Function:
The side panels on ACE provide a home for the electronics and other systems that keep ACE running. These systems include:
The side panels also provide a housing for the propulsion system, which can be seen in two dimentions on the -Z panels which group 1 has assembled, and in the diagram to the right, an "exploded" view of ACE.
Two instruments, CRIS and SWIMS, are attached to the side panels. They were placed on the side panels so that they could have the correct point of view towards the sun, as well as to conserve space on the crowded +Z (upper) deck.
On the real spacecraft, the side panels were actually slid into an octagonal framework (which you can see in the diagram), but that was somewhat impractical for this model.
Pictures:
You may click on each of the thumbnails (small images) for a larger picture.