4. The investigation inquired into all the events which occurred prior to, during, and immediately following the engagement of Track Number (TN) 4131, later identified as Iran Air Flight 655. This designation of TN 4131 is used interchangeably with Iran Air Flight 655 throughout the investigation. There were specific, technically complex issues that required the Investigating Officer to call upon the professional expertise of the Commander, Naval Surface Warfare Center (NSWC), Dahlgren, and NAVSEA (PMS-400) personnel. The USS VINCENNES data recording tapes were hand delivered under chain-of-custody immediately following the incident to NWSC Dahlgren. After initial data reduction in the United States, technical representatives from NWSC Dahlgren, led by Head, AEGIS Program Office, and NAVSEA (PMS-400), representatives came to Bahrain and provided further analysis on the following matters:
a. AEGIS Weapon System Mark 7 performance and operation;
b. Performance and operation of the AN/SPY-1A radar;
c. Operation and message content in Link 11;
d. UPX-29 IFF operations;
e. Reconstruction of Command and Decision (C&D) console operator actions;
f. Comparison of tape data analysls with statements by operators;
g. C&D doctrine enabled and entered;
h. Internal voice configuration and capability; and,
i. Environmental effects on system performance.
5. As the investigation progressed, the statements and testimony of the witnesses were integrated into the timeline extracted from the data reduction, to form a chronology of the engagement. That chronology is attached to the hearing. Timelines became essential elements of the investigation, particularly as regards the short time period (minutes and seconds) in which the Commanding Officer was required to make his decision to fire. This time period is referred to as the "critical time period" throughout the report.
6. Because of a divergence between the recorded data on the USS VINCENNES's tapes and the recollection of the witnesses concerning what they saw and when they reported what they saw, a USN Medical Corps Team consisting of a psychiatrist and a physiologist were requested by the Senior Investigating officer to come to Bahrain. They arrived in Bahrain after the formal hearing closed. They were requested to determine whether the dynamics of the situation which confronted the crew of the USS VINCENNES impacted on their ability to perceive and relay the data which was available to them.
7. Certain items relevant to the investigation were not available to the Senior Investigating Officer. These items were primarily those which Iran could best provide (black box, recovery of wreckage, manifest, list of deceased, etc.). Requests for assistance through diplomatic channels were submitted via Commander in Chief, U.S. Central Command, to obtain
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