The US space agency lost contact with the Voyager 2 probe after a series of routine commands misdirected its antenna. Now flight controllers are hoping to reposition the spacecraft, which is traveling between stars.
NASA on Tuesday picked up a "heartbeat signal" from the Voyager 2 space probe after it went silent late last month.
Voyager 2 was launched in 1977 to explore the outer planets of the solar system. It was designed to last 12 years but continued to beam data back to Earth for more than three decades.
However, late last month, flight controllers accidentally sent a wrong command causing the spacecraft's antenna to point away from Earth, making it unable to receive commands or transmit data.
NASA then used the Deep Space Network, its global network of giant radio antennas, to finally reestablish contact with the space probe on Tuesday.
"So we know the spacecraft is alive and operating," Voyager project manager Suzanne Dodd told the AFP news agency. "This buoyed our spirits."