Lead, Mission Software Engineer

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. Lead, Mission Software Engineer Castelion is seeking a Lead, Mission Software Engineer to help define and build the software that connects our products into an integrated mission capability. Mission Software spans Castelion’s full product portfolio, including weapons, launchers, command-and-control systems, sensors, mission planning tools, and external platforms. Engineers on this team build the software that allows operators and systems to plan missions, exchange targeting and sensor data, command assets, initialize and employ weapons, and execute missions end to end. As a Lead Mission Software Engineer, you will own major software capabilities and technical architecture across this mission stack. You will work across product boundaries, drive interfaces between systems, and help establish the software patterns that allow Castelion’s products to operate together as a cohesive system. This is a hands-on technical leadership role. You will write, review, test, and commit production code while also leading architecture, mentoring engineers, and driving complex integrations from concept through flight test and fielding. Responsibilities • Lead the architecture, development, integration, and deployment of mission software across weapons, launchers, C2 systems, sensors, and mission planning. • Own major software capabilities from early requirements and architecture through implementation, integration, test, and operational deployment. • Develop and integrate command-and-control software connecting operators, sensors, weapons, launchers, tactical networks, and external platforms. • Define software architectures, APIs, data models, and interfaces that allow Castelion products to operate together as an integrated mission system. • Develop software interfaces between Castelion products and aircraft, launchers, mission computers, fire-control systems, sensors, and government C2 systems. • Implement communications across interfaces and protocols such as Ethernet, TCP/UDP, CAN, MIL-STD-1553, MIL-STD-1760, and other tactical interfaces. • Translate operational concepts, system requirements, and ICDs into scalable software architectures and production implementations. • Build tools, simulators, and test infrastructure for software-in-the-loop, hardware-in-the-loop, and system-level testing. • Lead debugging and root-cause efforts for complex issues spanning application software, embedded systems, networks, avionics, sensors, and hardware. • Write and review production code using modern Git-based workflows, automated testing, and continuous integration. • Establish strong software engineering practices around code quality, testability, interfaces, and system architecture. • Mentor software engineers and provide technical guidance across mission software efforts. • Partner closely with flight software, avionics, guidance and navigation, vehicle engineering, test, and integration teams. • Work directly with government customers, platform partners, operators, and external engineering teams during integration and fielding. • Support integration and test activities from laboratory testing through ground and flight test. Basic Qualifications • Bachelor's degree in Computer Science, Computer Engineering, Electrical Engineering, Aerospace Engineering, or a related technical field. • 7+ years of professional software engineering experience. • Strong software development experience in C++, Rust, Python, Go, C, or similar languages. • Demonstrated experience owning and delivering complex software systems or major software capabilities. • Experience designing software architectures and interfaces across distributed or integrated systems. • Experience contributing to and leading development in a production software codebase using Git, code review, automated testing, and CI/CD. • Strong understanding of software architecture, APIs, networking, data serialization, concurrency, and distributed systems. • Experience developing software that interfaces with hardware, embedded systems, or external services. • Experience debugging complex integrated software systems across software and hardware boundaries. • Ability to lead ambiguous technical efforts and drive them from initial definition through implementation and test. • Strong communication skills and the ability to work across software, hardware, systems, operations, and customer teams. • Ability to obtain and maintain a U.S. security clearance. Preferred Skills and Experience • Experience developing mission planning, C2, fire control, targeting, autonomy, sensor integration, or weapon-system software. • Experience leading software development for weapons, launchers, aircraft avionics, autonomous systems, spacecraft, robotics, or other mission-critical systems. • Experience with MIL-STD-1553, MIL-STD-1760, UAI, CAN, Ethernet, TCP/UDP, protobuf, tactical data links, or military mission systems. • Experience with geospatial software, coordinate systems, targeting, route planning, trajectory generation, or mission-data processing. • Experience architecting systems that integrate sensors, shooters, operators, and command-and-control systems. • Experience with embedded or real-time software. • Experience developing Linux-based applications and services. • Experience with SIL, HIL, vehicle-in-the-loop, or flight-test environments. • Experience leading complex system-level integration and test campaigns. • Experience mentoring and technically leading software engineering teams. • Active Secret or Top Secret clearance. What Success Looks Like You will help define the software architecture that connects Castelion’s products across the mission — from sensing and targeting through mission planning, C2, launch, and weapon employment. You will own critical software capabilities, set technical direction, and ensure those systems move successfully from architecture and production code into integrated system test, flight test, and operational fielding. You will also help grow the Mission Software team by raising the technical bar, mentoring engineers, and establishing the patterns that allow Castelion’s products to operate together as a complete mission system. 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 a