Status: Completed
Category: Embedded Systems · Aerospace Systems Engineering · CubeSat Engineering · ADCS · Sensor Fusion · Control Systems · SDR · Digital Twin
Project Type: Aerospace Engineering Prototype
Successor Project: AkshaRaksha
Overview
Stellar Crest was a laboratory-scale CubeSat prototype built to study the core subsystems of a modern small satellite.
Instead of focusing only on stabilization, the project modeled a full satellite stack: attitude determination, attitude control, telemetry, command handling, ground software, SDR communication, and digital twin simulation.
It prioritized hands-on implementation, with each subsystem developed, tested, and integrated independently before being carried forward into AkshaRaksha.
What it established
A working engineering baseline for later mission-oriented satellite communication work.
Details
Objectives
- Design a modular CubeSat architecture.
- Develop a three-axis attitude determination system.
- Build a three-axis reaction wheel stabilization platform.
- Implement real-time sensor fusion.
- Develop a cascaded PID-based attitude controller.
- Create a digital twin for visualization and controller validation.
- Design a telemetry and command architecture.
- Build a custom ground station.
- Explore software-defined radio communication.
- Validate subsystem interaction through real-time experiments.
- Hardware and software must be designed together in embedded aerospace systems.
- Mechanical balance significantly affects controller performance.
- Sensor fusion greatly improves orientation estimation accuracy.
- Digital twins simplify debugging and testing.
- Reliable telemetry is essential for understanding system behaviour.
- Modular software architecture improves maintainability and scalability.
- Real-time systems require careful timing and deterministic execution.
Engineering Domains
Embedded Systems · Aerospace Systems Engineering · CubeSat Engineering · Attitude Determination Systems · Attitude Control Systems · Sensor Fusion · Control Systems · Real-Time Embedded Programming · Telemetry Systems · Ground Station Development · Software Defined Radio · Digital Twin Simulation · Robotics
System Architecture
Subsystems
Flight computer
Hardware: ESP32
Responsibilities: Acquire sensor data · Execute sensor fusion algorithms · Run attitude control algorithms · Generate telemetry packets · Receive and process commands · Control reaction wheel motors · Perform system diagnostics · Record system events
Attitude determination system
Purpose: Estimate the orientation of the spacecraft in real time.
Sensors: MPU6050 — three-axis accelerometer and three-axis gyroscope
Sampling Rate: 50 Hz
Outputs: Roll · Pitch · Yaw
Sensor Fusion: A complementary filter combines gyroscope and accelerometer measurements to produce stable and computationally efficient orientation estimates. The filter compensates for gyroscope drift and accelerometer noise, producing reliable Euler angle estimates suitable for embedded real-time systems.
Attitude Representation: Euler angles (Roll, Pitch, Yaw), continuously updated and transmitted to the ground station.
Attitude control system
Purpose: Maintain the desired spacecraft orientation using closed-loop control.
Control Strategy: Cascaded PID controller
The cascaded architecture provides improved stability, smoother response, and better disturbance rejection compared to a single-loop controller.
Reaction wheel assembly
Three independent reaction wheels — one per rotational axis. The wheels generate control torque by conserving angular momentum, allowing the spacecraft to rotate without external forces.
Objectives: Stabilize spacecraft orientation · Correct attitude errors · Demonstrate spacecraft rotational dynamics · Validate closed-loop control algorithms
Supporting Systems
Firmware and telemetry
The embedded firmware is modular and deterministic. It reads the IMU, estimates attitude, runs the controller, drives the reaction wheels, and generates telemetry.
Includes: sensor drivers · sensor fusion · PID control · command handling · diagnostics
Ground software
The digital twin and ground station provide visualization, telemetry replay, PID tuning, logging, and system monitoring.
Includes: orientation display · status monitoring · controller tuning · event logs
Communications
SDR experimentation and telemetry workflows were used to simulate satellite communication behavior and improve resilience concepts.
Includes: signal generation · packet encoding · modulation · demodulation · frequency hopping
Takeaways
Stellar Crest made the interactions between sensing, control, communications, and ground software concrete, and exposed the timing and integration issues that matter in real spacecraft systems.
Lessons Learned
Technologies Used
Hardware: ESP32 · MPU6050 · Reaction wheel assemblies · Motor drivers · ADALM Pluto SDR
Software: C · C++ · Python · GNU Radio · Custom Ground Station Software · Digital Twin Software
Engineering Concepts: CubeSat Engineering · ADCS · Sensor Fusion · Complementary Filter · Cascaded PID Control · Reaction Wheel Dynamics · Software Defined Radio · CPFSK Modulation · Frequency Hopping · Embedded Systems · Real-Time Systems · Telemetry Systems
Relationship to AkshaRaksha
Stellar Crest is the direct predecessor of AkshaRaksha. It served as the R&D platform where the core aerospace technologies, communication methods, and software architecture were validated before being expanded into a mission-focused system.
Technologies Carried Forward to AkshaRaksha:
Embedded flight computer architecture · Real-time firmware design · Telemetry packet architecture · Ground station software · Digital twin concepts · SDR communication · GNU Radio processing pipeline · CPFSK communication experiments · Frequency hopping concepts · Modular subsystem architecture · Systems engineering methodology · Hardware-software co-design principles · Mission planning workflow