A daunting three-hour presentation to NASA management on the future of the MAVEN Mars orbiter was supposed to be the biggest challenge for the mission team earlier this year. But just as the presentation was going smoothly on Earth, the spacecraft itself was in serious trouble millions of miles away.
As she finished leading the presentation that day in February, Shannon Curry, recently appointed Principal Investigator for the MAVEN mission, felt confident in the work of the team, arguing that the March The mission should continue for at least another three years, an argument based on six months of exhaustive work by the team.
Then his phone rang. “We finally finish the presentation, I turn everything back on and our project manager calls me immediately,” Curry told Space.com. “Now I think he’s calling me and saying, ‘Congratulations, you did it, you’re great,’ and he’s saying, ‘We’re in safe mode.'”
Safe mode means that a spacecraft has encountered a problem that it cannot solve on its own, so it has shut down everything it doesn’t need to survive until engineers come to grips with it. activate. Earth can assess the situation. Sometimes the solution is simple, the cosmic equivalent of restarting an internet router.
But not this time.
“The safe mode event was — catastrophic is too strong, but I mean, we almost lost the spacecraft,” Curry said, calling the incident “incredibly serious” and “scary.” And when the team wanted to celebrate the end of the six-month mission expansion campaign, the timing stung. “It was like taking your breath away. On your birthday.”
MAVEN, more officially known as Mars Atmosphere and Volatile Evolution, arrived in orbit around the Red Planet in 2014. Since then, the spacecraft has not only studied the Martian atmosphereas its name suggests, but also served as a key relay station for communications between NASA and its Mars landers and rovers, which cannot report Earth directly.
It’s not a mission NASA wants to end, and indeed, at the end of the review process that culminated in the grueling presentation, the agency authorized the mission keep working for three years. However, MAVEN has been in space for over eight years, far longer than expected, and one part in particular is causing the team trouble.
The spaceship transports two of what engineers call inertial measurement units, or IMUs: a primary version, called IMU-1, and an identical backup called IMU-2. Whatever IMU the spacecraft is using at any given time is responsible for keeping MAVEN in the correct attitude or orientation in space. (Attitude is crucial: Functions such as charging solar panels and communicating with Earth cannot occur properly when a spacecraft loses attitude.)
After worrying issues with the IMU-1 surfaced in late 2017, the MAVEN team switched the spacecraft to its backup unit. But late last year, the team noticed that the IMU-2 unit was starting to wear out much faster than expected. So, in early February, the team returned the spacecraft to its original IMU-1 unit.
Two weeks later, on February 22, the same day MAVEN’s mission expansion was presented, the spacecraft suddenly didn’t appear to be using either IMU to position itself properly.
“For different reasons, our two [IMU]”s started showing problems,” Curry said. “When we went into safe mode, it was because one of them really crashed, basically, and the other one was just losing its life.”
The first challenge was to stabilize the spacecraft, which required a procedure engineers called heartbeat arrest.
The term “isn’t just for dramatic effect: it’s basically like ripping the cord out of the wall,” Curry said. “The spacecraft restarted its main onboard computer, then when that didn’t work it had to switch to the backup computer, and we had never been on the backup computer before.”
After more than an hour of spacecraft trying to revive the IMU-1, the computer swap, which also put MAVEN on the IMU-2, held. And it’s not too soon: the spacecraft’s focus on the sun was beginning to drift, an existential threat in itself.
But even after the MAVEN team had solved the most pressing issues, the situation remained dangerous, because the team knew that using the IMU-2 was heading for disaster. “We have one IMU left, and we don’t have a lot of time on it. At all,” Curry said. “We recovered from safe mode and then we were still in pretty hot water.”
Race to sail by the stars
So the team set to work developing what spacecraft officials call “all-stellar mode.” This mode allows the spacecraft to determine its attitude by matching the stars he sees with his inner map of the cosmos. It’s not as accurate as using an IMU, but its lifespan is not limited. Unfortunately, the All-Stellar mode takes time to develop. The MAVEN team intended to do this work later this year. “We had already bookmarked it for October as ‘just in case,’ thinking we were doing our extra credit homework,” Curry said.
