In-situ sampling of Near-Earth Asteroids (NEAs) has the potential to enable a considerably greater understanding of the formation of the Solar System. A significantly difficult aspect of a sample return mission to an asteroid is the variable thermal environment that the spacecraft has to endure. For a spacecraft to survive, appropriate radiator placement is necessary for internal heat rejection. Since the craft is also required to land on the asteroid, which radiates intense IR fluxes, the placement of the radiator on an asteroid lander is not straightforward. An analysis was performed into potential areas on an asteroid lander that may be useful for the location of a radiator. It was found that an asteroid-facing radiator would be ineffective, whilst radiators located on the sides and top may be plausible under specific conditions. An analysis of how the radiator temperature would vary when a rendezvous with an asteroid occurred was also performed. It was found that if a spacecraft landed on an asteroid for only a few seconds, then due to the landing process on the NEA's surface there would be a minimum of 2-3oC radiator temperature change from the original starting position and that the longer the landing time the higher this temperature change became. New relationships were derived between the radiator temperatures of a craft situated on the asteroid's surface and the thermal characteristics of the asteroid. An equation for the average power required by a spacecraft located on a rotating asteroid was developed, enabling the thermal engineer to swiftly estimate basic asteroid lander characteristics. The guidelines and equations derived are of additional value to the thermal asteroid lander engineer as they can also be utilised for more detailed thermal design if parameters for specific missions are employed.