Design of a High-Performance EGSE Architecture for the Dragonfly Mission to Titan

We present here the design of the high-performance, precisely-synchronized Electrical Ground Support Equipment (EGSE) architecture that is used to rigorously test the Integrated Electronics Module (IEM) of Dragonfly. Dragonfly is a NASA New Frontiers class mission that is expected to launch in 2028 to travel to Titan, the largest moon of Saturn, where it will analyze Titan's chemistry in multiple locations by autonomously flying from one location to another. The Dragonfly mission requires a complex IEM with interfaces to many different peripherals, several of which have relatively tight timing constraints to enable Dragonfly to fly. The EGSE design presented here enables the simultaneous and precisely coordinated simulation of these peripherals, which include Dragonfly's rotor-drive electronics, critical bus power electronics, navigation cameras, LIDAR sensor, inertial measurement units, and more. The EGSE for testing the Dragonfly IEM consists of custom embedded software running on the RTEMS real-time operating system (RTOS), which runs on the ARM processor of a Xilinx Zynq 7015 System-on-a-Chip (SoC). The Zynq SoC is part of the Avnet PicoZed, which sits atop a custom carrier card that breaks out the I/O of the Zynq to be able to connect to the desired interfaces on the IEM. This EGSE architecture is scalable, meaning that multiple PicoZeds can be used within the same EGSE system, with each PicoZed emulating different interfaces to the IEM. For example, one PicoZed may be responsible for emulating the LIDAR interface, while another PicoZed is responsible for emulating the high and medium gain antenna gimbal drive electronics interfaces. All PicoZeds are precisely synchronized using common timing signals, which when combined with the features of the RTEMS RTOS and the Zynq's programmable logic, enables very fine control of simulation timing. The EGSE design for testing the Dragonfly IEM is also capable of precisely timestamping events. Events, such as the rising edge of the stop bit of a packet received on a UART, are timestamped with 100ns resolution. Thousands of these timestamps are latched per second and sent to an upstream data collection system to be logged, enabling detailed characterization of the IEM's performance. The timestamps can also be directly compared across different PicoZeds within the same EGSE system, since the PicoZeds are all tightly synchronized to one another. The PicoZeds all interface via Ethernet to a central system, which manages the PicoZed collective and runs the top-level simulation. Command and telemetry for each PicoZed are defined using the open-source, declarative language Kaitai Struct. Packet handlers running on the ARM parse these command packets and then write data via AXI to the programmable logic portion of the Zynq, where the data is queued for the selected interface, sent through the first circuit protection that is built into the carrier cards, and received by the Dragonfly IEM.