Senior Flight Software Engineer (TS Cleared)

The role

You will design, develop, and own mission-critical software for satellite systems throughout the full software lifecycle. You will work with mission operations, GNC, and hardware teams to architect systems and prototype ideas.

What you will do

• Design, develop, and own mission-critical software for satellite systems.
• Develop rapid, iterative software for bench and development testing.
• Deliver robust, reviewed and validated software to manufacturing and flight systems.
• Plan and execute unit, integration, and system-level testing.
• Diagnose and resolve defects to ensure software quality and performance.
• Collaborate cross-functionally to establish product requirements and technical roadmaps.
• Support spacecraft commissioning during launch and early operations.
• Troubleshoot software to ensure critical flight systems remain functional.

Required qualifications

• U.S. Citizenship
• Active Top Secret or Top Secret/SCI clearance
• 8+ years of total flight software experience
• Bachelor’s degree in CS, EE, or equivalent
• Strong proficiency in programming languages such as C++, Python, or Rust

Nice to have

• Experience developing, testing, deploying, and troubleshooting mission-critical satellite software
• Experience with real-time software on distributed hardware platforms
• Knowledge of embedded and real-time operating systems (e.g., Embedded Linux, Yocto, Buildroot, FreeRTOS, VxWorks)
• Experience writing and debugging low-level device drivers (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, data serialization, and encryption
• Experience translating requirements into technical solutions and defining technical roadmaps
• Experience supporting spacecraft commissioning during launch and early operations
• Experience with version control, configuration management, automated testing, and CI/CD pipelines

Benefits

• Equity in Apex
• 100% company-paid medical, dental, and vision for you and dependents
• $100k life insurance at no cost
• 15 to 20+ days vacation annually
• 10 paid holidays
• 100% match on first 3% and 50% on next 2% 401(k) matching
• 8 weeks paid parental leave
• Childcare reimbursement up to $350/day for work-related travel
• Daily catered lunch and unlimited snacks
• Monthly office socials, pickleball tournaments, and run club
• Dream desk setup

Before you apply

• Must be a U.S. Citizen
• Must possess an active Top Secret or Top Secret/SCI clearance
• Must be able to obtain and maintain access to additional programs as needed
• Must qualify as a U.S. Person or obtain required export authorizations

About the company

Apex manufactures satellite buses at scale using software, vertical integration, and hardware. They are a fast-growing startup that has raised more than $500M in funding.