Images

Power Distribution Unit Installed

The STEREO “A" observatory (the one that will be placed ahead of Earth in its orbit around the sun) shown after installation of its power distribution unit (PDU)—the black box with red cap near center of photo. The PDU, which is installed on both STEREO observatories, distributes power to all spacecraft systems. It also provides power to devices aboard each spacecraft used to separate the two observatories from each other after their launch into space, and deployment of both spacecraft's solar arrays.

Aside from the battery, the PDU is the largest electronics unit on each spacecraft. However, it's small enough to fill a backpack, and weighs approximately 30 pounds.

Credit: NASA/Johns Hopkins University Applied Physics Laboratory