Senior GNC Engineer; Navigation

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.

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.

• 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

• 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 3
  
  DOF and 6
  
  DOF 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

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.

All full‑time employees are granted meaningful long‑term equity, sharing in the company's significant growth trajectory. We offer four (4) weeks of paid time off, ten (10) company‑paid holidays, and comprehensive health benefits – including 100% employee‑covered medical and strong dependent coverage, along with dental and vision plans. We also provide paid parental leave to support growing families, a $100 monthly fitness stipend to promote health and performance, and onsite EV charging for convenience.

In addition, employees enjoy perks like catered…