A citizen science effort to revive a middle-aged spacecraft has come to a close after the probe's rockets failed to fire.
But there may be life in the old spacecraft yet, says Keith Cowing of space news site NASA Watch, who helped spearhead the rescue effort.
"It's not a zombie, it's not a Flying Dutchman, it just ran out of gas," Cowing says. "The stereo still works and so does the air conditioner."
The International Sun-Earth Explorer 3 (ISEE-3) launched in 1978 as a joint US and European mission to study how the solar wind, a flood of charged particles from the sun, interacts with our planet's magnetic field. It originally orbited at the L1 Lagrange point – a spot between the sun and the Earth where their combined gravitational forces effectively cancel out so smaller objects can hold still.
But in the mid-1980s, ISEE-3 left its home base to orbit the sun and chase comets Giacobini-Zinner and Halley. The spacecraft was supposed to shut down in 1997, but surprisingly, the international Deep Space Network received a signal from it in 2008.
Deep space revival
Cowing and Dennis Wingu of the aerospace firm Skycorp decided to crowdsource a rescue mission to reinstate ISEE-3in its original job. They raised nearly $160,000 in an online crowdfunding campaign, and partnered with NASA to communicate with the craft for the first time in decades on 19 May.
The team hoped to order the craft to fire its engines and return to its orbit near Earth earlier this week. But after a few successful pulses, the craft's thrusters stopped responding.
"The spacecraft was doing everything we told it to, except there was no fuel, so no oomph," Cowing says. "It was literally the last gasp from the propulsion system."
Nine of the original 13 science instruments still work and are transmitting data on interplanetary magnetic fields and cosmic rays, Cowing says. The solar panels are also working better than expected, and monitoring their health could help inform more modern solar panel designs.
The team is marshalling radio telescopes around the world to keep listening to ISEE-3 as a "citizen science Deep Space Network", Cowing says. And even if the spacecraft's trajectory around the sun, which is uncertain at the moment, takes it out of range, Cowing hopes to try to revive other vintage spacecraft that had been left for dead and use them for citizen science projects.
"We had too much fun with this one not to try it again," he says.
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