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Rover Team Beaming New Commands to Opportunity on Mars
JANUARY 25, 2019

A Goldstone 111.5-foot (34-meter) beam-waveguide antenna tracks a spacecraft as it comes into view. The Goldstone Deep Space Communications Complex is located in the Mojave Desert in California. Engineers at NASA's Jet Propulsion Laboratory in Pasadena, California, will use antennas like this one to transmit a new set of commands to the Opportunity rover in an attempt to compel the 15-year-old Martian explorer to contact Earth.Image credit: NASA/JPL-Caltech. This photograph was taken on Jan. 11, 2012.

Engineers at NASA's Jet Propulsion Laboratory in Pasadena, California, have begun transmitting a new set of commands to the Opportunity rover in an attempt to compel the 15-year-old Martian explorer to contact Earth. The new commands, which will be beamed to the rover during the next several weeks, address low-likelihood events that could have occurred aboard Opportunity, preventing it from transmitting.

The rover's last communication with Earth was received June 10, 2018, as a planet-wide dust storm blanketed the solar-powered rover's location on Mars.

"We have and will continue to use multiple techniques in our attempts to contact the rover," said John Callas, project manager for Opportunity at JPL. "These new command strategies are in addition to the 'sweep and beep' commands we have been transmitting up to the rover since September." With "sweep and beep," instead of just listening for Opportunity, the project sends commands to the rover to respond back with a beep.

The new transmission strategies are expected to go on for several weeks. They address three possible scenarios: that the rover's primary X-band radio - which Opportunity uses to communicate with Earth - has failed; that both its primary and secondary X-band radios have failed; or that the rover's internal clock, which provides a timeframe for its computer brain, is offset. A series of unlikely events would need to have transpired for any one of these faults to occur. The potential remedies being beamed up to address these unlikely events include a command for the rover to switch to its backup X-band radio and commands directed to reset the clock and respond via UHF.

"Over the past seven months we have attempted to contact Opportunity over 600 times," said Callas. "While we have not heard back from the rover and the probability that we ever will is decreasing each day, we plan to continue to pursue every logical solution that could put us back in touch."

Time is of the essence for the Opportunity team. The "dust-clearing season" - the time of year on Mars when increased winds could clear the rover's solar panels of dust that might be preventing it from charging its batteries - is drawing to a close. Meanwhile, Mars is heading into southern winter, which brings with it extremely low temperatures that are likely to cause irreparable harm to an unpowered rover's batteries, internal wiring and/or computer systems.

If either these additional transmission strategies or "sweep and beep" generates a response from the rover, engineers could attempt a recovery. If Opportunity does not respond, the project team would again consult with the Mars Program Office at JPL and NASA Headquarters to determine the path forward.

For more information about Opportunity and the Mars Exploration Rover program, visit:


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Odp: [JPL] Rover Team Beaming New Commands to Opportunity on Mars
« Odpowiedź #1 dnia: Styczeń 28, 2019, 19:36 »
JPL still trying to contact Opportunity rover on Mars
January 25, 2019 William Harwood [Spaceflight Now]

Opportunity’s panoramic camera captured this self-portrait on Mars in 2014. Credit: NASA/JPL-Caltech/Cornell Univ./Arizona State Univ.

NASA’s Mars Opportunity rover landed on Mars 15 years ago this week, but the long-lived robot remains out of action in the wake of a global dust storm last summer that caused it to lose power. Engineers are still trying to contact the spacecraft, sending commands and listening for any sort of response, but hopes are fading, a senior manager said Friday.

“We’re getting close to the end,” said John Callas, the Mars Exploration Rover project manager at the Jet Propulsion Laboratory in Pasadena, Calif. “At some point, in an emotional sense, you have to say ‘enough’ and move on, to say goodbye.”

For many of the engineers and scientists that built and nurtured Opportunity over the years, the six-wheeled robot is almost a member of the family, and no one wants to say that final goodbye until every possible rescue option has been exercised. But seven months after contact was lost, that moment is approaching barring a sudden reversal of fortune.

