A crowd-funded team of "citizen scientists" hopes to contact, reactivate and take over control of a long-retired 35-year-old science probe as it passes by Earth later this summer, an innovative grass-roots effort inspired as much by science as the thrill of attempting something that "is just so cool."
If the takeover attempt works -- and no one yet knows whether the aging spacecraft is healthy enough to resume normal or even limited operations -- the team plans to fire up the probe's rocket engine to break out of solar orbit, using a close flyby of the moon to put the craft into a gravitationally stable near-Earth parking zone.
If all that works, the team hopes to resume limited science operations, using the spacecraft's surviving instruments to study Earth's space environment.
"We're just trying to bring this down to a level where anybody can help us save a spacecraft and anybody can use what comes from it," said Keith Cowing, a former NASA employee who maintains the widely-read NASA Watch website.
"Why not? What else are you going to do with it? It also might serve as an inspiration to some folks to say well, if we can do it with that spacecraft are there others out there?"
The International Sun/Earth Explorer 3 spacecraft, or ISEE-3, was launched in 1978 to study the solar wind and its interaction with Earth's magnetosphere. After completing its primary mission, the spacecraft was maneuvered into an orbit around the sun and repurposed to study comets, flying through the tail of Giacobini-Zinner in 1985 and collecting long-range data on Halley's Comet in 1986.
In 1991, the hardy spacecraft began yet another mission, studying cosmic rays and solar activity, moving slightly faster than Earth in a similar orbit. NASA officially ended the mission in 1997, shutting down the probe's instruments but leaving its radio transmitters on. They've been sending out a carrier signal ever since.
In August, ISEE-3 will make its closest approach to Earth in 30 years, prompting Cowing and Dennis Wingo, a space entrepreneur, to consider what, if anything, might be done to recover and reactivate the spacecraft.
"We were just talking about it, we did some calculations and talked to a few people and realized that this was something that was actually quite doable," Cowing said.
After reviews of hard-to-find documentation and more detailed discussions with a broad range of engineers and scientists, they approached NASA for permission to attempt re-contact and re-activation. The space agency "didn't say no" and discussions continued.
But NASA was not expected to provide funding and the ISEE-3 Reboot Project still had to come up with the money to build a transmitter that could "talk" to the spacecraft, cover the costs of software development, travel and a variety of other items. The team turned to the public, setting up a RocketHub crowd funding effort with a goal of raising $125,000.
"We had another telecon with NASA, with a whole bunch of people in the room, and they said well, we're not going to say no," Cowing said. "We said, well fine, our crowd funding starts on April 14 at 11 a.m."
Within a few days, more than $20,000 had rolled in "and all the jaws were on the floor at NASA," Cowing said. The original target later was increased to help cover the cost of using NASA's Deep Space Network and as of this week, more than $150,000 had ben raised.
Cowing said contributors came from all walks of life and that most of them were not "space people." The motivation seemed to be "why not? Why not try this? It's just so cool," Cowing said. "They're from all over the world. I've got 2,000 donors and two thirds of them have given 10 or 50 bucks. ... It just sort of took on a life of its own."
The Reboot team plans to send commands to the ISEE-3 spacecraft using a German transmitter at the Aercibo Observatory radio telescope. If they can establish communications, they will attempt to send commands to stabilize the probe's spin and fire its engine for a long sequence of "burns" to drop out of solar orbit.
Based on data from NASA's last communication with the spacecraft in the late 1990s, engineers believe enough fuel is on board to change the probe's velocity by a total of nearly 500 feet per second, or about 335 mph. That should be enough to set up a close lunar flyby, using the moon's gravity to help maneuver the craft into a near-Earth parking slot.
But the lunar flyby will pose yet another challenge.
"The spacecraft is already going to go by the moon," Cowing said. "But we want to bring it a little closer, within 50 kilometers (31 miles), and dip it around the back side. But since the spacecraft's battery is dead, it has been for decades, the moment the sunlight stops pretty much everything shuts off. And it's never been off. So this is kind of an Apollo 13 moment."
But Cowing is optimistic the Reboot team can pull it off.
"The spacecraft's transmitters are on, we've detected both of them," he said. "That means A, the transmitters work and B, they're getting electricity from somewhere because the batteries died 20 years ago. So the solar cells and the power collection and distribution system work.
"And last time the spacecraft was talked to, of the dozen instruments (on board) about two thirds of them had either full or partial functionality. The odds are, these things are still working. There's no computer on there, just pretty much a processor for commands. Your toaster is smarter. But it knows what to do if you tell it what to do."
Asked if the goal was to resume science or just prove that it could be done, Cowing said "it's both."
"Why not try it? We told people up front it's iffy, and we've gotten over $150,000 now from people and they knew exactly what the risk was. And, it's cool. The factor that's motivated a lot of people is 'why not?'"
As for the potential science, "we're going to do our best to make sure whatever comes back from that spacecraft is on line as fast as we can get it online, that it's open to anyone."