'My battery is low and it's getting dark:' End of Opportunity mission a loss for team

More than 1,000 commands had been sent since the golf-cart sized Opportunity rover fell silent on June 10, 2018, the victim of a historic global storm which engulfed Mars. NASA declared the mission complete at a Feb. 13 press conference at the Jet Propulsion Laboratory in Pasadena, Calif.

The rover likely experienced multiple faults as dust plunged its location on the west rim of Endeavour Crater near Mars’ equator into darkness. Opportunity’s solar panels were unable to keep instruments and heaters functioning to maintain communication with NASA and keep the rover alive. On the opposite side of the planet, the Curiosity rover reported an overnight low of -97 degrees Fahrenheit. Lows haven't risen above the -70s since then.

Opportunity’s last message to Earth included measurements of power production (21 watt-hours, down 97% since the storm began) and atmospheric opacity (10.8 vs. the normal tau of 0.5 and less than the 2.0 required to produce sufficient power). Those close to the program described what the rover was telling us more simply: “My battery is low and it's getting dark”.

Each mission is more than the robotic hardware exploring nearly five light minutes away, it’s a team of people. For the scientists asking questions and engineers building and operating the hardware to help find answers, "Oppy" had become a part of their family.

Tactical Uplink Lead Keri Bean tattooed “(tau)=10.8”, the final measurement of how much sunlight was reaching the solar cells, on her arm. Bean, a storm-chaser as a meteorology student, joked about sending the rover chasing dust devils and the dust storm that ultimately terminated the mission.

The tendency to anthropomorphize "Oppy" began early, when Sofi Collis, a then 9-year old immigrant won an essay contest to name the MER rovers before their 2003 launch. She wrote of dark, cold and lonely nights in a Siberian orphanage: “I looked up at the sparkly sky and felt better. I dreamed I could fly there. In America, I can make all my dreams come true. Thank you for the Spirit and the Opportunity.”

"Oppy" set endurance records, traveling more than 28 miles to make deliveries more than 50 times during the 90-Sol primary missions because of the people dedicated to keeping them going. She developed a robotic form of arthritis when a small motor in her robotic arm began stalling. Years later, her memory began failing and onboard software started reporting aches and pains in her right front and center wheels.

Engineers used the MER Surface System Testbed, her earthbound twin better known as “Dusty”, to find solutions to these aging problems and keep the science flowing. These efforts continued to be evident in the Science Operations Working Group (SOWG) meetings where science operations were planned each day.

During the last SOWG meeting I attended at JPL, rover driver Paolo Bellutta leaned over periodically to translate phrases like “salute”, the raising of the robotic arm to clear it out of the way of the panoramic camera, necessary since 2012. Paolo and his team also developed backwards driving techniques to help relieve wheel stress.

"I am from Italy, but please no jokes about driving”, he adds.

On February 12, mission team members past and present gathered at the Space Flight Operations Facility, JPL's mission control for its interplanetary and deep space missions. Rover drivers, scientists, engineers and project managers joined NASA’s associate administrator, Dr. Thomas Zurbuchen, and Opportunity’s principal investigator, Steve Squyres, to watch Bean send the final set of commands, then wait for a response each knew was unlikely to come.

The data stream began as others had, with a wake-up song. Squyres selected the final song, Billie Holiday’s “I’ll Be Seeing You”. Previous selections during the months long vigil to contact the rover included Tom Petty’s “I Won’t Back Down” and Kansas’s “Dust in the Wind”. 

As they waited, Bean, an avid Star Wars fan, passed out what planetary geologist Dr. Tanya Harrison described as "emotional support porgs". Harrison called the gesture "a beautiful reminder that these robotic missions, at their core, are wholly human," in her account of the evening in Medium.

About 30 minutes later, the quartet of commands had been radiated from the giant dish at NASA’s Deep Space Network communication facility 100 miles to the northwest in Goldstone, Calif. Earth’s rotation brought similar giant dishes in Canberra, Australia into position to listen for a response that never came.

Project Manager John Callas thanked the technicians​​​​​​​ of the Deep Space Network "for over fifteen and a half years of outstanding support from launch until tonight.", adding "this concludes operations for MER1, spacecraft ID 253". Canberra operators responded "MER Project is off the net" and it was done.

Opportunity’s team gathered again following the press conference to toast the mission. The Mars InSight team had coincidentally picked the same Pasadena restaurant to celebrate successfully deploying the final instrument on that recently landed mission. As the two teams joined together, Dr Fred Calef, officially a Geospatial Information Scientist for the Mars Curiosity mission but more commonly known as the “Keep of the Mars Maps”, put it best: “This is the way it is. Mars exploration continues on.”