The Passive Radiative Cooler is a three-stage unit designed to cool two Focal Plane Assemblies to 83K: the Long-wave and the Short/Mid-wave. At the same time, the Passive Radiative Cooler will reject 136mW of power. The Passive Radiative Cooler weighs 11 kilograms, and is composed of aluminum, Kel-F, magnesium, Invar, glass-epoxy thermal isolators, and stainless steel.
The Passive Radiative Cooler operates in three stages; cold, intermediate, and first. In the cold stage, the temperature can drop as low as 74K under no-load conditions. In the intermediate stage, the temperature stabilizes at 130 K, and finally, in the first stage, the temperature reaches 230 K when the three-point attachment anchors are connected to a room-temperature load.
At the end of the MODIS instrument’s life, the Passive Radiative Cooler will provide a 3K margin to the 83K operating temperature for the cold Focal Planes.