I followed up with Leonard Garcia, who has been one of the leaders of the attempt to regain control of ISEE-3, to ask what, in fact, the cost was. He told me that when the Deep Space Network realized what was going to be involved in regaining this capability, they did not even proceed as far as developing a cost estimate; "they decided this wasn't going to be possible."

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.