Juan was an engineer aboard the ECS Horizon.

He greeted Travis Mayweather during the latter's return to the Horizon in January of 2153. Although his captain (and Travis' brother), Paul Mayweather, did not approve of Travis' suggestion to upgrade the Horizon, especially its weapons system, Juan would assist Travis in making modifications to the Horizon so it could defend itself against pirates who were attacking the Horizon. With the upgrades, the ship was able to defend itself and drive off the attacking ship. (ENT: "Horizon")

Juan was played by actor Philip Anthony-Rodriguez.
In the final draft script of "Horizon", Juan was described as being in his "30's".