Kerberos is one of four natural satellites of Pluto. It is the moon where the Kerberos Mission crew consisting of Shiro, Samuel Holt, and Matthew Holt, were reported missing five months after leaving Earth and presumed dead due to pilot error. They were, in truth, captured by the Unnamed Galra Commander some time after landing on Kerberos while collecting ice samples, and taken as prisoners of the Galra Empire. These humans are the first to travel so distantly through Earth's solar system. Shiro is the only known crewmember to escape alive a year after his capture.
According to Pidge, it takes the futuristic technology of Earth spacecrafts "months" to reach Kerberos. Samuel Holt implies it takes two months when he describes how the crew will be eating freeze-dried peas for that amount of time. The Blue Lion and pursuing Galra warship travel from Earth to Kerberos in a matter of minutes. To contrast, New Horizons, launched in 2006, took 9.5 years to reach Pluto.