“It’s just like a loved one missing in action, a pet that goes missing,” Callas said. “You spend several days searching the neighborhood, posting pictures on telephone poles, but then after six months, you say OK, we did all we could.”

But not quite yet.

It’s the windy season on Mars, and there remains a chance gusty breezes might blow off enough accumulated dust from Opportunity’s solar cells to allow its batteries to charge up enough for the spacecraft to phone home.

At the same time, flight controllers at JPL continue to send commands “in the blind” in an attempt to coax Opportunity back into action if it ever does wake up while NASA’s Deep Space Network antennas regularly listen for a response.

“We’ve been doing this strategy of listening with the DSN antennas as well as commanding to try to elicit a response from the vehicle,” Callas said. “The expectation was once the storm passed, that sunlight on the solar arrays would charge the rover back up and it would autonomously talk to us.”

But if the batteries were fully depleted, as now appears likely, the spacecraft’s internal clock would reset and “the rover won’t know what time it is,” Callas said. “And so, it’ll attempt to wake up at these odd hours of the day or night, so we might not hear from it when it is powered up because it’s got the wrong time.

“That’s part of the reason we were sending these commands. If the rover was ever awake, and it gets one of these commands, then it knows to respond right away.”

But so far, flight controllers have heard nothing.

Opportunity landed on Mars, on a plain known as Meridiani Planum, on Jan. 24, 2004, 15 years ago this Thursday. The design specifications called for a minimum 90-martian-day mission and an ability to rove at least 1,100 yards.

But Opportunity and its twin rover, Spirit, far exceeded expectations, chalking up year after year of slow-but-steady exploration, looking for signs of past habitability and confirming a warmer, wetter environment in the distant past.

Spirit got stuck in deep sand and ceased operations in 2011, but Opportunity pressed ahead, showing signs of wear and tear over the years but remaining in remarkably good health. Instead of the 1,100-yard design goal, the rover has covered more than 28 miles, marking its 5,000th day on the red planet last February.

But last June, a record dust storm boiled up, becoming a global event that shrouded the red planet in a thick haze, sharply reducing the amount of sunlight reaching Opportunity’s solar cells. Flight controllers last contacted the spacecraft on June 10.

“This was a historic dust storm,” Callas said. “Never since humans have been observing Mars and measuring the atmospheric opacity have we ever seen a dust storm this intense. … Essentially it was nighttime during the day on Mars.”

The storm persisted for weeks before finally dissipating. Relatively clear skies returned, but JPL has not been able to restore contact with Opportunity. In the meantime, the planet’s seasons are changing, temperatures are dropping and the amount of sunlight reaching Opportunity is decreasing.

“There are still some techniques we want to try to account for multiple failure scenarios on the vehicle,” Callas said. “We’re trying to look at all the possible things that could explain why we haven’t heard from the rover that are potentially recoverable. Things like if both transmitter amplifiers failed, could we use just the UHF (radio)? Those are the kinds of things we’re looking at. We’d like to give those a try.”

JPL is operated for NASA by the California Institute of Technology as a Federally Funded Research and Development Center, or FFRDC. As such, it receives payments from NASA in advance and currently remains in operation despite the ongoing partial government shutdown.

Callas said his small team will continue efforts to contact Opportunity until NASA is back in operation and able to provide guidance.

“NASA makes the decision about this,” he said. “Until they tell us otherwise, we’ll keep going.”


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Odp: [JPL] Rover Team Beaming New Commands to Opportunity on Mars
« Odpowiedź #2 dnia: Luty 15, 2019, 21:07 »
NASA declares Opportunity Mars rover mission over
by Jeff Foust — February 13, 2019 [SpaceNews]

NASA said Feb. 13 it was ceasing efforts to restore contact with the Opportunity Mars rover, ending its mission, originally slated to last 90 days, after more than 15 years. Credit: NASA/JPL illustration

WASHINGTON — NASA announced Feb. 13 that it was ending efforts to restore contact with the Opportunity Mars rover, bringing its mission to an end more than 15 years after it landed on the planet.

