MARCO-B, also known as MarCO-B, is a CubeSat (6U) satellite designed and manufactured by JPL for communication and data relay missions, particularly in interplanetary contexts. Launched on May 5, 2018, from AFWTR SLC3E using an Atlas V 401 launch vehicle, MARCO-B has a length of 0.3 meters, diameter of 0.2 meters, and span of 0.8 meters. It carries equipment including a UHF/X-band transponder and an engineering camera. The satellite's dry mass is 13.5 kg and its power system consists of solar cells and batteries. Equipped with propulsion for maneuvering, MARCO-B has four axial 25 mN thrusters and four RCS 25 mN thrusters. Its operational lifetime exceeds one year.