When the Spacecraft Goes Silent, Engineers Awake

The New Horizons mission to Pluto suffered glitches that had to be solved 4.67 billion miles away.

The New Horizons interplanetary space probe went silent on July 4, 2015, just a week before the craft was scheduled to begin delivering photos and data from Pluto. After 9.5 years traveling to the far off once-planet, there was suddenly nothing. At first, the 40 members of the Space Mission Operations Group that manages NASA's New Horizons mission were stunned.

New Horizons, NASA, spacecraft

Yet according to Alice Bowman, New Horizons Mission Operations Manager (MOM) at the Johns Hopkins University Applied Physics Laboratory in Maryland, there wasn’t time for panic. When asked about the team’s emotional response during the hours it looked like the mission might possibly be doomed, she told Design News, “We didn’t have time for an emotional reaction. We had to get to work.”

The malfunction occurred just as the spacecraft was approaching Pluto. “The flyby was scheduled for nine days, from July 7 to July 16. This nine-day sequence took up 80% of our memory,” said Bowman. “On July 4th we stared loading the sequence to the spacecraft. The set of commands took two hours to radiate. At 1:55 pm, we lost communication with the spacecraft. That happened right at the time everybody was interested.”

Over the next few days, the team explored a number of scenarios that might have caused the glitch. “We thought the problem could be the switch from the main computer to the backup, so we switched to the backup computer. This was at 3:11 pm on July 4th,” said Bowman. “We have a process we follow when we have anomalies. We pretty much knew what to do. Over the next couple days, we got it back into configuration with four hours to spare. We didn’t leave the Command Center for three or four days, but that’s what made it successful.”

Maryland, We’ve Solved the Problem

The malfunction took days to solve simply because of the distance from Earth to Pluto, 4.67 billion miles. Communication with the craft to fix the malfunction was maddeningly slow at 4.5 hours each way. And that’s at the speed of light. The team would receive a response to communication nine hours after sending a message. The team discovered the spacecraft experienced a software anomaly and went into safe mode, preventing it from performing scientific observations.

Team engineers went to work to resolve the problem, and on July 5, NASA announced that the problem was determined to be a timing flaw in a command sequence used to prepare the spacecraft for its flyby. The spacecraft resumed scheduled science operations on July 7. The science observations lost because of the anomaly were judged to have no impact on the mission's objectives.

15 Years And the Project’s Still Going

Bowman told the dramatic story of the New Horizons Pluto mission in a keynote presentation at ESC Silicon Valley last week. The project has been operating for 15 years. “We proposed a mission to Pluto. Many projects were proposed but they were not funded. In 2001 NASA funded the mission. From the launch of the spacecraft, it would take 9.5 years to reach Pluto. We launched in 2006, expecting to reach Pluto in 2015.”

New Horizons, NASA, spacecraft

Since the spacecraft would travel billions of miles from the sun, the team had to find a non-solar power solution. “Power was an issue, since the sun was too far away for solar. We used nuclear and had to get permission from the Department of Defense,” said Bowman. “The ship is about the size of a baby grand piano. We built it to have no moving parts because it had a long voyage and we wanted to minimize what might break.”

Discoveries and Changes on the Way to Pluto

Along the way, developments continued on Earth. “In 2005, we discovered the two moons of Pluto. We had a competition for naming them. Any name proposed had to be consistent with the name of Pluto of the underworld,” said Bowman. In another development during the journey, Pluto was demoted. “Eight months after we launched, the IAU [International Astronomical Union] met and decided to redefine what was a planet. Pluto was declassified as a planet.”

New Horizons, NASA, spacecraft

Even though the trip to Pluto took 9.5 years, the spacecraft was breaking speed records. “We wanted to get to Pluto as fast as we could,” said Bowman. “The New Horizons spacecraft became the fastest manmade object moving at 36,000 miles per hour. We passed the moon in nine hours.” The speed breaks down to 600 miles per minute, a dizzying 10 miles per second.

 

 

Bowman continues to lead the Space Mission Operations Group for the New Horizons mission. The spacecraft is continuing to send data back as it moves beyond Pluto. Bowman expects the craft to stay in communication with Earth until at least 2035.

Rob Spiegel has covered automation and control for 17 years, 15 of them for Design News. Other topics he has covered include supply chain technology, alternative energy, and cyber security. For 10 years he was owner and publisher of the food magazine Chile Pepper.

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