SmallSat Avionics Subsystem with Integrated >1Gpbs Downlink
The avionics subsystem implements many critical functions. The risk tolerance is low because the subsystem is not allowed to fail. For this reason, a fully redundant system in mesh configuration is presented in this section. A mesh topology connects each slot directly to every other slot without the use of a centralized Switch slot, although in some cases the Switch can be embedded in the Payload modules.
As shown in Figure 8, each component in the subsystem has its own redundancy with full cross-strapping connecting all the components and redundancies. In a full mesh, the failure of one module does not affect the ability of any working module to communicate with any other module in the network.
As shown in Figure 8, each component in the subsystem has its own redundancy with full cross-strapping connecting all the components and redundancies. In a full mesh, the failure of one module does not affect the ability of any working module to communicate with any other module in the network.
Figure 1: Fully Redundant Avionics Subsystem with Mesh Topology Backplane
In the above figure, TT&C refers to the Telemetry, Tracking and Command interface, usually a low bandwidth radio to ground. Also, a high-speed downlink is proposed as part of the solution to manage the payload data, implemented with the RF-subsystem, gimbals, DAC FMC, and a baseband Modulator (MOD) implemented in a DSP board. In this system designed for small satellites, the functionalities of both C&DH and Attitude Determination and Control System (ADCS) are combined in a single SpaceVPX module to reduce SWaP. The telemetry data generated in the SpaceVPX subsystem and the data received from external payloads are stored in the FMC MM. This information is downloaded to ground through the High-Data Rate Downlink when the ground station is in range. The IO Slot is a board with internal redundancy (int red) added to support sensors/actuators that lack redundant interfaces and need support glue logic. The subsystem has no credible single points of failure. The spare modules can be powered on and off as needed and work in cold or hot backup configuration and the Data and Control Planes are dual-redundant (point-to-point cross-strapped).