At an event at the Jet Propulsion Laboratory, project officials and NASA leadership said they were declaring the overall Mars Exploration Rovers project over after months of attempts by spacecraft controllers failed to reestablish communications with Opportunity after a major dust storm cut off power to the rover in June.

“I am standing here, with a sense of deep appreciation and gratitude, to declare the Opportunity mission as complete, and with it the Mars Exploration Rovers mission as complete,” said Thomas Zurbuchen, NASA associate administrator for science. That decision came after Opportunity failed to respond to a final set of commands transmitted to it by the Deep Space Network Feb. 12.

Opportunity last contacted Earth in early June as “an historic” global dust storm reached its location on Mars, said John Callas, project manager for the Mars Exploration Rovers at JPL. That storm darkened the skies and cut off of the rover’s solar power.

“We tried valiantly over these last eight months to try to recover the rover, to get some signal from it,” he said. However, the onset of winter at the rover’s location on Mars, a region called Perseverance Valley, meant less sunlight and colder temperatures, making it increasingly unlikely the rover could be recovered.

“It brought us to last night, and we sent our final commands, and we heard nothing,” he said. “So, it comes time to say goodbye.”

Opportunity was the second of the twin Mars Exploration Rovers to land on Mars, arriving in January 2004 about three weeks after Spirit landed. The rovers had 90-day lifetimes, but each far exceeded that. Spirit’s mission ended in May 2011 after traveling eight kilometers, while Opportunity logged 45 kilometers before losing contact last June.

Callas said the extreme longevity of the rovers could be credited in part to winds that cleared dust that had accumulated on the solar panels that, if not removed, would have diminished the power those panels generate. The rovers’ batteries also exceeded expectations, retaining 85 percent of their original capacity after more than 5,000 charge/discharge cycles.

A glitch with Opportunity that dates back to very early in its mission may have contributed to its demise. Callas said a heater in the rover’s robotic arm got stuck on shortly after landing, depleting the rover’s batteries during the night. “If we left it alone like that, the mission wouldn’t have lasted long beyond the 90 days,” he said.

To correct the problem, engineers developed a “deep sleep” mode to turn off all the heaters each night. When the dust storm hit, the loss of power “scrambled” Opportunity’s internal clock, keeping it from engaging that deep sleep mode each night. “It probably wasn’t sleeping at night when it needed to, and that heater was stuck on, draining away whatever energy the solar arrays were accumulating from the sun,” he said.

The JPL event was billed as a media briefing but was more of a celebration of the rover, with project scientists and engineers reminiscing about the mission. Only a few minutes at the end of the hour-long event was devoted to media questions.

Steve Squyres, the Cornell University planetary scientist who was principal investigator for the Mars Exploration Rovers, divided Opportunity’s mission into two parts. The first, lasting about nine years, covered initial exploration of its landing site, turning up evidence of water, albeit rather acidic, early in the planet’s history.

The project then made the decision to make a long trek to a distant crater, Endeavour. “When we got there the mission started all over again,” he said. That included finding evidence of past water on Mars that had a neutral pH, rather than acidic. “That was one of the mission’s most significant discoveries. It came 11 years into our 90-day mission.”

Asked later in the briefing whether either of the Mars Exploration Rovers might one day be retrieved to place in a museum, Squyres noted that huts from the early exploration of Antarctica, more than a century ago, have been preserved there. The same, he suggested, should be the case for the rovers. “We built them for Mars. That’s the place they were designed to go. That’s their home. That’s where I would like them to stay,” he said.

Another opinion, though, came from Ellen Stofan, a planetary geologist and director of the National Air and Space Museum. Speaking at the Commercial Space Transportation Conference here Feb. 13, shortly after the JPL event, she discussed ongoing renovations of the museum and plans for new exhibits.

“What I’m looking forward to in the museum, the artifact that I most want, is something from one of the Mars rovers that one of the first crews on Mars has been able to bring back to Earth,” she said. “I’ll put that right next to my Mars rock.”


