NASA's Farthest Flying Spacecraft Is Dying
The Voyager 1 spacecraft, nearly 25 billion kilometers from Earth, continues to experience problems as its power supply on board gradually runs out.
NASA engineers have successfully restored communications with Voyager 1, and the spacecraft is now operating normally after its dwindling power supply caused a signal loss for weeks. The problem began in October when the aging probe automatically switched off its X-band radio transmitter and began relying on the much weaker S-band radio transmitter to communicate with the mission team on Earth. As the most distant spacecraft from Earth, Voyager 1 is currently exploring interstellar space at a distance of 15 billion miles (24.9 billion km) , according to CNN .
Voyager 1 is flying in interstellar space. (Photo: Sci Tech Daily).
The probe automatically switched its transmitter when its onboard computer determined that Voyager 1 was running low on power after the team ordered one of its heaters to be turned on. The unexpected change prevented engineers from receiving information about Voyager 1's health, as well as the scientific data its instruments were collecting, for nearly a month. With some clever workarounds, the team successfully switched Voyager 1 and its X-band radio transmitter and began receiving daily data again in mid-November.
'The probes were never really designed to operate like this, and the team is learning new things every day,' said Kareem Badaruddin, Voyager mission manager at NASA's Jet Propulsion Laboratory in Pasadena, California. 'Fortunately, they were able to fix this.'
But that's just one of many challenges the mission team has faced in recent years as Voyager 1 and its twin probe Voyager 2 continue to explore space more than 47 years after they launched. The pair of probes, launched a few weeks apart in 1977, have outlived their original mission, designed to fly by the largest planets in the solar system for four years. They now fly in interstellar space, the only spacecraft operating outside the heliosphere, the bubble of magnetic fields and charged particles that extends beyond the orbit of Pluto.
Both spacecraft run on heat from decaying plutonium converted into electricity. The probes use about 4 watts of power each year, according to NASA, about the same as a small energy-saving light bulb. Crews began shutting down any systems that weren't vital to the probe's flight five years ago. Some of those systems include heaters that help keep the science equipment running at the right temperature. But to engineers' surprise, all of the equipment continued to operate, even at temperatures lower than they had been tested for decades.
Occasionally, engineers send commands to Voyager 1 to turn on some of its heaters and warm up parts that have been damaged by decades of radiation, said Bruce Waggoner, Voyager mission insurance manager. The heat can help reverse radiation damage that has degraded the performance of the spacecraft's components. But the command to the heaters on November 16 triggered the spacecraft's automatic error-correction system. If the spacecraft is using more power than it has available, it automatically shuts down nonessential systems to conserve energy. The team discovered the latest problem when it failed to receive a response from the spacecraft on October 18.
The two Voyager probes turned off all non-essential systems except for the science instruments, and the error-proofing system turned off the X-band transmitter and switched to the S-band, which uses less power. Voyager 1 had used the X-band transmitter for decades, but the S-band had not been used since 1981 because the signal was much weaker. The team had to search for the extremely weak S-band signal before they could restore communication with the spacecraft.
On November 7, engineers successfully transmitted the command to Voyager 1 to switch back to its X-band transmitter and begin collecting science data on November 18. They are now hard at work resetting the system that synchronizes Voyager's three computers. This is one of the last tasks to ensure Voyager returns to the way it was before the transmitter malfunction.
The transmitter change is just one of several initiatives NASA has taken to overcome communications challenges with the aging spacecraft this year, including firing thrusters to keep Voyager's antenna pointed toward Earth and developing a solution to a computer glitch that disrupted the probe's stream of science data back to Earth for months.
The Voyager team has computer models that help them predict how much power the spacecraft's heaters and instruments will use. But the fact that the heaters triggered the error-prevention system is a sign that the probe is nearing the end of its life and facing a more uncertain future.
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