For 17 years, it has been drifting on a lonely course through space. Launched during the disco era and shuttered by NASA in 1997, the spacecraft is now returning to the civilization that abandoned it.
It seemed destined to pass without fanfare, except for a slight chance of slamming into the moon, and then loop aimlessly through the inner solar system. But now, a shoestring group of civilians headquartered in a decommissioned McDonald's has reached out and made contact with it -- a long-distance handshake that was the first step toward snaring it back into Earth's orbit.
The zombie spaceship is coming home.
After 36 years in space, the craft, the International Sun-Earth Explorer-3, appears to be in good working order. The main challenge, the engineers say, is figuring out how to command it. No one has the full operating manual anymore, and the fragments are sometimes contradictory.
"We call ourselves techno-archaeologists," said Dennis Wingo, an engineer and entrepreneur who has a track record of extracting miracles from space antiques on which NASA has given up.
Mr. Wingo's company, Skycorp, has its offices in the McDonald's that used to serve the Navy's Moffett air station, 15 minutes northwest of San Jose, Calif. After the base closed, NASA converted it to a research campus for small technology companies, academia and nonprofits.
Mr. Wingo took on the project as if it were a stray puppy.
"No one else was going to do it," he said, "and it seemed like the right thing to do."
The race to revive the craft, ISEE-3, began in earnest in April. At the end of May, using the Arecibo Observatory radio telescope in Puerto Rico, the team succeeded in talking to the spacecraft, a moment Mr. Wingo described as "way cool." This made Skycorp the first private organization to command a spacecraft outside Earth orbit, he said.
Despite the obstacles, progress has been steady, and Mr. Wingo said the team should be ready to fire the engines within weeks.
NASA launched ISEE-3 in 1978. Jimmy Carter was president, the Commodores topped the music charts with "Three Times a Lady," and the No. 1 movie was "Grease," starring John Travolta and Olivia Newton-John. The craft orbited the sun between the sun and the Earth, allowing scientists to observe for the first time the high-speed stream of electrons and protons known as the solar wind before it reached Earth.
Then ISEE-3 was recruited to a different mission. With a serpentine do-si-do around the moon and Earth, it was aimed at Comet Giacobini-Zinner, passing through the tail in September 1985.
NASA used ISEE-3 for a few more observations of interplanetary space before retiring it in 1997. Since then, the craft has been looping around the sun on a 355-day orbit. Like a faster race car lapping the rest of the field, ISEE-3 will catch up to and pass Earth in two months.
That is exactly what Robert W. Farquhar, the craft's flight director, now 81, intended.
Mr. Farquhar, known for devising clever ways to move a spacecraft from point A to point B, came up with the intricate orbits that moved ISEE-3 to various locations in the solar wind, and then with the idea of using ISEE-3 to visit Giacobini-Zinner.
That angered the solar scientists, who accused him of stealing their spacecraft. But Mr. Farquhar won the support of NASA leaders. He also said he was just borrowing the craft and would return it.
After the successful Giacobini-Zinner flyby, ISEE-3 still had ample fuel, so three rocket burns in 1986 set it on a course to zoom about 30 miles above the surface of the moon 28 years later, on Aug. 10, 2014.
The gravitational pull of the lunar flyby would swing ISEE-3 into orbit around Earth. Mr. Farquhar suggested that a space shuttle could bring it to the ground. NASA even signed an agreement to donate the craft to the National Air and Space Museum.
The rest of NASA, however, was not looking that far ahead.
In 1999, the agency upgraded its Deep Space Network, the system of radio telescopes that communicates with distant space probes. The old transmitters that could talk with ISEE-3 were thrown away.
But ISEE-3 never was turned off, so while Earth lost its ability to talk to it, ISEE-3 still was broadcasting, waiting for its next command.
In 2008, the Deep Space Network listened briefly at the faraway spot where ISEE-3 was and heard the carrier frequency of the spacecraft's radio -- essentially a dial tone.
Two years later, NASA looked into reviving contact for the 2014 flyby but concluded that the scientific payoff would not be worth the effort and money. Fans of the old spacecraft persisted, arguing that it could be used to train future scientists and engineers. But in February, Leonard Garcia, a NASA employee who had set up a Facebook page promoting ISEE-3, conceded that it was not going to happen. New transmitters could be built, he wrote, "but it would be at a price no one is willing to spend." That caught Mr. Wingo's attention.
"Not only is it not impossible," he said, "I think it can work, and I know how to do it."
Mr. Wingo and Keith Cowing, the editor of NASA Watch, a sometimes cantankerous website covering news and gossip about the space agency, had previously collaborated on a project that resurrected equipment to read 50-year-old magnetic tapes, extracting high-resolution images taken by NASA lunar orbiters in the 1960s -- a task NASA had also regarded as infeasible. Mr. Wingo and Mr. Cowing decided ISEE-3 was another worthy effort.
About 20 others scattered around the country joined the effort, including many members of the original ISEE-3 team. On RocketHub, a crowdfunding website, they asked for $125,000 to help pay the costs. They collected nearly $160,000, from 2,238 donors.
Then they signed an agreement with NASA.