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, ownership, and excellence are decisive advantages - and we're building a world-class team to turn bold ideas into real capability. 

This is a rare opportunity to join at an early stage, where you'll have significant ownership, collaborate with exceptional teammates, and make a direct, measurable impact on our mission and the future of the company - regardless of your function.  

Senior GNC Engineer (Navigation)

We are seeking a Senior GNC Engineer to develop advanced navigation solutions for Castelion's long-range hypersonic strike vehicles. This role is critical to enabling precise state estimation across all mission phases, including GPS-denied environments. You will work hands-on with multidisciplinary engineering teams to design, analyze, implement, and validate multi-sensor navigation algorithms, including star tracker-based alternative navigation and sensor fusion architectures, in a fast-paced, hardware-driven environment.

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

Basic Qualifications

• 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

Castelion offers a generous benefits package. Please refer to the bottom of our Careers page for more details.  

Other Duties 

Please note this job description is not designed to cover or contain a comprehensive listing of activities, duties or responsibilities that are required of the employee for this job. Duties, responsibilities and activities may change at any time with or without notice. 

Additional Eligibility Requirements 

This position may require access to classified information or restricted U.S. Government sites, systems, or information, as determined by the Company and/or applicable U.S. Government requirements. If the position is so designated, your employment in the role may be contingent upon your ability to obtain and maintain the required U.S. Government security clearance or other government authorization, and to satisfy any citizenship or other eligibility requirements imposed by applicable law, regulation, executive order, or government contract requirements. You will be notified if and when such requirements apply. 

Affirmative Action/EEO Statement 

Castelion is an Equal Opportunity Employer. We are committed to providing equal employment opportunities to all applicants and employees without regard to race, color, religion, sex, sexual orientation, gender identity, national origin, age, disability, genetic information, protected veteran status, or any other characteristic protected by applicable federal, state, or local law. 

Castelion is committed to providing reasonable accommodations to qualified individuals with disabilities throughout the application and hiring process. If you require a reasonable accommodation to complete an application, participate in the interview process, or otherwise participate in the hiring process, please contact hr@castelion.com. Requests for accommodation will be considered on an individual basis and handled in accordance with applicable law. 

Castelion is committed to fostering a workplace where employment decisions are based on qualifications, business needs, and the ability to perform the essential functions of the role, with or without reasonable accommodation. 

EAR/ITAR Requirements 

This position requires access to export-controlled information, and as such, employment (or hiring of a contractor) is contingent upon the candidate’s ability to access all applicable export-controlled information without additional export licensing being required by the Bureau of Industry and Security and/or the Directorate of Defense Trade Controls.