The Cassini orbiter, shown here in an artist's conception, has gone into safe mode of operation in advance of a flyby of Titan.
The Cassini orbiter has gone into a precautionary standby mode, a week in advance of a planned flyby of the Saturnian moon Titan, NASA reported Thursday.
Engineers at NASA's Jet Propulsion Laboratory said they don't expect Cassini to be back to normal in time for the Nov. 11 flyby, which was to focus on infrared mapping of the mysterious world's smoggy atmosphere. Scientists expected the bus-sized probe's camera to capture images of two prominent regions on Titan's surface, known as Shangri-La and Adiri.
NASA said Cassini entered safe mode at around 7 p.m. ET on Tuesday, curtailing the flow of science data and sending back only data about engineering and spacecraft health. Cassini is programmed to put itself in safe mode anytime it encounters a condition on the spacecraft that requires action from the folks at JPL's Mission Control in Pasadena, Calif.
"The spacecraft responded exactly as it should have, and I fully expect that we will get Cassini back up and running with no problems," Cassini program manager Bob Mitchell said in Thursday's mission status report. "Over the more than six years we have been at Saturn, this is only the second safing event. So considering the complexity of demands we have made on Cassini, the spacecraft has performed exceptionally well for us."
Since its launch in 1997, Cassini has put itself into safe mode a total of six times, NASA said.
The glitch was a downer for folks celebrating Deep Impact/EPOXI probe's successful flyby past Comet Hartley 2 earlier Thursday. "How I dread the words 'status report' from JPL," the Planetary Society's Emily Lakdawalla tweeted. But the status report added a bit of positive spin as well: "Cassini has 53 more Titan flybys planned in its extended mission, which lasts until 2017."
Update for 6:25 p.m. ET Nov. 5: During a follow-up phone call, Mitchell told me that engineers are "still looking at the data" to figure out exactly what was scrambled up in Cassini's electronic brain. But he has a pretty good idea what happened.
"We believe the cause is due to some data that got corrupted on its way from Earth to Saturn via the radio link," he said. "It was not a human error."
When Cassini came across the corrupted data, it went into safe mode, just as it's supposed to do. "The spacecraft is very tolerant of error," Mitchell said. "It'd be hard to break it."
But it takes a while to return the spacecraft to full operation after safing. Valves have been closed, science data traffic has been stopped, software flags have been set ... and Cassini's mission controllers have to make sure that the data corruption is completely fixed before they start up everything again. Otherwise the probe would merely return to safe mode.
In this case, mission team members concluded that the job could not be done in time for the Titan flyby, so instead they've decided to take advantage of the most opportune moment. The way it looks as of now, that moment will come on Nov. 24, when Cassini is due to start executing its next sequence of commands, Mitchell said.
More about Cassini:
- This is how Saturn's rings roll
- Slideshow: Cassini's greatest hits
- Titan may foreshadow Earth's desert future
- Visit Cassini at JPL | Cassini imaging team
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