THE PARAMOUNT DUTY OF THE CLOUD ARK’S COMMANDER—SO IMPORTANT that Markus had broken character and described it to Ivy as "sacred"—was to stay on top of the Bolide Scan, which was a feed of information synthesized out of all of Izzy’s long-range radars and optical telescopes. A disproportionate number of GPop members devoted their lives to managing this, or to maintaining the equipment used to produce it. Because the stream of data was continuous, it needed to be broken down, for the consumption of someone like Markus or Ivy, into reports that showed up on their screens at regular intervals. A Triurnal Bolide Scan was issued at the top of each shift: dot 0, dot 8, and dot 16. Ivy read one of them when she woke up, another in the middle of her "afternoon," and the third just before going to sleep. Each of these summarized what was known about bolides that might come near them during the next eight hours, and made recommendations as to what maneuvers the Cloud Ark should execute in order to avoid them. Typically they made small burns several times a day for this purpose. The policy was "default go," which meant that the maneuver would be promulgated to the Cloud Ark via Parambulator, and carried out automatically, unless the commander vetoed it. The only reason this was ever likely to happen was in cases where two dangerous rocks were headed their way at about the same time and they needed to make a decision. Such events had occurred twice during the Hard Rain so far, but they had been simulated and war-gamed hundreds of times before that. The name of the game was to avoid getting cornered.