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 McDonalds have 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 that NASA has given up on. Mr. Wingo’s company, Skycorp, has its offices in the McDonalds that used to serve the Navy’s Moffett air station, 15 minutes northwest of San Jose, California. After the base closed, NASA converted it to a research campus for small technology companies, academia and nonprofits.

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. This made Skycorp the first private organisation 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.

After its launch in 1978, 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.

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.

In 1999, NASA 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 was never turned off. So while Earth lost its ability to talk to it, ISEE-3 was still 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. Mr. Wingo’s stepped in at this point. He was joined by Keith Cowing, the editor of NASA Watch, a website covering news and gossip about the space agency, and about 20 others scattered around the country, 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.

If everything goes as hoped, ISEE-3 will end up in its original location to observe solar wind. — New York Times News Service