A method and apparatus for refining a spacecraft state estimate, such as an attitude estimate or an angular velocity estimate, is disclosed. The invention provides for dual passageways in a laryngeal mask which permits a physician to effectively isolate the trachea from the esophagus. The system determines whether one of the plurality of data segments has been stored previously using a summary in a low latency memory; in the event that the data segment is determined not to have been stored previously, assigning an identifier to the data segment.