Phase Change Cells

Temperature sensor calibrations drift over time. On the ground, high-accuracy sensors are typically recalibrated on an annual basis. Until recently, sensors on long space missions could not be recalibrated to International Standards. SDL has developed a phase change cell (Miniature Orbital Temperature Reference-MOTR) to recalibrate temperature sensors while on orbit.


  • Maintains the accuracy of electro-optical sensors by enabling blackbody source on orbit to be recalibrated to absolute standards
  • Phase transition measurements repeatable to better than 3 mK
  • Phase change transitions are monitored independently of the host blackbody
  • Small size, working designs can fit inside a one inch cube and weigh less than 15 g
  • Pure materials on the ITS-90 scale or custom eutectic materials to achieve desired temperature


ISS MOTR Test Cell

International Space Station Miniature Orbital Temperature Reference Test Cell

The ISS MOTR test cell demonstrated that gallium melts at the same temperature in microgravity as it does on the ground and can be stored for long periods of time without a noticeable change in the melt temperature.