Senior Flight Software Engineer (TS Cleared)

Join Our MissionSpacecraft represent the most pressing unmet need across the entire aerospace industry. As more launch vehicles come online and the cost to orbit decreases, more companies launching payloads to space continue to emerge.For the first time in history, this influx of payload companies combined with reduced launch costs has resulted in a massive increase in need for commercial spacecraft platforms, known as satellite buses. These buses hold the payloads of our customers and are flown on launch vehicles.Apex manufactures these satellite buses at scale using a combination of software, vertical integration, and hardware that is designed for manufacturing. Our spacecraft enable the future of society: ranging from earth observation to communications and more.We'd love for you to join us on our mission of providing humankind access to the galaxy beyond our planet.About the RoleAs a member of the Flight Software team, you will design, develop, and own the software that brings our spacecraft to life. You will tackle the hardest problems in autonomous systems and build robust software that enables reliable spacecraft operation 24/7, across every phase of a mission. You will work closely with our mission operations, GNC, and hardware teams to architect new systems, prototype ideas, and turn them into mission-critical software that ultimately flies.Experience in the space industry is not necessary to thrive at Apex. Instead, we are looking for motivated engineers who enjoy solving complex problems, balance technical rigor with practicality, and thrive in a dynamic, fast-paced environment.The Flight Software team is composed of three interconnected teams: high-level application software, operating system software, and embedded software. There is significant collaboration and crossover across these teams.ResponsibilitiesDesign, develop, and own mission-critical software for satellite systems throughout the full software lifecycle, from initial architecture and development through deployment and operations.Develop rapid, iterative software to support bench and development testing, as well as robust, rigorously reviewed and validated software delivered to manufacturing and flight systems.Plan and execute unit, integration, and system-level testing of satellite components, diagnosing and resolving defects to ensure software quality, reliability, and performance.Collaborate cross-functionally with systems, hardware, test, and operations teams to establish product requirements, define technical roadmaps, and drive successful execution.Support spacecraft commissioning during launch and early operations, troubleshooting software and ensuring critical flight systems remain functional and reliable throughout critical mission activities.RequirementsU.S. Citizenship (must possess the ability to access export-controlled data)Active Top Secret clearance with SCI access and SAP eligibility8+ years of total flight software experienceBachelor's degree in CS, EE, or equivalentStrong proficiency in programming languages such as C++, Python, or RustPreferredExperience developing, testing, deploying, and troubleshooting mission-critical satellite software from prototyping through flight operations.Experience with real-time software on distributed hardware platforms across multiple satellite products.Knowledge of embedded and real-time operating systems (e.g., Embedded Linux, Yocto, Buildroot, FreeRTOS, VxWorks).Experience writing and debugging low-level device drivers for hardware interfaces (e.g., SPI, I²C, UART, Ethernet, CAN, SpaceWire).Familiarity with satellite communication standards and protocols (e.g., CCSDS, ECSS).Familiarity with networking and secure communications (e.g., TCP/IP, UDP, TLS), data serialization (e.g., Protobuf, JSON, MessagePack), and encryption (e.g., AES, RSA).Experience translating requirements into technical solutions, defining technical roadmaps, and coordinating with cross-functional engineering teams to support project execution.Experience supporting spacecraft commissioning during launch and early operations.Experience with version control, configuration management, automated testing, and CI/CD pipelines for software build, deployment, and release.Why Join Apex?Apex believes in creating a work environment that you look forward to embracing every day. Our employees love working at Apex, and we want you to love it too. We're a fast-growing startup that has raised more than $500M in funding, and we invest heavily in our people from day one.What We Offer For Full-time Employees:Shared upside: Receive equity in Apex, letting you benefit from the work you createBest-in-class healthcare: 100% company-paid medical, dental, and vision for you and your dependents, plus $100k life insurance at no costComprehensive PTO package: Starting at 15 days vacation, growing to 20+ days annually, plus 10 paid holidaysCompetitive 401(k) plan: Generous matching - 100% match on first 3%, 50% on next 2%8 weeks paid parental leave: Plus childcare reimbursement up to $350/day for work-related travelDaily catered lunch and unlimited snacks: To keep you fueled throughout the dayVibrant community: Monthly office socials, pickleball tournaments, run club, and gatherings for you and your familyYour dream desk setup: All the tools you need to be your most productive selfWorld-class Playa Vista office: With the benefit of in-person collaboration with amazing coworkers and flexibility to integrate work and lifeReal impact opportunity: Work alongside experts from aerospace, new space, and other cutting-edge industries to make a lasting differenceAdditional Information:Compensation ranges are set by role, level, location, and alignment with market data. A candidate's specific level and base pay are determined case by case and may vary with job-related skills, education, experience, technical capabilities, and internal equity. Beyond base salary, full-time hires are also eligible for long-term incentives in the form of stock options, along with medical, dental, and vision coverage and a 401(k) retirement plan.ITAR RequirementsApex's work is governed by U.S. export control laws, including the International Traffic in Arms Regulations (ITAR) and the Export Administration Regulations (EAR). To be eligible for this role, applicants must either (1) qualify as a U.S. Person, meaning a U.S. citizen or national, a lawful permanent resident (green card holder), a refugee admitted under 8 U.S.C. § 1157, or an individual granted asylum under 8 U.S.C. § 1158, or (2) be able to obtain the required export authorizations from the U.S. Department of State, the U.S. Department of Commerce, or another applicable U.S. government agency. You can learn more about ITAR here.Equal Opportunity EmployerApex Technology, Inc. is an Equal Opportunity Employer. We celebrate diversity and are committed to creating an inclusive environment for all employees. Candidates and employees are always evaluated based on merit, qualifications, and performance. We will never discriminate on the basis of race, color, gender, national origin, ethnicity, veteran status, disability status, age, sexual orientation, gender identity, marital status, mental or physical disability, or any other legally protected status.