Methods, systems, and apparatus are disclosed for high power thermal vacuum testing of satellite payloads using pick-up horns. Such pick-up horns can include at least one outer metal wall forming a metal body and at least one interior surface disposed in the metal body, forming at least one chamber in the metal body. The pick-up horn further includes a front metal surface disposed at a front end of the metal body, having at least one opening corresponding to the at least one chamber, and at least one high-power absorbing load disposed within the at least one chamber and in contact with the at least one interior surface. A pick-up horn may further include a serpentine coolant path disposed within the metal body between an outer surface of the at least one outer metal wall and the at least one high-power absorbing load. Related systems and methods are described.