Three decades after it drifted away, millions of kilometres from Earth, a vintage space probe has returned and is being revived, to be put back in service through a crowdfunded initiative by space science enthusiasts.
It is the latest chapter in the remarkable story of the ISEE-3 scientific spacecraft. It was launched nearly 36 years ago, was reconfigured into a comet-chasing platform, then sailed out of radio contact with Earth for a decade until it re-emerged in 2008, when its orbital path dragged it back towards our planet.
On Thursday, a group of scientists gathered at their own initiative at the Arecibo radio telescope in Puerto Rico re-established two-way communications with the spacecraft and started to command it to send data about the state of its onboard systems.
"SUCCESS! We are now in command of the ISEE-3 spacecraft!" the team tweeted at 4 p.m. before confirming by Thursday evening that ISEE-3 was transmitting telemetry again.
To resurrect ISEE-3, they had raised nearly $160,000 from 2,238 online donors, pored over old NASA documents and programmed software-defined radio devices to link up with a spacecraft whose communications hardware had long been retired from service on Earth.
The National Aeronautics and Space Administration had agreed to let the private group – which calls itself the ISEE-3 Reboot Project – take control of its wayward spacecraft.
"We have a chance to engage a new generation of citizen scientists through this creative effort," astrophysicist John Grunsfeld, a former astronaut who is now associate administrator for NASA's Science Mission Directorate, said in a communiqué announcing the agreement.
The ranks of the ISEE-3 Reboot Project include Dennis Wingo, president of the aerospace engineering company SkyCorp, and Keith Cowing, a former NASA astrobiologist.
The group has engineering students in their 20s and a space guru, 81-year-old retired NASA mission designer Bob Farquhar.
Dr. Farquhar, an expert in orbital mechanics, has been a key character in ISEE-3's storied life.
The ISEE (International Sun-Earth Explorer) program was an international 1970s project to study solar wind and the Earth's magnetosphere.
The ISEE-3 spacecraft was launched on Aug. 12, 1978, in the days when disco still dominated the airwaves and the Montreal Canadiens won the Stanley Cup every spring.
It travelled to the Lagrangian 1 libration point – a stable spot where the gravitational pull of the sun is balanced by that of the Earth and its moon – about 1.5 million to 1.6 million kilometres from our planet.
By 1982, with ISEE-3 having completed its prime observation mission, Dr. Farquhar came up with a new goal for the spacecraft.
The famous Halley's Comet, which revisits the solar system every 75 to 76 years, was expected back in 1986. The Soviet Union, the European Space Agency and Japan had readied missions to study Halley but a cash-strapped NASA had no planned flights to the comet.
Dr. Farquhar devised a way to steer ISEE-3 through a complex trajectory (on a graphic it looks like a tangle of noodles) towards another approaching comet, Giacobini-Zinner.
During an 18-minute pass in 1985, ISEE-3, which had been renamed ICE (International Cometary Explorer), crossed the Giacobini-Zinner comet's tail, collecting data that could be used as a benchmark for the Halley missions of the following year.
After being directed upstream of Halley to gather more observations, ISEE-3 moved increasingly far away and eventually drifted out of reach for reliable radio reception. The last contact was in 1999.
Nearly a decade later, in the fall of 2008, one of the antennas of NASA's Goldstone Deep Space Communications Complex, in California's Mojave Desert, picked up a signal from ISEE-3.
The spacecraft's orbit was taking it closer to Earth again and now Dr. Farquhar suggested that, in the summer of 2014, when the probe would be close to the moon, it could be redirected back to its original mission, observing the sun from the Lagrangian 1 libration point.
However, in a case of history repeating itself, NASA is again going through budgetary hard times. In April, senior NASA officials decided they could not fund a revival of the ISEE-3 project. Four days later, a private initiative began.
It wasn't the first time outsiders came to rescue a NASA deep-space project. In 1980-81, a grassroots campaign called the Viking Fund collected $100,000 to make sure NASA would have enough money to keep analyzing the data from its Viking 1 Mars lander.
This time, it was even more challenging because the project only had a month to start raising money and try to find a way to recontact ISEE-3.
Earlier this month, they reached their initial $125,000 fundraising target. Ten days ago, they started getting beacon signals from the approaching spacecraft.
Now, they will test its systems so that later this summer they will refire its thrusters, swing it by the moon and send it on to a new mission.