The mission team of NASA’s Jupiter-orbiting Juno spacecraft executed a deep-space move in December 2023 to repair its JunoCam imager to capture photos of the Jovian moon Io. Results from the long-distance save were presented during a technical session on July 16 at the Institute of Electrical and Electronics Engineers Nuclear & Space Radiation Effects Conference in Nashville.
JunoCam is a color, visible-light camera. The optical unit for the camera is located outside a titanium-walled radiation vault, which protects sensitive electronic components for many of Juno’s engineering and science instruments.
The graininess and horizontal lines seen in this JunoCam image show evidence that the camera aboard NASA’s Juno mission suffered radiation damage. The image, which captures one of the circumpolar cyclones on Jupiter’s north pole, was taken Nov. 22, 2023.
This is a challenging location because Juno’s travels carry it through the most intense planetary radiation fields in the solar system. While mission designers were confident JunoCam could operate through the first eight orbits of Jupiter, no one knew how long the instrument would last after that.
Throughout Juno’s first 34 orbits (its prime mission), JunoCam operated normally, returning images the team routinely incorporated into the mission’s science papers. Then, during its 47th orbit, the imager began showing hints of radiation damage. By orbit 56, nearly all the images were corrupted.
Long Distance Microscopic Repair
While the team knew the issue may be tied to radiation, pinpointing what, specifically, was damaged within JunoCam was difficult from hundreds of millions of miles away. Clues pointed to a damaged voltage regulator that is vital to JunoCam’s power supply. With few options for recovery, the team turned to a process called annealing, where a material is heated for a specified period before slowly cooling. Although the process is not well understood, the idea is that the heating can reduce defects in the material.
“We knew annealing can sometimes alter a material like silicon at a microscopic level but didn’t know if this would fix the damage,” said JunoCam imaging engineer Jacob Schaffner of Malin Space Science Systems in San Diego, which designed and developed JunoCam and is part of the team that operates it. “We commanded JunoCam’s one heater to raise the camera’s temperature to 77 degrees Fahrenheit — much warmer than typical for JunoCam — and waited with bated breath to see the results.”
Soon after the annealing process finished, JunoCam began cranking out crisp images for the next several orbits. But Juno was flying deeper and deeper into the heart of Jupiter’s radiation fields with each pass. By orbit 55, the imagery had again begun showing problems.
“After orbit 55, our images were full of streaks and noise,” said JunoCam instrument lead Michael Ravine of Malin Space Science Systems. “We tried different schemes for processing the images to improve the quality, but nothing worked. With the close encounter of Io bearing down on us in a few weeks, it was Hail Mary time: The only thing left we hadn’t tried was to crank JunoCam’s heater all the way up and see if more extreme annealing would save us.”
View This Story in Real-Time Space
Test images sent back to Earth during the annealing showed little improvement the first week. Then, with the close approach of Io only days away, the images began to improve dramatically. By the time Juno came within 930 miles (1,500 kilometers) of the volcanic moon’s surface on Dec. 30, 2023, the images were almost as good as the day the camera launched, capturing detailed views of Io’s north polar region that revealed mountain blocks covered in sulfur dioxide frosts rising sharply from the plains and previously uncharted volcanos with extensive flow fields of lava.
Testing Limits
To date, the solar-powered spacecraft has orbited Jupiter 74 times. Recently, the image noise returned during Juno’s 74th orbit.
Since first experimenting with JunoCam, the Juno team has applied derivations of this annealing technique on several Juno instruments and engineering subsystems.
“Juno is teaching us how to create and maintain spacecraft tolerant to radiation, providing insights that will benefit satellites in orbit around Earth,” said Scott Bolton, Juno’s principal investigator from the Southwest Research Institute in San Antonio. “I expect the lessons learned from Juno will be applicable to both defense and commercial satellites as well as other NASA missions.”
More About Juno
NASA’s Jet Propulsion Laboratory, a division of Caltech in Pasadena, California, manages the Juno mission for the principal investigator, Scott Bolton, of the Southwest Research Institute in San Antonio. Juno is part of NASA’s New Frontiers Program, which is managed at NASA’s Marshall Space Flight Center in Huntsville, Alabama, for the agency’s Science Mission Directorate in Washington. The Italian Space Agency, Agenzia Spaziale Italiana, funded the Jovian InfraRed Auroral Mapper. Lockheed Martin Space in Denver built and operates the spacecraft. Various other institutions around the U.S. provided several of the other scientific instruments on Juno.
More information about Juno is at: