Ground‐Based Validation of Hera's Spacecraft Monitoring Camera

Abstract Hera is an ESA contribution to the international planetary defense effort. It is a deep‐space mission to the binary asteroid system Didymos and Dimorphos, designed to investigate the effects of NASA's Double Asteroid Redirection Test (DART), demonstrate autonomous navigation, and support close‐proximity investigation by two CubeSats. Hera includes a Spacecraft Monitoring Camera (SMC) for situational awareness during critical operations such as CubeSat deployments. Although not a science instrument, the SMC may also provide scientifically useful and outreach imagery. Integration was challenging because the SMC uses a private Packet Utilisation Standard (PUS) Type 210 service, was not modeled in the Hera spacecraft simulator, and was initially unsupported by the spacecraft Central Software (CSW). To enable early testing, a ground toolchain was developed for command generation, telemetry extraction, image reassembly, and PNG conversion. Without direct onboard support, commands and telemetry were encapsulated in PUS Service 2 packets, enabling test‐bench integration. Synthetic telemetry was used to validate the processing chain before restricted hardware access. Bench testing revealed a SpaceWire flow‐control anomaly that could stall the affected communication path, so planned SMC imaging during Hera's March 2025 Mars gravity‐assist flyby was canceled. The issue was subsequently addressed in a later flight‐software version, with cruise‐phase validation planned before asteroid proximity operations. This case shows how low‐level ground access, synthetic data, and staged testing can reduce the risk of deferring non‐launch‐critical onboard functionality until after launch.