In-situ measurements on the surface of planets, comets or asteroids are very interesting from the scientific point of view (see Mars-96 mission or the ESA Rosetta mission). But it is very difficult to realize a reliable lander under hard cost constraints. One problem consists in the control of the operations of a complex of instruments. A conventional way to do this is the connection of different instruments via standard bus. The proposed system design is characterized by the separation of the instrument electronics in sensor specific front-end electronics close to the sensor and a more general electronic part. The strong limited resources of the lander and the limited instruments require a reliable system architecture by a minimum of hardware. For this reason a centralized system architecture is selected with a redundant processor structure. This combines the advantages of a high reliable central processor and the non-sensitivity of the system on interface failures. The paper describes few imaging experiments on a cometary lander as an case study and appropriate architectures for a centralized command and data handling system. One chapter describes the system implementation, especially the use of the advanced microelectronics packaging technologies for a high-density micro-electronics. The electronic circuitries can be arranged together with the necessary instrument interfaces on a single multi-chip module.