 13 billion miles (21 billion kilometers) from Earth and has spent five years in interstellar space.
This zone is not completely empty; it contains material left over from stars that exploded as supernovas millions of years ago.
The “interstellar medium” (as the space in this region is called) is not a threat to Voyager 1. Rather, it’s an interesting environment that the spacecraft is studying.
Voyager 2 is nearly 11 billion miles (18 billion km) from Earth and will likely enter interstellar space in a few years, NASA officials have said.
Its observations from the edge of the solar system help scientists make comparisons between interstellar space and the heliosphere.
When Voyager 2 crosses the boundary, the two spacecraft can sample the interstellar medium from two different locations at the same time.
Mission designers made the spacecraft robust to make sure they could survive the harsh radiation environment at Jupiter.
This included so-called redundant systems — meaning the spacecraft can switch to backup systems if needed — and power supplies that have lasted well beyond the spacecraft’s primary mission.
Each of the spacecraft is powered by three radioisotope thermoelectric generators, which convert the heat produced by the radioactive decay of plutonium-238 into electricity.
The power available to each Voyager, however, decreases by about 4 watts per year.
This requires engineers to dig into 1970s documentation (or to speak with former Voyager personnel) to operate the spacecraft as its power diminishes.
Even with an eye to efficiency, the last science instrument will have to be shut off around 2030, mission team members have said.
But even after that, the Voyagers will continue their journey (albeit without gathering data), flying at more than 30,000 mph (48,280 km/h) and orbiting the Milky Way every 225 million years.
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