Abstract: A method for on-orbit calibration of the temperature sensors of a blackbody is disclosed. The method may include selecting a blackbody traveling in a micro-gravity environment and comprising a sensor, a container positioned proximate the sensor and containing a material, and a heat transfer device positioned proximate the at least one container. The heat transfer device may transition the material through a phase change. The temperature sensor may monitor the temperature of the material during the phase change. Additionally, the state of the material may be measured by displacement of the container to improve the accuracy of the plateau temperature measurement. A correction may be calculated to correct any disparity between the temperature reported by the temperature sensor during the phase change and the known plateau temperature, measured at a threshold state of the material, corresponding to that phase change.