“Well, it sounds like they are coming back,” Doob said.
“Yeah, unless—”
“Unless what?”
“Unless he just wants to hang out at L1. That would be a hell of a lot safer. I don’t think any moon shards are going to make it out that far.”
Doob reread the message.
“You’re right,” he said. “All he says is that they’re thrusting. Nothing about transferring back to low Earth orbit. Then he asks for a situation report.” He put his hands over his face and rubbed it. “I’m fading,” he announced. “I should be Skyping my family right now.”
“Get outta here,” Dinah said. “I can work on the report. And I can encrypt it, now that you showed me how it works.”
Doob pushed off and drifted to the exit, then caught himself and turned back. “I could figure this out myself,” he said, “but it’s late. Maybe you know off the top of your head. If Sean goes into that transfer orbit from L1 to here, how long before he shows up?”
“Thirty-seven days,” Dinah said.
“About seventeen days into the Hard Rain,” Doob said. “Awkward timing.”
Dinah looked back at him. She didn’t say a word, but he knew what she was thinking: If only awkward timing were the worst of our problems.
“Okay,” Doob said. “Thanks, Dinah.”
“Next time,” she said, and made a drinky-drinky motion with her thumb and pinkie.
“Next time,” he agreed, and pushed through the curtain.
Dinah checked the time. Now that she knew roughly where Ymir was, she understood the timing of the transmissions. During a certain part of each ninety-three-minute orbit, Izzy was on the wrong side of the Earth, and couldn’t receive Sean’s signal. Following each blackout period was a window during which they could talk. They had just burned a window taking down his transmission and decrypting it, and were about to go into blackout again. During that span of time Dinah should be able to write a short message and get it encrypted using the next one-time pad.
What to write wasn’t entirely clear. She could provide some obvious data like the number of arklets currently in orbit, the number of people, how many robots she had up and running. But she suspected that Sean wanted a different kind of information. He wanted to know what would happen were he to show up, thirty-seven days from now, with a mountain of ice. The Cloud Ark could use it, that was for sure. Likewise, Sean needed the Cloud Ark; two guys on a spaceship pushing a giant ball of ice was not a sustainable civilization. But Sean was going to be cagey. He was going to want something. He would want to make a deal.
He would want to make a deal with Dinah’s boyfriend.
One step at a time. Just sending him a few basic stats would occupy the next transmission window. Rather than driving herself crazy worrying about the longer game, Dinah focused on that through the next blackout period, writing up a message as tersely as possible and then encrypting it using Doob’s Python script.
The L1 point of the Earth-sun system was located on a straight line between those two bodies. Ymir, for all practical purposes, was at L1. So, generally speaking, when Izzy swung around the dark side of the Earth and emerged into the sunlight, it meant that they could “see” L1, and communicate with Ymir. This next occurred at about 7:30 A.M. Greenwich time, which happened to be sunrise in London. Dinah, gazing down out her little window, was able to see the terminator—the dividing line between the day and night sides of Earth—creeping over the Thames estuary down below, and lighting up a few tall spires in the London financial district. Then she turned to her telegraph key, established contact with Ymir, and tapped out her message. This ended up consuming the entire transmission window. She had to send the characters very slowly, because Sean wasn’t very good at reading Morse code. And because the message was encrypted, he wasn’t able to guess missing letters from context, and so every letter had to be read clearly. By the time she was finished, Izzy had swung almost halfway around the world and was about to plunge back into night. She finished her transmission with TBC, which she hoped they would understand as “to be continued,” then went right back to work writing and encrypting a supplement.
She was getting ready to open another broadcast window, a little before 9:00 A.M. London time or “dot 9” in Izzy-speak, when Ivy floated in without knocking.
“I want to look out your window,” she announced.
“That’s fine,” Dinah said. “What’s up?” Because obviously something was up. Ivy’s face looked funny. And she had said “your window,” not “your window.”
“What’s so special about my window?” Dinah asked.
“It’s next to you,” Ivy said.