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Odp: [JPL] Rover Team Beaming New Commands to Opportunity on Mars
« Odpowiedź #3 dnia: Luty 15, 2019, 21:09 »
Historic Opportunity Rover Mission on Mars Comes to Silent End
By Paul Scott Anderson, on February 13th, 2019 [AmericaSpace]

Opportunity casts its shadow in this image from sol 180 (July 26, 2004), taken by the rover’s front hazard-avoidance camera, on the edge of Endurance Crater. Photo Credit: NASA/JPL-Caltech]Opportunity casts its shadow in this image from sol 180 (July 26, 2004), taken by the rover’s front hazard-avoidance camera, on the edge of Endurance Crater. Photo Credit: NASA/JPL-Caltech

It’s been a long 15 years, but the inevitable has finally happened: the Opportunity rover’s days of exploring Mars are over. The sad news was announced this morning at 2 pm ET in a NASA press briefing, bringing an official end to one of the most successful Mars missions in history.

“It is because of trailblazing missions such as Opportunity that there will come a day when our brave astronauts walk on the surface of Mars,” said NASA Administrator Jim Bridenstine. “And when that day arrives, some portion of that first footprint will be owned by the men and women of Opportunity, and a little rover that defied the odds and did so much in the name of exploration.”

Opportunity, like its twin, Spirit, was designed for a hoped-for nominal mission of 90 Martian days (sols) when it landed in 2004, but lasted for an incredible 15 years. That is 60 times its projected life span.

The mission plan also called for Opportunity to travel at least 1,100 yards (1,000 meters), but ended up roving more than 28 miles (45 kilometers) altogether.

The last image ever sent back by Opportunity, on June 10, 2018, showing the darkened sky due to the dust storm. Photo Credit: NASA/JPL-Caltech/Cornell

“For more than a decade, Opportunity has been an icon in the field of planetary exploration, teaching us about Mars’ ancient past as a wet, potentially habitable planet, and revealing uncharted Martian landscapes,” said Thomas Zurbuchen, associate administrator for NASA’s Science Mission Directorate. “Whatever loss we feel now must be tempered with the knowledge that the legacy of Opportunity continues – both on the surface of Mars with the Curiosity rover and InSight lander – and in the clean rooms of JPL, where the upcoming Mars 2020 rover is taking shape.”

The trouble began in June 2018, when Opportunity’s location – and most of the planet – was hit with a massive dust storm. June 10 was the last time that the rover was heard from. Up until last night, NASA engineers sent over 1,000 radio commands to try to revive the rover, to no avail. The final transmission was sent via the 70-meter Mars Station antenna at NASA’s Goldstone Deep Space Complex in California.

“We have made every reasonable engineering effort to try to recover Opportunity and have determined that the likelihood of receiving a signal is far too low to continue recovery efforts,” said John Callas, manager of the Mars Exploration Rover (MER) project at JPL.

Eagle Crater, where Opportunity first landed on Jan. 24, 2004. The rover’s tracks can be seen on the right side of the image. Photo Credit: NASA/JPL-Caltech

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Opportunity: NASA Rover Completes Mars Mission. Video Credit: NASA/JPL

Opportunity had survived dust storms and other hazards before, but this time was different unfortunately.

It had been hoped that the rover simply “went to sleep” when the power in its solar panels became too low, and would revive later after the dust storm had ended. But it didn’t. Opportunity had also recently been in a period where stronger seasonal winds would blow off dust more easily, as had happened numerous times before, but that also did not work. So why didn’t Opportunity wake up?

As noted by Emily Lakdawalla on Twitter:

Emily Lakdawalla
 · Feb 13, 2019
Replying to @elakdawalla
Callas attributes the rover's longevity to 2 main technical things: the lucky seasonal winds providing dust-cleaning events, and the phenomenal overperformance of the lithium-ion batteries, which were at 85% capacity til the end.

