Earlier this year I caught wind of a campaign to raise funds to purchase hardware and develop software to then communicate with an abandoned satellite and bring into orbit near Earth. The International Sun/Earth Explorer 3 (ISEE-3) was launched on August 12, 1978. It’s original mission was to sit in an orbit around the Sun-Earth Lagrangian point (L1) and monitor various properties of the Sun, the Earth, and the interactions between the two.
In 1982, after completing it’s original mission, NASA repurposed it to chase down a comet and study it. Over a few years it made a series of maneuvers, making the most of it’s remaining fuel and gravity to slingshot around the moon and Earth and put it into an orbit around the sun with an eye towards Halley’s Comet.
By 1999 NASA ended the mission, powered down the satellite, and donated it to the Smithsonian. Or so they thought. In 2008 NASA found out that it had not been powered down and that all of its instruments, save one, were still operating. This presented an opportunity to take control of the satellite once more, move it back to L1 and let it continue to do science for however long its systems keep running.
One problem: NASA didn’t have the equipment to properly communicate with it anymore. After they thought it had been turned off in 1999, the necessary equipment was decommissioned.
Enter the ISEE-3 reboot project. A private group of scientists and engineers made a bid to take back control of the satellite by recreating the lost hardware using software-defined radio (SDR), in other words use a computer to simulate the physical hardware. Money was needed to fund development of the system as well as hardware to transmit the signal and to buy time on radio telescopes like the one at Arecibo Observatory (as made famous by the 1997 film Contact).
By the end of May the project was funded and the group immediately got to work. Within a month they were back in communication with ISEE-3 and began preparations to fire its thrusters and bring it back to L1. The entire project chronicled in their ISEE-3 Reboot blog.
This week, on Tuesday July 8, they attempted to make the Trajectory Correction Maneuver (TCM) to bring ISEE-3 to L1. Unfortunately the thrusters sputtered and died. The next day they tried to troubleshoot the problem as best you can from several hundreds of thousands of miles away. The diagnosis: the nitrogen gas used to pressurize the fuel tanks and force the fuel out of the tanks and into the thrusters had been depleted. The fuel is there, but without pressure it’s not going anywhere. The whole effort played out live on the ISEE-3 Reboot Twitter account.
So what now? The ISEE-3 Reboot team have put the satellite into science collecting mode. As long as its systems allow, it will continue to collect data and transmit it back to Earth. Unfortunately it will eventually head back out towards the sun and be too far for us to listen to it in a cost effective manner. We’ve got about three months until it’s too far away and so they’ll make the most of it.
And maybe in another 30 years it’ll come back and we can listen once again, for a few months, about what else ISEE-3 can see.