Engineers integrate the avionics vault mass simulator for the Europa Clipper avionics module to the top of the propulsion module in a cleanroom at the Johns Hopkins Applied Physics Laboratory (APL) in Laurel, Maryland. The mass simulator will be used as the stand-in flight mounting interface for the RF module upper antenna cluster and waveguide as well as solar array struts while the propulsion and RF modules are at APL. Once integration and testing are complete, the mass simulator will be removed and shipped back to NASA’s Jet Propulsion Laboratory in Pasadena, California.