Emily Lakdawalla
Ah, I hadn't realized this. Callas says that one plausible explanation for rover's failure now is that dust storm caused low power mode that scrambled its clock so it didn't know when to turn on deep sleep mode to preserve energy... 1/2
8:19 PM - Feb 13, 2019

Emily Lakdawalla
 · Feb 13, 2019
Replying to @elakdawalla
Ah, I hadn't realized this. Callas says that one plausible explanation for rover's failure now is that dust storm caused low power mode that scrambled its clock so it didn't know when to turn on deep sleep mode to preserve energy... 1/2

Emily Lakdawalla
...Opportunity (but not Spirit) had to go into a "deep sleep" mode every Martian night because one of the electric heaters in an arm joint was stuck on from landing day. If it didn't go into deep sleep, the stuck-on heater may just have drained the battery continuously. 2/2
8:20 PM - Feb 13, 2019

It may be that simple, that Opportunity just wasn’t able to be revived due to other mechanical and/or software problems, even if its solar panels had been cleaned off of dust.

Opportunity landed on Jan. 24, 2004 in Meridiani Planum, 20 days after its twin, Spirit, landed in Gusev Crater. Spirit kept exploring until May 2011, after it became stuck in deep sand and was unable to free itself.

Opportunity escaped its own similar predicament, Purgatory Dune, back in 2005.

Opportunity’s landing site was a treasure trove of geologic wonders, with bright patches of bedrock seen in the first images sent back. That bedrock provided evidence for past water in the region, as did the famous “blueberries” – hematite concretions, never seen before on Mars. Opportunity also found the first evidence for ancient salty playa lakes and groundwater on this now mostly-dry world. Important discoveries, since the rover’s overall mission was to determine the past habitability of this region of Mars.

Spirit and Oppy@MarsRovers
 Oppy proved beyond a doubt that ancient Mars had lots of liquid water. These hematite spheres, nicknamed "blueberries," formed in the presence of H2O. #ThanksOppy
8:16 PM - Feb 13, 2019

Spirit and Oppy@MarsRovers
 ...and we watched the skies darken.
Ultimately, it was the most intense dust storm in recorded Martian history that brought this epic mission to a close. #ThanksOppy
8:22 PM - Feb 13, 2019

“From the get-go, Opportunity delivered on our search for evidence regarding water,” said Steve Squyres, principal investigator of the rovers’ science payload at Cornell University. “And when you combine the discoveries of Opportunity and Spirit, they showed us that ancient Mars was a very different place from Mars today, which is a cold, dry, desolate world. But if you look to its ancient past, you find compelling evidence for liquid water below the surface and liquid water at the surface.”

The rover explored vast plains, deep craters and steep hills, and watched dust devils, as it continued its exploration over the years. Some of the most notable moments include:

 - Set a one-day Mars driving record March 20, 2005, when it traveled 721 feet (220 meters).
 - Returned more than 217,000 images, including 15 360-degree color panoramas.
 - Exposed the surfaces of 52 rocks to reveal fresh mineral surfaces for analysis and cleared 72 additional targets with a brush to prepare them for inspection with spectrometers and a microscopic imager.
  - Found hematite, a mineral that forms in water, at its landing site.
  - Discovered strong indications at Endeavour Crater of the action of ancient water similar to the drinkable water of a pond or lake on Earth.

“When I think of Opportunity, I will recall that place on Mars where our intrepid rover far exceeded everyone’s expectations,” Callas said. “But what I suppose I’ll cherish most is the impact Opportunity had on us here on Earth. It’s the accomplished exploration and phenomenal discoveries. It’s the generation of young scientists and engineers who became space explorers with this mission. It’s the public that followed along with our every step. And it’s the technical legacy of the Mars Exploration Rovers, which is carried aboard Curiosity and the upcoming Mars 2020 mission. Farewell, Opportunity, and well done.”

Dust devil seen by Opportunity on March 31, 2016. Photo Credit: NASA/JPL-Caltech

Opportunity’s final resting place, in Perseverance Valley on the edge of Endeavour Crater. This photo was taken by NASA’s Mars Reconnaissance Orbiter. Photo Credit: NASA/JPL-Caltech/Univ. of Arizona

“Opportunity’s final days were spent in Perseverance Valley, an ancient gully thought to have been carved by water or ice, on the edge of Endurance Crater.

