GalaxEye Space GNC Engineer Interview: Rounds, Questions and Preparation

What the job involves

A GNC (Guidance, Navigation and Control) Engineer designs algorithms that determine a spacecraft's position and orientation, plan its path, and compute actuator commands to follow that path. In a space and defence tech company, you might work on satellite attitude determination, orbit control, interplanetary trajectory design, or missile guidance systems. Day to day involves MATLAB/Simulink or Python modelling, sensor fusion (star trackers, IMUs, GPS), control law tuning, and hardware-in-the-loop testing.

Role and Technical Knowledge

1. 1

   Explain the difference between guidance, navigation, and control in a satellite mission.

   Define guidance as trajectory planning, navigation as state estimation from sensors, and control as actuator commands. Give a concrete example like orbit raising or station-keeping.

2. 2

   How do you represent attitude in 3D space, and why are quaternions preferred over Euler angles?

   Mention rotation matrices, Euler angles, and quaternions. Highlight gimbal lock and computational efficiency as key advantages of quaternions.

3. 3

   What is a Kalman filter and how would you use it for satellite attitude estimation?

   Describe predict-update steps, process and measurement noise, and fusing star tracker and gyro data. Mention extended or unscented variants for nonlinear systems.

4. 4

   Describe the main orbital perturbations that affect a LEO satellite and how GNC compensates for them.

   Cover J2 effect, atmospheric drag, solar radiation pressure, and third-body effects. Explain how thrusters or reaction wheels are used for orbit and attitude control.

Practical Scenarios

1. 5

   Your satellite's attitude control system is oscillating. How do you diagnose and fix it?

   Check sensor noise, control gains, actuator saturation, and structural flexibility. Suggest reducing gain, adding a filter, or re-tuning with a model.

2. 6

   You need to design a controller for a CubeSat to point a camera at a ground target. Walk through your approach.

   Define pointing requirements, choose reaction wheels or magnetorquers, design a PID or LQR controller, simulate in Simulink, and test with hardware-in-the-loop.

3. 7

   How would you validate your GNC algorithms before launch?

   Mention model-in-the-loop, software-in-the-loop, processor-in-the-loop, and hardware-in-the-loop simulations. Include Monte Carlo runs for robustness.

4. 8

   A sensor fails during a mission. How does your GNC system detect and recover?

   Discuss fault detection via residual monitoring, redundancy management, and switching to a backup sensor or safe mode. Mention isolation and reconfiguration logic.

Behavioural and HR

1. 9

   Why do you want to work in space and defence tech, and why our company?

   Show genuine interest in the sector, mention specific missions or technologies, and align your skills with the company's focus like small satellites or remote sensing.

2. 10

   Describe a time you worked in a team to solve a complex engineering problem.

   Use STAR format: situation, task, action, result. Highlight your specific contribution, collaboration, and what you learned.

3. 11

   How do you handle tight deadlines when a simulation is not converging?

   Explain prioritisation, breaking the problem into smaller parts, seeking help, and communicating progress. Show resilience and a systematic approach.

4. 12

   Where do you see yourself in three years in this role?

   Express desire to deepen technical expertise in GNC, take ownership of subsystems, and contribute to successful missions. Avoid vague answers.

Domain Awareness and Current Trends

1. 13

   What are the key differences between GNC for launch vehicles versus satellites?

   Launch vehicle GNC focuses on ascent trajectory, staging, and aerodynamic forces; satellite GNC focuses on on-orbit attitude and orbit maintenance. Mention real-time constraints and fault tolerance.

2. 14

   How is AI or machine learning being used in GNC for space systems?

   Discuss adaptive control, fault detection, and autonomous navigation. Mention challenges like certification and limited flight heritage.

3. 15

   What is the role of GNC in autonomous rendezvous and docking?

   Cover relative navigation using lidar or cameras, trajectory planning for approach, and close-loop control for docking. Mention safety and abort scenarios.

4. 16

   What are the GNC challenges for small satellites compared to large ones?

   Highlight limited power, mass, and computing resources. Discuss simpler sensors, lower control authority, and the need for robust, low-complexity algorithms.