Team members want to eventually place ISEE-3 in the Earth-sun Lagrange Point 1 (ES-1), a gravitationally stable spot about 930,000 miles (1.5 million kilometers) from Earth. Cowing said it might be August or September before that happens, but the timeline isn't firmed up yet.
If all goes to plan, the spacecraft will also head behind the far side of the moon for about 25 minutes, which is somewhat risky given there's no working battery. Cowing pointed out, however, that the spacecraft has done it before, and said they will likely leave the instruments on to give it a bit of extra heat as it passes behind.
Communications Challenges Keeping track of the spacecraft will be somewhat more difficult as it approaches Earth, because its position changes more rapidly from our viewpoint. Right now the team is remotely using the massive fixed-dish Arecibo Observatory in Puerto Rico.
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Within a week, they hope to have supplemental communications at Morehead State University, although the first engine firing at least will likely take place with Arecibo.
Meanwhile, at least a couple of amateurs have been able to track ISEE-3's radio communications using small dishes. As the spacecraft gets closer to Earth, Cowing said he is curious if university optical telescopes will be able to pick out the small craft. (It's about 15 million to 20 million miles away, and moving closer at about a quarter-million miles a day, he said.)
Cowing said that he is amazed at how healthy the spacecraft is. "It's almost like people going to the Antarctic, and discovering something somebody left behind half a century ago, frozen, still works."
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