Implementation of payload data handling unit on Korea pathfinder lunar orbiter

We designed and implemented a payload data handling unit (PDHU) for the Korean first lunar orbiter. The PDHU is an electrical unit to receive data transferred from one on-board computer and six payloads, store it into its own 64 Gbit mass storage, and transmit stored data to the ground station through an X-band transmitter. To meet requirements from missions of the orbiter, we firstly sketched a conceptual design of the PDHU, then we gradually improved our design. After the design phase, to realize and verify the design, we implemented an engineering model (EM) of the PDHU in advance. With an EM, we performed pre-interoperability tests across payload EM-equivalents and fixed some issues. Finally, we implemented the engineering qualification model (EQM), and then performed environmental tests. Now we are ready to test its functions on the electrical testbed (ETB). After the ETB test, we will implement a flight model (FM), then integrate it into the spacecraft.