“I cannot think of a more appropriate place for Opportunity to endure on the surface of Mars than one called Perseverance Valley,” said Michael Watkins, director of JPL. “The records, discoveries and sheer tenacity of this intrepid little rover is testament to the ingenuity, dedication, and perseverance of the people who built and guided her.”

Meanwhile, NASA’s other Mars rover, Curiosity, continues its mission in Gale Crater and the InSight lander is now ready to start investigating the deep interior of Mars.

Opportunity was beloved by many people – scientists and the public alike – and so became more than just a robot. This quote in Rebecca Boyle’s obituary to Opportunity sums it up nicely:

“It’s odd to think about grief being associated with a machine. But it’s a part of our lives.” – Mark Lemmon

More information about Opportunity is available on the mission website.


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Odp: [JPL] Rover Team Beaming New Commands to Opportunity on Mars
« Odpowiedź #4 dnia: Luty 15, 2019, 21:09 »
NASA declares Opportunity rover dead after 15 years on Mars
February 13, 2019 Stephen Clark [Spaceflight Now]

Opportunity’s front hazard-avoidance camera captured this image of the rover’s shadow July 26, 2004. Credit: NASA/JPL-Caltech

Eight months after last hearing from the Opportunity rover, NASA officials announced the end of the craft’s 15-year mission Wednesday, closing out an ambitious chapter of Mars exploration that proved the Red Planet once harbored running water and demonstrated the promise of mobile robotic scouts to survey other worlds.

The rover succumbed to a sky-darkening global dust storm, and last communicated to Earth on June 10, 2018. Mission officials hoped to regain contact with Opportunity after the dust storm cleared, but daily listening sessions and more than 1,000 tries to send commands to the rover produced no results.

Thomas Zurbuchen, head of NASA’s science mission directorate, declared the end of Opportunity’s mission in a press conference Wednesday at the Jet Propulsion Laboratory in Pasadena, California.

“I was there yesterday, and I was there with the team as these commands went out into the deep sky, and I learned this morning that we had not heard back, and our beloved Opportunity remains silent,” Zurbuchen said. “I am standing here with a sense of deep appreciation and gratitude to declare the Opportunity mission as complete, and with it the Mars Exploration Rover mission as complete.”

Opportunity landed on Mars on Jan. 24, 2004, to begin a mission that was not planned to last more than 90 days. Instead, Opportunity returned data for more than 14 years — nearly 60 times longer than its designed lifetime — and logged more than 28 miles (45 kilometers) on its odometer, farther than any other robot has driven on another world.

“I have to tell you, this is an emotional time,” Zurbuchen said.

Opportunity and its twin rover, Spirit, launched in 2003 from Cape Canaveral aboard a pair of Delta 2 rockets. After reaching the Red Planet in January 2004, both of the 384-pound (174-kilogram) rovers — each about the size of a golf cart — set out to explore their surroundings, climbing hills and descending into craters in search of geologic clues about the ancient history of Mars.

Spirit ended its mission in March 2010, after getting stuck in sand with its solar panels in an unfavorable orientation to generate power during a harsh Martian winter.

“We were meant to get to this point, to wear these rovers out, to leave behind no unutilized capability on the surface of Mars, but we had no idea it would take this long,” said John Callas, Opportunity’s project manager at JPL. “But even still, this is a hard day, and this is hard for me because I was there at the beginning.”

“Spirit and Opportunity may be gone, but they leave us a legacy, and that’s a legacy of a new paradigm for solar system exploration,” said Mike Watkins, director of JPL. “A robotic geologist on Mars, and an integrated science and engineering (and) operations team here on Earth all set out together on a mission of discovery. They didn’t know what they would find, they didn’t know what direction they would go, sometimes from one day to the next, and they made it work. And they made it work longer than any of us thought possible, by both brilliant scientific deduction of where to go and brilliant engineering to keep the rovers alive.”

“It’s a team that makes success like this,” Zurbuchen said. “It’s a team that creates exploration, transformative exploration, for science and engineering, and it’s a team that is celebrating here today, emotionally.”

