Senior Satellite Guidance, Navigation, and Control (GNC) Engineer

About Portal Portal Space Systems is on a mission to expand humanity’s freedom of movement in space. We’re building the spacecraft that makes that mission possible. From our Bothell, WA headquarters, we design vehicles with the maneuverability, resilience, and adaptability needed for the next era of orbital operations. Every system we build is in service of a simple idea: space should be more accessible, responsive, and capable. Joining Portal means stepping into a team that believes in bold engineering, fast iteration, and the power of small groups to change what’s possible. If you want your work to directly shape the future of in-space mobility, join us. Position Summary We are hiring a Sr. GNC Engineer to lead the full lifecycle development of the GNC subsystem for flight software as a member of the Software, GNC, and Autonomy team. You will be the responsible engineer for the GNC subsystem, overseeing architecture, design, and development of the subsystem and associated modeling and simulation capabilities. You will be the technical leader, working with other subsystem owners to define a comprehensive set of functional and performance requirements, decomposing complex work, and providing guidance and mentorship to other GNC engineers. Core Responsibilities Design, develop, and validate GNC algorithms with a focus on precise pointing and stability control using linear control methods. Perform high-fidelity simulations, modeling, and analysis of guidance, navigation, and control systems. Lead GNC avionics integration efforts, including sensor calibration, hardware-in-the-loop testing, and software validation. Support mission planning, trajectory design, and optimization of spacecraft pointing performance. Collaborate with multidisciplinary teams, including software engineers, avionics specialists, propulsion engineers, and mission planners. Conduct system performance assessments, stability analysis, and develop risk mitigation strategies. Develop and document technical specifications, interface control documents, and system architecture designs. Provide hands-on support for integration and testing of GNC flight hardware and software. Collaborate with partner organizations on satellite development. Mentor junior GNC engineers. What You Bring To Portal Demonstrated experience leading full development lifecycle of GN&C subsystem in at least one aerospace program Demonstrated knowledge and experience with Rendezvous and Proximity Operations and Docking Demonstrated experience decomposing large/complex nebulous tasks into clearly defined subsets of work that can be done personally or delegated to other members of the team Ability to perform complex GNC system analyses of kinematics, dynamics, and control systems using existing and/or self-developed tools Advanced understanding of classical and modern control theory, system-level trade studies, architecture development, and systems integration & analysis Experience synthesizing and evaluating Monte Carlo simulations, hardware-in-the-loop, and software-in-the-loop testing Deep knowledge of astrodynamics, orbital mechanics, attitude kinematics and dynamics Experience with performing system safety analyses including Functional Hazard Assessments; Failure Modes, Effects and Criticality Analyses; and Fault Tree Analysis Basic Qualifications Bachelor's, Master’s, or PhD in Aerospace Engineering, Electrical Engineering, Mechanical Engineering, or a related field or equivalent. Minimum of 5 years of experience in spacecraft and satellite GNC development. Experience designing, implementing, and testing autonomous navigation, guidance and control with real-world robotic or aerospace systems, from simulation through field deployment. Preferred Qualifications Expertise in precise pointing control using linear control methods. Proficiency in MATLAB, Simulink, Python, or C/C++ for simulation and algorithm development. Experience with avionics integration, including working with IMUs, star trackers, sun sensors, magnetorquers, GPS receivers, and reaction wheels. Deep understanding of spacecraft dynamics, orbital mechanics, and trajectory optimization. Experience with high-fidelity simulation, hardware-in-the-loop (HIL), and software-in-the-loop (SIL) testing. Familiarity with aerospace industry standards and regulations. Strong problem-solving skills and ability to work in a fast-paced, collaborative environment Experience with real-time embedded software development and flight software implementation. Familiarity with Kalman filtering, guidance laws, and autonomous navigation techniques. Previous experience in mission operations and post-launch analysis. Knowledge of spacecraft communication protocols and fault detection systems. Hands-on experience with integration and test campaigns for space missions. Pay Range: $150,000 - $205,000 Compensation and Benefits: Your actual level and base salary will be determined on a case-by-case basis and may vary based on the following considerations: job-related knowledge and skills, education, and experience. At Portal, your base salary is just one part of your total rewards package. You may also be eligible for long-term incentives, in the form of company equity at an exciting time of company growth as well as potential bonuses. You will also receive access to comprehensive medical, vision, and dental coverage (premiums paid by Portal 100%), access to a 401(k)-retirement plan, paid parental leave, you may also accrue 3 weeks of paid vacation and will be eligible for 12 or more paid holidays per year as well as sick time. ITAR Statement This position may involve access to technical data and defense-related materials controlled under the International Traffic in Arms Regulations (ITAR). Eligibility to access ITAR-controlled items requires that candidates be U.S. persons , which includes U.S. citizens, lawful permanent residents, and other protected individuals as defined by U.S. law. Employment is contingent upon verification of ITAR eligibility and, where applicable, obtaining any required export authorization or license. Equal Opportunity Statement All qualified applicants will receive consideration for employment without regard to race, color, religion, sex, sexual orientation, gender identity, national origin, disability, or status as a protected veteran.