Descriptor attributes: The Type, DPL, S (system/user), and Present bits from the segment descriptor being loaded, held in a register called PROTUN. In a few cases, the Test PLA takes the 16-bit selector (segment register value) as input instead.
There is a plan to prevent such a strike—the Space Surveillance Network, a bevy of sensors that the military uses to track space debris. NASA monitors what’s unofficially known as the “pizza box,” a sort of no-fly zone around the ISS. When pieces of debris are predicted to enter the box—if there’s at least a 1 in 100,000 chance of collision—mission controllers order avoidance maneuvers, firing thrusters that move the ISS and dodge the trash. The technique has been used dozens of times since the first ISS module launched in 1998. But the system only tracks about 45,000 larger pieces, and all sensors have noise. Plus, risk thresholds can miss stuff, sometimes badly. In 2025, Chinese astronauts were briefly stranded at their station after debris hit their return vehicle.
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Matthew Bradley, an electrical and wiring operative, welcomed the opportunity to highlight the manufacturing work that is going on behind the factory walls as part of the exhibition.
Nasa announces change to its Moon landing plans