The design of the Pleiades spacecraft employs a variation of the AstroSat platform, namely AstroSat-1000 of EADS Astrium SAS. The main design drivers for the S/C architecture were "satellite pointing agility and image location accuracy." Agility requires a very compact S/C design; hence, the imaging instrument is integrated inside the bus. A high degree of image location accuracy is achieved by minimizing the interface between the imager and the bus. The bus structure is of hexagonal shape, with three solar arrays positioned at 120º at the top of the platform (fixed mounting of solar arrays), and three star trackers in a quasi tetrahedron configuration, optimizing the attitude determination accuracy. The solar array size is minimized by using high-efficiency triple-junction cells. The satellite electrical architecture is organized around a central computer, based on a SPARC ERC 32 computer, communicating via MIL-STD-1553B buses to the onboard equipment. The computing, monitoring and reconfiguration functions are centralized in the OBMU (On Board Management Unit). The IMU (Instrument Management Unit) gathers the instrument interfaces: instrument thermal control hardware, mechanisms command, detection unit power conversion. All the other instruments have their own 1553 interface and directly interface with the OBMU. Two 1553 buses are nominally used: the first one for cyclic tasks, mainly allocated to AOCS and thermal control., the second one dedicated to burst exchanges, mainly payload instruments.