Today's XKCD comic is based around a wonderful story of a space craft sent to explore Earth, and later a comet, in 1978, which is finally returning to Earth.
And it's even more wonderful because - as it turns out - it's totally true.
The ICE/ISEE-3 craft was indeed launched in 1978, before completing its initial mission to explore our magnetosphere with lots of fuel and working instruments still remaining.
The craft was repurposed in 1983 to go and study two comets, and it's been in a heliocentric orbit ever since which - later this year, in August - will bring it back around to Earth again.
And as XKCD points out, however, that's where the tragedy starts. Because if Nasa still had the equipment we would be able to talk to ISEE-3 and - depending on how many of its instruments are still working (12 were working when we last looked in 1999) repurpose it again, and send it on another mission.
Alas, it is not to be. As the XKCD comic again makes clear, Nasa doesn't have the necessary transmitters to send the ISEE-3 craft a signal, or even to listen in to its data stream and understand what we hear.
The old-fashioned equipment was finally removed in 1999. And that would seem to be that. Nasa says it's just not feasible to put the equipment back together, or build new ones. It's just too expensive - which is where the XKCD imagines the internet stepping in.
Then again, there was some truth to that too.
Valiantly, the ISEE-3 Returns group tried to find a way to build new working transmitters. But - woe - it recently abandoned its efforts after months of work, saying they were unable to carry out the work single handed, with no funding:
"This effort has always been risky with a low probability of success and a near-zero budget. It is thanks to a small and dedicated group of scientists and engineers that we were able to get as far as we have. Thank you all very much."
After 30 years, ISEE-3 will pass us by waiting for a signal, for orders - for something. But we won't even be able to say hello. We'll just wave, watch, and let it pass by.
Emily Lakdawalla at Plantary.org, who has written often about the project, ended her most recent piece with a poignant farewell:
"I wonder if ham radio operators will be able to pick up its carrier signal," she wonders. "It's meaningless, I guess, but it feels like an honorable thing to do, a kind of salute to the venerable ship as it passes by."