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. **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 **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. **Benefits And Perks** 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 cover…