A Spacecraft Interface Card with Flexible Architecture for Multi-Mission Applications

This paper describes the design and key test results of the Spacecraft Interface (SCIF) Card, with a 6U form factor, to be used on NASA’s New Frontiers Dragonfly mission to Titan. The SCIF card has a flexible architecture to facilitate use across a variety of spacecrafts and incorporates a reprogrammable RTG4 FPGA to define information flow and interface protocols. An on-board soft-processor pulls data from interface control modules in the FPGA, stores the collected data into memory devices, and notifies that data is available to be read via interrupts. The SCIF has five primary responsibilities. First, it holds two copies of main flight software with 16MB of non-volatile MRAM storage and loads the software to a separate Single Board Computer (SBC) via a 32-bit cPCI bus interface. Second, it collects and monitors data from power, telecommunication, guidance/navigation/control (GNC), thermal subsystem components, cruise stage components, and science payloads via SpaceWire, UARTs (LVDS and RS-422), and analog interfaces. Data collected from these spacecraft elements is stored in either 8GB of NAND Flash or 16MB of SRAM. Dedicated communication links to other avionics cards internal to the Integrated Electronics Module (IEM) box is via UARTs and I2C links that supplement the cPCI bus. The FPGA also allows interfaces to be enabled or disabled for different phases of the mission to minimize power dissipation. Third, it monitors analog and discrete telemetry within the IEM box. Fourth, it manages timekeeping information for the IEM box by accepting a virtual pulse per second (PPS) and distributes timing synchronization within and external to the IEM. Fifth, the SCIF FPGA supports a Hardware Command Decoder (HCD) to parse information received from a Radio and executes uplink or downlink commands without main fight software intervening. The design and test status of the first two revisions of the card, the breadboard and the Engineering Model (EM), is reported below.