Voyager 2 in Trouble?

These six narrow-angle color images were made from the first ever ‘portrait’ of the solar system taken by Voyager 1, which was more than 4 billion miles from Earth and about 32 degrees above the ecliptic. Credit: NASA/JPL

NASA engineers have commanded the Voyager 2 probe to limit its transmissions to Earth, and only send back information on its health and status. This order was sent out after the spacecraft’s pattern of communication unexpectedly changed.

Voyager 2 is currently at the edge of our solar system, about 13.8 billion kilometers, or 8.6 billion miles, from Earth. Preliminary engineering data received on May 1 show the spacecraft is basically healthy.

Engineers believe the source of the puzzling change is the flight data system, which is responsible for formatting the data to send back to Earth. The change in the data return pattern has prevented mission managers from decoding Voyager 2’s science data.

The first changes in the return of data packets appeared on April 22, but engineers had to wait until April 30, after the spacecraft had executed a planned roll maneuver, before they could send commands to Voyager 2. The spacecraft is so far away that it takes nearly 13 hours for signals to reach the spacecraft, and nearly 13 hours for Voyager 2’s response to reach NASA’s Deep Space Network on Earth.

Voyager 2 launched on August 20, 1977, about two weeks before its twin spacecraft, Voyager 1. The two spacecraft are out at the edge of the heliosphere, the bubble the Sun creates around the solar system, making them the most distant human-made objects.

This artist’s rendering depicts NASAs Voyager 2 spacecraft as it studies the outer limits of the heliosphere – a magnetic ‘bubble’ around the solar system that is created by the solar wind. Credit: NASA/JPL-Caltech

Voyager 1 has traveled farther than Voyager 2 – it is currently about 16.9 billion kilometers (10.5 billion miles) away from Earth. Voyager 1 is in good health and performing normally, and mission managers are looking forward to the time when Voyager 1 leaves our solar system and enters interstellar space. This event is projected to occur in the next five years or so, with Voyager 2 on track to enter interstellar space shortly afterward.

The original goals for the two Voyager spacecraft were to explore Jupiter and Saturn, but the mission was extended, and they are still returning data 33 years later.

The Voyager ‘Golden Record’. Credit: NASA

As part of a mission extension, Voyager 2 flew by Uranus in 1986 and Neptune in 1989, taking advantage of a once-in-176-year alignment to take a grand tour of the outer planets. Among its many findings, Voyager 2 discovered Neptune’s Great Dark Spot and 450-meter-per-second (1,000-mph) winds. It also detected geysers erupting from the pinkish-hued nitrogen ice that forms the polar cap of Neptune’s moon Triton. Working in concert with Voyager 1, it also helped discover actively erupting volcanoes on Jupiter’s moon Io, and waves and kinks in Saturn’s icy rings from the tugs of nearby moons.

One of the most famous images taken by the Voyager mission was not of our distant planetary neighbors, but of Earth. Our planet appears as a speck of light in the vast darkness of the solar system. This was the image that inspired Carl Sagan to call our home planet "a pale blue dot."

As he wrote in a book by that name, "That’s here. That’s home. That’s us. On it everyone you love, everyone you know, everyone you ever heard of, every human being who ever was, lived out their lives. … There is perhaps no better demonstration of the folly of human conceits than this distant image of our tiny world."

Ed Stone, Voyager project scientist at the California Institute of Technology in Pasadena, remarking on the important observations made by Voyager 2, said, “We will know soon what it will take for it to continue its epic journey of discovery."

UPDATE: May 24, 2010
One flip of a bit in the memory of an onboard computer appears to have caused the change in the science data pattern returning from Voyager 2, engineers at NASA’s Jet Propulsion Laboratory said. A value in a single memory location was changed from a 0 to a 1. Engineers reset the flipped computer bit on Wed., May 19, and engineering data confirmed the reset was successful. The spacecraft resumed sending properly formatted science data back to Earth on Sunday, May 23.