Test as you Fly: Using Flight Telemetry in the Mars 2020 Uplink Simulation & Validation Process

Abstract

Mars2020's approach to command load simulation & validation steered away from heritage design early on in Mission System development. Whereas previous missions used Sequence Generator (SeqGen) to validate their command load, Mars2020 chose to adapt software originally developed for Mars Science Laboratory (MSL), Surface Simulation (SSim), in order to meet new mission performance requirements. This decision meant a complete redesign of the surface mission uplink commanding validation architecture, but it also provided room for meaningful improvements. SSim is a Flight Software (FSW)-in-the-loop sequence and command simulator, enabling much faster than real-time execution. It was originally developed for MSL Rover Planners to simulate and validate their commanding of rover mobility, robotic arm, and sampling activities. For Mars2020, SSim has since been expanded to include the modeling of system-level functions such as power, telecommunications, and instruments. It affords the operations team the ability to simulate commanding in a very flight-like manner, a significant change from the heritage process involving the use of SeqGen. Using a FSW-in-the-loop simulator for uplink command validation provides several key advantages over heritage simulation tools. Because of the similarity between SSim and the rover FSW, the Mars2020 validation process is able to routinely incorporate the latest known state of the flight vehicle into the validation tools, ensuring that the simulation and validation initial condition used in uplink planning is the best possible representation of the onboard state. A set of new tools and new and improved processes developed for Mars2020 enable this usage of flight vehicle state in uplink planning, and by doing so, prevent divergence between spacecraft state tracked on the ground and the real state of the rover on Mars. The adoption of SSim for uplink command validation completely redesigned the surface validation process. The development of this design presented many novel challenges resulting in key decisions and trades that could not directly leverage heritage designs or experience. This study will discuss the formulation of, and key decisions involved in, the Mars2020 surface validation process architecture in hopes of serving as a blueprint for future missions.