# Robust and Reconfigurable On-Board Processing for a Hyperspectral Imaging Small Satellite
## 3 On-Board Processing Unit Design
### Hardware Design  
The OPU consists of a PicoZed System-on-Module (SoM), see Figure 0(a), and an in-house designed carrier Printed Circuit Board (PCB) referred to as the Break-out Board (BoB), see Figure 0(b). The PicoZed contains the Zynq XC7Z030-1 System-on-Chip (SoC) that has dual 667 MHz ARM Cortex-A9 cores and a Kintex-7 FPGA. The A9 cores of the SoC also feature the ARM NEON Single-Instruction-Multiple-Data (SIMD) extensions that are used to accelerate binning, see Section 3.4.1. The PicoZed was chosen due to flight heritage of the Zynq 7000 architecture [21; 62; 63] and because it features an FPGA which can be used to accelerate the heavy image processing tasks with sufficient performance to satisfy low latency requirements. Peripheral components of note are indicated in Figures 0(a) and 0(b). The BoB serves as an interstage between the electrical contact pins of the PicoZed and the wire harness interface to the satellite bus. It features an additional 8 GB SD-Card and has connectors for data and power interfaces shown in Figures 0(b) and 0(b). The OPU fully assembled can be seen in Figure 0(a) in the middle right, between two aluminum panels. The Hyperspectal Imaging (HSI) camera utilizes the monochrome version of the Sony IMX249 camera sensor inside the COTS camera module UI-5261 SE Rev. 4 from IDS Imaging Development Systems GmbH [64]. It has a pixel array that is 1936 pixels wide by 1216 \begin{table}
\begin{tabular}{c c} \hline \hline
**Design Principle** & **Short Description** \\ \hline Integrity & Ability to detect faults \\ Redundancy & Presence of backups \\ Locality & Physical separation of backups \\ Modularity & System consisting of independent components \\ Extensibility & Ability to add additional functionality \\ Configurability & Adjust functionality to user’s needs \\ Low latency & Fast processing for fast available data \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Overview of the guiding principles during the design and implementation of the OPU. pixels high. When integrated with the optical components, the camera forms a transmission grating push broom camera where light is dispersed along the width of the pixel array and the sensor height corresponds to the spatial, along-slit dimension. The Sony IMX249 sensor features 12-bit sample depth and the camera module has a maximum frame rate of 47 fps at 8-bit and 23 fps at 12-bit over its Ethernet interface that has a rated transfer speed of up to 1 Gbit/s [64]. The camera features electrical Input/Output (I/O) pins for capture triggering and flash signaling. The capture trigger pin is not used. The camera manufacturer provides a driver and C Application Programming Interface (API) for recording data. The payload is integrated into a COTS satellite bus. Notable satellite bus subsystems are the Attitude Determination and Control System (ADCS), the Electronic Power System  
Figure 1: Images of the PicoZed SoM (**a**) and the BoB (**b**). Connectors for mounting the two together are on the other side not shown here. Components in Figure 2 indicated. Figure 3: Images of HYPSO-1 during assembly, integration and testing. (**a**) Payload components. (**b**) Full satellite without panels. (**c**) Full satellite assembled. Figure 2: Overview of the most important hardware components in the payload and on the satellite bus and their interfaces. This figure shows a simplified payload-centric view to the left, and a simplified satellite-bus-centric view to the right. (EPS), the Flight Computer (FC) and the Payload Controller (PC), and the S-band radio. The ADCS subsystem, which is configured via the FC, controls the orientation of the satellite. The Pulse per second (PPS) from the Global Navigational Satellite System (GNSS) receiver in the ADCS is used for precise time synchronization. Main data, telemetry and command communication with ground stations are done via the S-band radio. Both the FC and the PC contain script engines to schedule actions outside of ground station contact.