ICE/ISEE-3 to return to an Earth no longer capable of speaking to it | The Planetary Society: How could this happen? Well, the fact that ISEE-3 is still broadcasting a carrier signal was actually an error; it should have been shut down. If they had planned for it to still be functioning at this point, they would have maintained the capability to communicate with it. I don't comprehend the intricacies of deep-space communications well enough to understand the obstacles here, and I don't question their conclusion, but that doesn't make me any less sad.
So ISEE-3 will pass by us, ready to talk with us, but in the 30 years since it departed Earth we've lost the ability to speak its language. I wonder if ham radio operators will be able to pick up its carrier signal -- 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.