The spaceship had other ideas. Once MAVEN was stable on IMU-2, the team rushed to develop the all-stellar mode as quickly as possible, completing the process in time to send the relevant commands to the spacecraft on April 19, just under two months after the onset of the crisis.
For about a month after the all-stellar implementation, the MAVEN team gradually began turning on and checking the instruments, although the spacecraft had to remain pointed at Earth throughout the time, limiting the science what the mission could do.
Curry particularly regrets the loss of data from MAVEN’s extreme ultraviolet instrument, which cannot observe at all when the spacecraft is pointing at Earth. Among other things, this instrument can measure certain types of ultraviolet radiation and X-rays from the Sun upon arrival on the red planet.
And while MAVEN was recovering, the sun produced several major flares that the spacecraft missed. “It’s a real kick,” she said. “A few X-class flares have spread beyond Mars and impacted Mars, and MAVEN is the only one that could observe them and couldn’t.”
The slow resumption of full operations also meant that MAVEN spent another month unable to serve as a relay satellite for the InSight lander and the Curiosity and Perseverance rovers, the three NASA robots currently active on the Martian surface. Although other satellites are also involved in this work, MAVEN bears one of the greatest burdens. So the three-month outage of the spacecraft meant not only a reduction in MAVEN science, but also a reduction in Mars science as a whole.
“It’s been very difficult for all the surface assets,” Curry said. And in turn, the rescue was much more than MAVEN itself. “It wasn’t just to make sure we saved our spacecraft. It collected a lot of data about Mars in general.”
Back to work
After more than three months out of service, MAVEN finally resumed normal operations on Saturday May 28, according to a statement from the Laboratory of Atmospheric and Space Physics at the University of Colorado at Boulder, where the mission headquarters is located. But this milestone doesn’t mean the spacecraft team’s work is done.
While all-stellar mode can get the job done for normal operations, it’s not accurate enough to safely see MAVEN through its trickiest maneuvers, and the spacecraft still has precious little time left on its IMUs. .
“We have to spend this summer and the next year or two finding really smart ways to stop using the IMU when we normally would,” Curry said. “If we did nothing, we wouldn’t be successful in the next 10 years.” (The recent mission expansion sees the spacecraft through 2025, but NASA has said it wants to use MAVEN’s relay capability on its Mars sample return mission campaign, which is currently targeting delivery to Earth in 2033.)
Curry said she was confident the MAVEN team could meet this challenge as well. “When all of a sudden you’re faced with this, frankly, existential threat of saying, ‘Get it figured out or you’re going to lose the spaceship,’ people get it. And so we have a way forward, we have a bunch of ideas to start testing,” she said. “Is that all set? No. It’s going to take a lot more work to find clever ways to do that. But again, it’s a very, very, very creative and smart team.”
In the meantime, now that MAVEN is back to normal operations, there is valuable science to be done regarding the atmosphere of Mars. In particular, Curry is excited to see upcoming data that will show how the atmosphere is responding to the sun’s increasing activity. The sun’s activity fluctuates over an 11-year period solar cyclewith the star rising now that scientists predict it will peak around 2025.
“The solar cycle is just getting started right now and we’re still at least 18 months away from peaking, so we couldn’t be more excited to get back into full gear,” Curry said.
And the 2025 solar maximum is particularly intriguing because scientists expect it to coincide with the Red Planet’s next seriousness. dust storm season. During the Southern Hemisphere summer, weather conditions can trigger dust storms so large that some encompass the entire planet. It’s now dust storm season on Mars and MAVEN has also looked at previous seasons, but the alignment of the cycles raises the stakes.
“MAVEN will see the most extreme conditions it has ever seen, as there will be dust, so it is a bottom conductor, and then extreme solar activity as the top conductor,” said Curry said of the tantalizing 2025 opportunity. “We can’t wait to get back to it.”
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