The spacecraft's structure is divided into two modules. The first is a propulsion module, containing tanks, thrusters and associated plumbing. The other, the equipment module, is composed of an equipment deck, which supports engineering components and the radiation experiment, and a science deck connected by struts. The top side of the science deck supports the Thermal Emission Imaging System (THEMIS), Gamma Ray Spectrometer (GRS), the High-Energy Neutron Detector (HEND), the neutron spectrometer and the star cameras, while the underside supports engineering components and the GRS's central electronics box.
The structures subsystem weighs 81.7 kilograms (180.1 pounds).