Payload

Oregon State University (OSU) AIAA OSUSat/SCRT Climate Science CubeSat

Welcome to the central repository for the OSUSat Climate Science CubeSat project. This repository contains the hardware designs, firmware, and documentation for the sub-systems comprising the satellite.

Mission Context & Goals

The OSUSat Climate Science CubeSat is a low-Earth orbit (LEO) satellite designed to capture high-resolution imagery and scientific data for climate science research.

Mission Objectives

1. Earth Observations: Capture multispectral or high-resolution imagery using a dual-camera payload to study surface health, atmospheric conditions, cloud formations.
2. Reliable Power Delivery (EPS): Harvest solar power from 6 body-mounted solar panels, manage charge for 4x 18650 Li-ion batteries, and distribute and regulate power rails to prevent overcurrent/overvoltage events.
3. Command & Telemetry (OBC): Orchestrate system operations, manage communication buses (CANBus, UART, I2C, SPI), process ground commands, and monitor satellite health.

System Architecture

The satellite is divided into five primary subsystems interconnected via a shared backplane connector (exposing power rails and UART/CAN control buses):

graph TD
    Solar[Solar Panels & Batteries] --> EPS[Electrical Power System - EPS]

    EPS -->|Power| OBC[On-Board Computer - OBC]
    EPS -->|Power| Payload[Science Camera Payload]
    EPS -->|Power| ADCS[Attitude Determination & Control - ADCS]
    EPS -->|Power| Comms[UHF Communications]

    OBC <-->|Control Bus| EPS
    OBC <-->|Control Bus| Payload
    OBC <-->|Control Bus| ADCS
    OBC <-->|Control Bus| Comms

    Comms <-->|Radio Link| Ground[Ground Station]

1. Electrical Power System (EPS)

• Microcontroller: NXP S32K3 Series / STM32L496xx (ARM Cortex-M4)
• Responsibilities:
  • Solar energy harvesting with Maximum Power Point Tracking (MPPT).
  • Battery charge/discharge management (2 independent packs of 2x 18650 cells).
  • Voltage regulation (3.3V & 5V rails) with software-controllable load switches.
  • Fast hardware-level and software-level overcurrent protection.
  • Hardware watchdog monitoring.
  • Broad mission context management using the MCU

2. On-Board Computer (OBC)

• Microcontroller: Main MCU + STM32H743xx (ARM Cortex-M7)
• Responsibilities:
  • Master command parsing and state management.
  • Health heartbeats and telemetry collection.
  • Orbital calculations and scheduling payload imaging windows.
  • Ground station radio communication interface.

3. Payload

• Processor: Raspberry Pi Compute Module 4 (CM4)
• Responsibilities:
  • High-speed dual-camera scientific imaging.
  • Actuator/motor driver control (e.g., lens shutters, filter wheels) (V1 Only).
  • Image compression and storage before downlink.

4. Attitude Determination and Control System (ADCS)

• Responsibilities: Detumbling the spacecraft, aligning the imaging payload to nadir pointing, and tracking target orientations.

5. UHF Communications (Comms)

• Responsibilities: Uplinking commands and telemetry requests from ground stations, and downlinking collected science data and telemetry beacons.

Repository Structure

The project uses a versioned directory structure separating hardware and firmware iterations:

.
├── .github/                     # GitHub Workflows & Issue/PR Templates
│   └── workflows/
│       ├── build_and_docs.yml   # CI/CD action defining the pipeline
│       └── build_and_test.sh    # Dynamic build script runner
│
├── adcs/                        # Attitude Determination and Control System
│   ├── v1/
│   └── v2/
│
├── eps/                         # Electrical Power System Subsystem
│   ├── v1/                      # Version 1 (Prototype Model)
│   │   ├── firmware/            # STM32L4 firmware (CMake, CUnit tests, mocks)
│   │   ├── hardware/            # KiCad schematic, layout, symbols, & footprints
│   │   └── documentation/       # Doxygen, Sphinx configuration & spec files
│   ├── v2/                      # Version 2 (Placeholder for v2 development)
│   └── documentation/           # Bootflows, subsystem specifications, & kickoff info
│
├── obc/                         # On-Board Computer Subsystem
│   ├── v1/                      # Version 1 (Prototype Model)
│   │   ├── firmware/            # STM32H7 firmware (CMake)
│   │   ├── hardware/            # KiCad schematic and layout
│   │   └── tests/               # Pico-based LoRa packet transmission test
│   ├── v2/                      # Version 2 (Placeholder for v2 development)

Getting Started & Building

1. Prerequisite Toolchains

Ensure you have the following installed on your host system:

• ARM Cross Compiler: gcc-arm-none-eabi
• Build System Tools: cmake, make, g++
• Documentation Generators: doxygen, Python 3 + sphinx

2. Fetching Submodules

This repository utilizes submodules (such as osusat/core and osusat/messaging). Clone with submodules or initialize them:

git submodule update --init --recursive

3. Hardware Development & KiCad Templates

To create new expansion / daughterboard hardware designs in KiCad, symlink the shared template directory to your local KiCad user template path:

• Linux:

  mkdir -p ~/.local/share/kicad/10.0/template
  ln -sf /path/to/cubesat/repo/shared/kicad/templates/test_board ~/.local/share/kicad/10.0/template/test_board

• Windows (PowerShell):

  New-Item -ItemType Directory -Force -Path "$env:APPDATA\kicad\10.0\template"
  New-Item -ItemType SymbolicLink -Path "$env:APPDATA\kicad\10.0\template\test_board" -Target "C:\path\to\cubesat\repo\shared\kicad\templates\test_board"

Once symlinked, open KiCad, click File → New Project from Template..., select the User Templates tab, and choose OSUSat Backplane Test Board Template.

For full manual setup options and details, see shared/kicad/README.md.

4. Compilation Guide

Building for the ARM Target (e.g., EPS v1)

To build the firmware binaries to flash onto the MCU:

cd eps/v1/firmware
cmake -B build_arm -S . -DCMAKE_TOOLCHAIN_FILE=arm-none-eabi-toolchain.cmake
cmake --build build_arm

Outputs: .elf, .hex, and .bin files will be generated under build_arm/.

Building Host Tests / Hardware-in-the-Loop (HITL) Mocks

To build and execute unit tests on your local machine:

cd eps/v1/firmware
cmake -B build_hitl -S . -DTARGET_ARCH=HOST -DBUILD_HITL=ON
cmake --build build_hitl
cd build_hitl && ctest --output-on-failure

CI/CD Pipeline

The repository uses a generalized GitHub Actions workflow:

• Scope-Based Execution: Uses git diffs to detect which subsystem version has been modified (e.g. eps/v1/ vs obc/v1/) and builds only the affected firmware.
• Continuous Integration: Runs host-based CTests automatically to verify changes.
• Documentation Deployments: Generates Doxygen API listings and Sphinx documentation on successful builds. Pull Requests automatically receive a comment with links to Pages-hosted previews of the documentation.

Quality Assurance & Contributions

Before submitting a Pull Request, contributors must follow the project's QA procedures found in /documentation:

1. Issue Checkout: Before work or contributions begin, ensure your changes are encapsulated by an issue in the GitHub project
2. Design Guidelines: For any and all changes, follow the design guidelines.
3. Design Reviews: Complete the Schematic Review Checklist and Layout Review Checklist checklists before fabricating PCBs.
4. Firmware Guidelines: Adhere to the HITL Guidelines and Keeping the HAL Policy Free design rules.
5. Acceptance Tests: All hardware deliverables require a formal ATP (Acceptance Test Procedure).