The Surface Operations Module is the part of Asterius that lands on Europa. The SOM has two functions: to house the scientific payload, and to carry the WISP safely to the surface for deployment.
The SOM carries many instruments: a dust detector, energetic particle detector, and gas chromatographer for the atmosphere; acoustic measuring equipment, a multispectral imager (EuropaCam), and seismic accelerometers for the crust. It houses the antennas and the electronics, including the on-board computer. The Dynamic Isotope Power Source (DIPS) is mounted on the SOM, as are the attitude thrusters. Finally, the SOM holds the engines and fuel needed for a soft landing.