Members of Opportunity’s ground team gathered late Tuesday to send the final commands to the rover in an attempt to restore communications. Credit: NASA/JPL-Caltech

Skies over the Opportunity rover blackened last June as a global dust storm enveloped Mars and starved the robot’s solar panels of sunlight. It was the most extreme dust storm observed by Spirit or Opportunity since their landings in 2004.

Ground controllers regularly listened for a call from Opportunity after losing communications with the rover, using giant dish antennas from NASA’s Deep Space Network to try and detect a signal. Engineers hoped the rover would automatically wake up and radio Earth when the dust storm cleared, but that did not happen. Managers then prepared commands to send up to Opportunity “in the blind,” hoping that a gust of wind would clear the solar panels of dust and bring the robot back to life.

Opportunity’s ground team sent up the last such command Tuesday night. After the signal took 13-and-a-half minutes to reach Mars — traveling at the speed of light — Opportunity should have sent a response back to engineers keeping vigil in a control room at JPL. Silence reigned.

“We tried valiantly over these last eight months to try to recover the rover, to get from signal from it,” Callas said Wednesday. “We’ve listened every single day with the Deep Space Network, with our sensitive receivers, and we sent over 1,000 recovery commands trying to exercise every possibility of getting a signal from the rover. But with time, the skies are darkening, it’s getting colder on Mars, we recently passed through the historic dust-cleaning season on Mars to see if that would help … That brought us to last night, we sent our final commands, and we heard nothing, so it comes time to say goodbye.”

NASA spent around $800 million — in 2003 economic conditions — to build and launch the Spirit and Opportunity rovers.

“Spirit and Opportunity were robotic field geologists,” said Steve Squyres, lead scientist for the twin rovers from Cornell University. “Geology is a forensic science. A geologist is like a detective at the scene of a crime. Something happened at this place on Mars billions of years ago. What was it? What was it like there back then? And you’re looking for clues, and the clues are in the rocks. So we equipped these vehicles with the tools that they needed to read those clues.”

Opportunity’s panoramic camera captured this self-portrait on Mars in 2014. Credit: NASA/JPL-Caltech/Cornell Univ./Arizona State Univ.

After a six-month journey from launch, Opportunity dropped to an airbag-cushioned landing at Meridiani Planum, a smooth equatorial plain, and rolled into a 72-foot-wide (22-meter) crater, a fortuitous interplanetary “hole-in-one” that presented scientists with a treasure trove of layered bedrock exposed by an ancient asteroid impact.

“The first day that we landed, it was geologic pay dirt right from the very beginning,” Squyres said.

“I remember the emotions,” Zurbuchen said. “I saw that Cornell professor (Squyres) jumping up and down like my 4-year-old on his birthday when entry, descent and landing was complete, and the rover said, ‘I’m here.'”

Within weeks, Opportunity discovered evidence that liquid water once flowed across the Martian surface at the Eagle Crater site.

“But it wasn’t nice stuff,” Squyres said Wednesday. “You know, we were running around saying, ‘Water on Mars! Water on Mars!’ It was really sulfuric acid on Mars. The pH was very low, this was very acidic stuff, it was very salty. This was not evidence of an evolutionary paradise, but it was a fascinating, fascinating environment.”

Opportunity drove to two bigger nearby craters — Endurance and Victoria — for an extended mission, then Squyres and his deputies decided to dispatch the rover across a barren stretch of Meridiani Planum, riddled with sand dunes, toward 14-mile-wide (22-kilometer) Endeavour Crater.

The cross-country trip took three years.

Opportunity’s navigation camera took this image of its tracks on the journey to Endeavor Crater on Aug. 4, 2010. Credit: NASA/JPL-Caltech

“When we got there, the mission started all over again,” Squyres said “New rocks, new stories, looking in the very distant past.”

“We were able, at the rim of Endeavour Crater, to find rocks that were probably the oldest observed by either one of the rovers,” he said. “And those told a story of water coursing through the rocks, but with a neutral pH. It was water you could drink, so we were about to piece together a new story there. That was one of the mission’s most significant discoveries, and it came 11 years into our 90-day mission.”

Opportunity took 217,594 raw images on Mars, nearly double the number captured by Spirit.

