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COBE Engineering Information
from the Cryogenics & Fluids Branch NASA Goddard Space Flight Center. |
The cooling on COBE was provided by liquid helium. The liquid helium was loaded before launch. During the mission, the liquid was slowly evaporated by the heat loads on the satellite, especially the radiant heat load from sunlight. In the diagram below, this radiant heat is shown as large arrows, arriving first at the dewar main shell (outer shell) on the right hand side of the diagram. Smaller arrows show how the radiant heat made its way into the system, with some heat reaching the liquid helium tank at the far left side of the diagram.
As the liquid evaporated, the resulting cold helium vapor flowed through the vent line and was vented to space. As it moved through the vent line, the cold vapor cooled the line, which in turn cooled the thermal shields that it was fastened to. These temperature shields helped reduce the amount of heat that reached the liquid helium tank. Blankets of multi-layer insulation, placed around the thermal shields, also helped reduce the heat load on the liquid helium.
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