ARC SENTINEL

Autonomous Remote CubeSAT - Sentinel Platform v1.0

System Architecture

ARC SENTINEL (Flight Computer) <---- LoRa 433 MHz ----> Ground Station

Flight Computer stack:
- ESP32 flight computer
- MPU6050 IMU
- DHT11 sensor
- LoRa SX1276
- ESP32-CAM over UART

Ground stack:
- Arduino/ESP32 + LoRa receiver
- USB serial to PC
- ground_station_bridge.py (WebSocket :8765)
- Next.js dashboard (:3000)

OTA uplink path:
PC -> Ground Receiver (USB) -> LoRa RF -> Flight Computer -> FC or CAM

Downlink flow:

1. Flight computer reads sensors every 2 seconds and transmits JSON over LoRa.
2. Ground receiver injects RSSI/SNR and forwards via USB serial.
3. Python bridge detects packet loss and broadcasts to WebSocket clients.
4. Next.js dashboard renders telemetry panels in real time.

Wiring - Flight Computer

LoRa SX1276 / Ra-02:

• VCC -> 3.3V
• GND -> GND
• SCK -> GPIO 18
• MISO -> GPIO 19
• MOSI -> GPIO 23
• NSS -> GPIO 5 (CS)
• RST -> GPIO 14
• DIO0 -> GPIO 2

MPU6050:

• VCC -> 3.3V
• GND -> GND
• SDA -> GPIO 21
• SCL -> GPIO 22

DHT11:

• VCC -> 3.3V
• GND -> GND
• DATA -> GPIO 4 with 10k pull-up to 3.3V

ESP32-CAM via UART:

• 5V -> 5V
• GND -> GND
• TX -> GPIO 16 (ESP32 RX2)
• RX -> GPIO 17 (ESP32 TX2)

Wiring - Ground Receiver

Use a second LoRa SX1276 with an Arduino/ESP32 connected to your PC:

• VCC -> 3.3V
• GND -> GND
• SCK -> GPIO 18
• MISO -> GPIO 19
• MOSI -> GPIO 23
• NSS -> GPIO 5
• RST -> GPIO 14
• DIO0 -> GPIO 2

Ground receiver firmware injects rssi_gs and snr into each packet before forwarding at 115200 baud.

Core Firmware Files

• firmware/flight_computer_ota/flight_computer_ota.ino
• firmware/esp32cam_ota/esp32cam_ota.ino
• firmware/lora_ground_receiver/lora_ground_receiver.ino
• ground-station/ground_station_bridge.py
• tools/arc_uplink.py

Key flight firmware constants:

#define LORA_FREQ          433E6
#define TELEMETRY_INTERVAL 2000
#define OTA_CHUNK_SIZE     128
#define APP_VERSION        "1.0.0"
#define SATELLITE_ID       "ARC-SENTINEL-01"

Increment APP_VERSION before OTA updates to verify remote flash success in telemetry.

ESP32-CAM Commands

Ground Bridge

Install and run:

pip install pyserial websockets
 
python ground_station_bridge.py --port /dev/ttyUSB0
python ground_station_bridge.py --port COM3

Bridge responsibilities:

• Parse serial telemetry JSON
• Detect sequence gaps and packet loss
• Broadcast over WebSocket :8765
• Forward UI uplink commands back to serial

Ground Station UI

cd ground-station
npm install
npm run dev

Open http://localhost:3000.

If the bridge is offline, demo mode starts after about 4 seconds.

OTA Uplink Tool

pip install pyserial tqdm
 
python arc_uplink.py ping
python arc_uplink.py status
python arc_uplink.py flash-fc  firmware/flight_computer_ota/flight_computer_ota.ino
python arc_uplink.py flash-cam firmware/esp32cam_ota/esp32cam_ota.ino
python arc_uplink.py flash-bin my_firmware.bin FC
python arc_uplink.py set interval 5000
python arc_uplink.py abort

Set SERIAL_PORT in arc_uplink.py to your ground receiver USB port.

LoRa Radio Configuration

Both radios must match exactly.

Telemetry Packet Format

{
	"id": "ARC-SENTINEL-01",
	"pkt": 42,
	"t": 84.0,
	"ver": "1.0.0",
	"accel": { "x": 0.010, "y": 0.050, "z": 0.980 },
	"gyro": { "x": 1.23, "y": -0.45, "z": 0.78 },
	"roll": 3.2,
	"pitch": -1.1,
	"mpu_temp": 27.4,
	"env": { "temp": 22.5, "hum": 55.0, "hi": 24.1 },
	"rssi": -72,
	"rssi_gs": -75,
	"snr": 8.5
}

Setup Summary

1. Install ESP32 board support in Arduino IDE.
2. Install libraries: LoRa, MPU6050, DHT, ArduinoJson, Base64.
3. Set partition scheme: Minimal SPIFFS (1.9MB APP with OTA).
4. Flash flight_computer_ota, esp32cam_ota, and lora_ground_receiver once over USB.
5. Install Python tools: pyserial, tqdm, websockets.
6. Run bridge and dashboard, then perform OTA via arc_uplink.py.

License

MIT License.

ARC SENTINEL v1.0 - 433 MHz - SF10 - BW125 - CR4/5 - OTA enabled.