Abigail Fraeman, Opportunity’s deputy project scientist, was a junior in high school when the rover returned the first set of images soon after landing in Eagle Crater. She was at JPL for the landing, thanks to an educational project provided by the Planetary Society.

“It was those first images from Opportunity that inspired me to become a planetary scientist,” she said. “They revealed a view of Mars that we had never seen before.

“I’ve been hearing a lot of people’s stories,” Fraeman said. “What strikes me as so cool is that this story is not unique for me. There really are hundreds, if not thousands, of students who were just like me, who witnessed these rovers and followed along (with) their mission from the images they released to the public over the last 15 years, and because of that went to pursue careers in science, education and math.”

Callas counted the intergenerational team as “one of the most rewarding legacies” of the Spirit and Opportunity rovers. Scientists and engineers brought up with the Mars rovers will go on to support future space missions, such as the Curiosity rover still exploring Mars, or the Mars 2020 mission set for departure to the Red Planet next year, he said.

“We built them for Mars. That’s the place where they were designed to go. That’s their home, that’s where I would like them to stay. Also, if you had the opportunity to bring 180 kilograms of stuff back from the surface of Mars, the last thing I want to bring is something I know exactly what it’s made of,” joked Steve Squyres, Mars Exploration Rover principal investigator from Cornell University, in response to a question about retrieving the rovers and returning them to Earth.

“Why did these rovers last so long? Why did Opportunity last so long? There are two main technical reasons,” Callas said. “One is that we had expected that dust falling out of the air would accumulate on the solar arrays and eventually choke off power after about 90 days. But what we didn’t expect that wind would come along periodically and blow the dust off the arrays. This on a seasonal cycle actually became pretty reliable, and allowed us to survive not just the first winter, but all the winters we experienced on Mars, and to keep going and exploring.

“The other thing was that these rovers actually have the finest batteries in the solar system,” Callas said. “They had over 5,000 charge-discharge cycles on them, and they still had about 85 percent of their capacity. I mean, we’d all love it our cell phone batteries lasted this long, but that really was an enabling capability, that with the dust cleaning and the batteries allowed us to have that critical energy that we needed to get through the coldest, darkest parts of the winter on Mars, and to keep exploring.”

Opportunity suffered from a type of amnesia. A flaw in the rover’s flash memory forced ground controllers to retrieve imagery, science data and housekeeping telemetry before Opportunity went into hibernation every night, then start fresh again the next morning.

Multiple images from the Opportunity rover from June 2018 were stitched together to create this panoramic mosaic, days before the rover’s last contact with Earth. Credit: Credit: NASA/JPL/Cornell/Marco Di Lorenzo/Ken Kremer

“We had many challenges along the way,” Callas said. “When we first landed on Mars, one of the things that happened was we had a heater on the robotic arm on the rover that got stuck on. So every night that heater would come on and waste energy from the rover. If we left it alone like that, the mission wouldn’t have lasted long beyond the 90 days.

“So we developed this technique called deep sleep, which is every night we would turn everything off on the rover, including all the survival heaters, and the rover would get cold, but it would stay just warm enough that in the morning when the sun would come up, we would power everything back up,” he said. “It never got below its allowable temperatures.

“This is kind of like if you have a light in your bedroom stuck on, and you can’t sleep, so what you do is you go outside and you turn off the master breaker for your house,” Callas said. “But that means your refrigerator starts to warm up, but by the morning time when you wake up and you turn the breaker back on, the ice cream hasn’t melted too badly. And you do that every single night. Now imagine doing that for 5,000 nights. That’s what we had to do for this vehicle. But it also, partially perhaps, explains why we weren’t able to recover the rover.

If the rover’s batteries were fully depleted, its internal clock would have reset.

“With a loss of power, the clock in the rover gets scrambled, and it wouldn’t know when to deep sleep,” Callas said. “So it probably wasn’t sleeping at night when it needed to, and that heater was stuck on, draining away whatever energy the solar arrays were accumulating from the sun to charge those batteries. So that might be part of this explanation, in addition to the fact that now it’s much colder and darker on Mars (as winter approaches).”