Power running low
Voyager 2 is running out of power, and NASA engineers have found a way to keep it alive. The spacecraft relies on heat from decaying plutonium to generate electricity. That power source fades a little each year, forcing mission managers to make hard choices.
Earlier this year, engineers decided to turn off one of the probe's science instruments. The move frees up electricity for the heaters that keep the spacecraft working in the cold of deep space. Without the heaters, fuel lines would freeze and the mission would end.
Voyager 2 launched in 1977 and has been flying for nearly 50 years. It flew past Jupiter, Saturn, Uranus and Neptune before leaving the solar system. Today it travels through interstellar space, the region beyond the Sun's influence.
A maneuver with no room for error
The power-saving step required the spacecraft to shut down and restart systems on its own. Because Voyager 2 is more than 20 billion kilometers away, radio signals take more than 19 hours to travel each way. Engineers could not control the maneuver in real time.
They called the procedure the "Big Bang" because a failure would effectively end the mission. After days of silence, Voyager 2 phoned home. The maneuver worked, and the probe is now expected to keep operating for at least another year.
The team celebrated the success but stayed cautious. Spacecraft this old carry no spare parts, and every new procedure carries risk. Engineers said they will watch the probe closely in the coming months.
What comes next
Voyager 1, the twin spacecraft, is in worse shape. It is running even lower on power and may soon have to shut down additional instruments. Engineers are studying similar tricks to stretch its life.
The two probes have traveled farther than any human-made objects in history. They are the only spacecraft exploring interstellar space directly. Every extra year of data is a gift, scientists say, because the missions cannot be replaced.
NASA has already planned the next steps. If Voyager 2 holds up, the mission could reach the 50-year mark in 2027. The data it sends back helps scientists understand the edge of the solar system and the space beyond.