Senior GNC Engineer (Navigation)

About the role

Why Castelion, Why Now Castelion is moving incredibly fast to develop and deliver advanced defense systems at a time when execution matters more than ever. We believe focus and technical excellence are decisive advantages - and we are building a team that can deliver real capability, not just concepts. This is a rare opportunity to join at an early stage, where your work will directly shape critical systems, influence major technical decisions, and have immediate, real-world impact.

Responsibilities

• Design and develop navigation algorithms for high-speed flight vehicles, including inertial navigation and alternative navigation (alt-nav) methods
• Develop and implement multi-sensor fusion architectures using Extended Kalman Filters (EKF) and related estimation techniques
• Integrate data from IMUs, star trackers, GNSS (when available), and other onboard sensors to provide robust, high-accuracy state estimation
• Work closely with avionics, flight sciences, and flight software teams to integrate navigation algorithms into real-time embedded systems
• Conduct modeling, simulation, and analysis to evaluate navigation performance, error growth, and robustness under GPS-denied and degraded conditions
• Support hardware-in-the-loop (HIL) testing, flight testing, and post-flight analysis, translating results into system-level improvements
• Characterize sensor performance, biases, and error sources to inform filter design and tuning
• Develop tools and frameworks for navigation algorithm development, verification, and validation
• Mentor junior engineers and contribute to best practices in navigation and estimation
• Partner closely with program leadership to make technical trades aligned with mission success

Requirements

• Bachelor's, Master's, or PhD in Aerospace Engineering, Electrical Engineering, or related field
• 5+ years of experience in navigation algorithm development, analysis, and validation for aerospace or high-performance dynamic systems
• Strong background in estimation theory, including Extended Kalman Filters (EKF) and multi-sensor fusion
• Experience with inertial navigation systems (INS) and integration with external aiding sources (e.g., GNSS, star trackers, or similar sensors)
• Familiarity with alternative navigation (alt-nav) techniques for GPS-denied environments
• Proficiency in modeling and simulation tools such as MATLAB/Simulink or equivalent
• Experience with 3DOF and 6DOF simulation environments and real-time implementation of navigation algorithms
• Strong understanding of sensor error modeling (IMUs, star trackers, etc.) and calibration techniques
• Familiarity with flight software integration and real-time embedded systems
• Strong problem-solving mindset, thriving in a fast-paced, hardware-rich, high flight cadence environment
• U.S. citizenship required
• Ability to obtain and maintain a U.S. government–issued security clearance required

Benefits

• Meaningful long-term equity for all full-time employees
• Four (4) weeks of paid time off
• Ten (10) company-paid holidays
• Comprehensive health benefits – including 100% employee-covered medical and strong dependent coverage, plus dental and vision plans
• Paid parental leave
• $100 monthly fitness stipend
• Onsite EV charging
• Catered meals
• Company-covered food during high-demand periods
• Fully stocked kitchen