S.O.C.E., short for Subcommittee On Close Encounters and also known simply as the Contact Subcommittee, is a panel of researchers convened by the Galaxy Federation Government in T.C. 4754 (a year after the Miltian Conflict) to counter the Gnosis phenomenon. They are part of the Zohar Project until Episode III.
S.O.C.E. is based on Fifth Jerusalem, the planetary capital of the Federation. While it is called a "sub"committee, it has over 2000 members representing government agencies, corporations, and various scientific fields. Its operational core consists of seven members, each of whom holds high positions in the Federation. Juli Mizrahi is one of the seven members.
The U-TIC Organization has an operative within the S.O.C.E., which gave U-TIC an early warning when Ziggy infiltrated the Pleroma base to rescue MOMO Mizrahi as per S.O.C.E. command. This operative is seen speaking to Pellegri in Episode II until he is shot and presumably killed by Dmitri Yuriev.
S.O.C.E. itself does not play a role in the plot of Episode II and III instead, Juli Mizrahi acts on its behalf for most of the games. In Episode III, Allen Ridgeley notes that the Contact Subcommittee is no longer in charge of the Zohar Project, and has been transferred to the military and is now headed by Dmitri Yuriev.
After the disappearance of Fifth Jerusalem in Episode III, the committee is effectively gone, except for Juli who was not on the planet at the time.