To demonstrate that the science objectives of EJSM-Laplace can be achieved, a model payload of 11 instruments has been studied for each of the two spacecraft, the Jupiter Ganymede Orbiter (JGO) and the Jupiter Europa Orbiter (JEO).

The model payload instruments were identified by the Joint ESA-NASA Science Definition Team (JSDT). While notional, the two model payloads are used to bind the engineering aspects of the EJSM-Laplace mission design, spacecraft, and operational scenarios, and to demonstrate achievability of the mission goals. The industrial studies included also optimization of the accommodation for the payloads.

The tables below present the model payloads for JGO and JEO, their primary science contribution and key characteristics. Several model payload instruments on both spacecraft are fundamentally similar but with instrument parameters adjusted according to their primary targets: Ganymede in the case of JGO and Europa for JEO. The other instruments are complementary to best address the exploration of the Jupiter system as a whole. Several options were investigated to see how to most efficiently distribute the instrumentation between the two spacecraft. The instruments were evaluated on the basis of their ability to meet the measurement objectives, perform in the radiation environment, and be designed to meet planetary protection requirements. The flight payload, on both JGO and JEO, will be selected following two coordinated Announcements of Opportunity, one to be released by ESA for JGO and one to be released by NASA for JEO.

The estimated mass of the model payload without radiation shielding is 104 kg for JGO and 106 kg for JEO. These mass estimates account for projected modifications necessary to perform in the radiation environment. Mass for shielding is estimated separately and accounted for at system level.