S-III
From Halopedia, the Halo wiki
The CPOMZ file found on Colonel James Ackerson's computer was discovered in CASTLE Base by, Dr. Halsey. The file contained star charts and information on the Forerunner artifact found on Sigma Octanus IV. It also contained a full map of the CASTLE base facility on Reach that included a path to artifact, the Forerunner Crystal, beneath the surface of Reach.
