because of bad weather at the launch pad. Most countdown schedules also include some pre-planned built-in holds. These provide an opportunity to perform non-launch activities, handle unexpected issues, or to catch up on the schedule if it is running long.

Under some circumstances, a countdown may be recycled to an earlier time. When that happens, launch personnel begin following the countdown checklist from the earlier point.

During countdown:
* Aerospace personnel bring the rocket

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