LOS ANGELES, July 9 (Xinhua) -- The U.S. space agency NASA is implementing a new plan to keep its Voyager 1 and 2 spacecrafts, its oldest explorers, to continue working, according to a release of NASA's Jet Propulsion Laboratory (JPL).

NASA's Voyager 1 and 2 spacecraft have been flying for nearly 42 years -- longer than any other spacecraft in history. To ensure that these vintage robots keep working, mission engineers have been working on plans to manage them, particularly the instruments and thrusters.

One key issue is that both Voyagers, launched in 1977, have less and less power available over time to run their science instruments and the heaters that keep them warm in the coldness of deep space.

Engineers have had to decide what parts get power and what parts have to be turned off on both spacecrafts.

After extensive discussions with the science team, mission managers recently turned off a heater for the cosmic ray subsystem instrument (CRS) on Voyager 2 as part of the new power management plan, according to the JPL.

Mission team members can now preliminarily confirm that Voyager 2's cosmic ray instrument is still returning data, despite dropping to a chilly minus 74 degrees Fahrenheit (minus 59 degrees Celsius), according to the JPL.

Another Voyager instrument also continued to function for years after it dropped below temperatures at which it was tested, said the JPL.

"It's incredible that Voyagers' instruments have proved so hardy," said Voyager Project Manager Suzanne Dodd. "We're proud they've withstood the test of time. The long lifetimes of the spacecraft mean we're dealing with scenarios we never thought we'd encounter."

According to the JPL, Voyager 2 continues to return data from five instruments as it travels through interstellar space. Voyager 1, which crossed into interstellar space in August 2012, continues to collect data from its cosmic ray instrument as well, plus from one plasma instrument, the magnetometer and the low-energy charged particle instrument.