Trajectory control programs in support of Apollo missions

The trajectory control programs ensure the integrity and consistency of all trajectory data that is used by the flight controllers on space flights. This means that the ephemeris, which is used for many of the calculations of trajectory data, must be updated in a timely manner with no interference from other tasks. It also means that users of the ephemeris must be protected from trajectory updates that might make their data inconsistent. The objective is achieved by an elaborate queue control process that continually enables and disables various real-time queue control blocks to regulate the independenttask processing.