STScI . SSO . Single Sign-On . ... What is STScI . ... Missions . ... Research . ... SSO" stands for "Single Sign-On" and it allows you to use your STScI SSO Portal credentials to log on to many services throughout the Institute. Rather than have each service maintain separate user accounts, users log in through the SSO Portal. ... Log in using your STScI email address (e.g. lastname@stsci.edu) and your "AD" password, the same password you use to access your email. ... Single Sign-On FAQ . ...