The HERA satellite's Payload Data Handling Unit (PDHU) features a Mass Memory Unit that is adept at managing large volumes of data, essential for space missions. The unit boasts a write and read performance of up to 10 Mbps via SpaceWire connections, ensuring efficient data handling capabilities. It offers a substantial storage capacity of 486 Gbit (EOL), accommodating extensive data collection over time. The PDHU interfaces include three SpaceWire connections for payloads and a redundant (1N + 1R) interface for the onboard computer (OBC), emphasizing reliability in data transactions.