"Nothing went wrong with it," Hu said. "It had bad data. I will show you." With a few taps on his tablet he brought up a three-dimensional model of Izzy on the big screen above the conference table. To a first approximation, this seemed reasonably up to date; it depicted modules and space vehicles that had been added to the complex only within the last couple of days. "This is the model that the system was using yesterday for collision avoidance."