ADCS team update

The Attitude Determination and Control System (ADCS) team is a group of Student Satellite members dedicated to determining the satellite’s orientation and controlling it based on mission requirements.

Over the past year, the ADCS team has focused on two major goals:

1. Developing a simulation environment to model the satellite’s motion accurately.
2. Building the hardware test setup, including both the controller board (mainboard) and the necessary test equipment.

To develop and validate the ADCS software, we need an accurate model of the satellite’s kinematics and dynamics. This tells you how the satellite responds to different torques. With this model and some heavy-duty math, it is possible to control the satellite’s orientation in space precisely.

For the SUTS mission, a major challenge comes from the Optical Communication (OCOM) payload, which demands accurate pointing to maintain a laser link with a ground station on Earth. Even the slightest misalignment could disrupt the connection.

So far, the team has successfully implemented two key modes:

• Detumbling – after the satellite is detached from the deployer into orbit, it tends to spin uncontrollably. The detumbling algorithm uses onboard electromagnets and the Earth’s magnetic field to de-spin – slow and stabilise – the satellite. It is much like a compass needle aligning with the magnetic field.
• Nadir pointing – this mode ensures the satellite consistently points toward the Earth’s surface, which is essential for establishing a communication link with our own ground station.

While we can’t test everything on Earth, it is possible to use a method called hardware-in-the-loop (HIL) simulation. This setup “tricks” the mainboard into thinking it’s in space, and then we observe how it responds. If the satellite behaves as expected, we can have confidence in our control algorithms. To pull this off, we need special equipment, along with sensors and the controller.

Our near-term goal is to validate the detumbling algorithm using HIL testing by the end of the year.

Looking ahead to next month, the team will focus on:

• Adding realistic noise and disturbances to the simulation to make it more accurate.
• Testing sensor accuracy and selecting the most reliable ones for flight.

There’s a lot more going on in the simulation development front — but we’ll save that for the next update.