Embedded Flight Software Engineer (TS/SCI Cleared)

Spacecraft 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 Role

As a Senior Embedded Software Engineer on Apex's 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.

Responsibilities

• Develop the low level software that configures and drives the processor peripherals and communication interfaces on our avionics.

• Write and debug the device drivers for the sensors, actuators, and components across the bus.

• Implement onboard algorithms, including closed loop control and the logic that detects and responds to faults such as failed sensors or radiation upsets.

• Design, 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.

• With a focus on embedded software and hardware designs, 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.

Requirements

• U.S. Citizenship (must possess the ability to access export-controlled data)

• Active Top Secret clearance with SCI access and SAP eligibility

• 8+ years writing C/C++ for embedded systems, ideally in spacecraft, robotics, automotive, or other hardware that interacts with the physical world

• Bachelor’s degree in CS, EE, or equivalent

• Strong proficiency in programming languages such as C++, Python, or Rust

Preferred

• 3+ years of flight software experience

• Experience developing firmware for microcontrollers, either bare-metal or on an RTOS.

• Comfort with hardware/software integration, including reading schematics and using tools like oscilloscopes and logic analyzers to bring up new hardware.

• A solid understanding of microcontroller and microprocessor architecture, including memory, buses, and DMA.

• FPGA development experience.

• Experience bringing up new avionics or flight hardware from first power-on.

• Experience with satellite attitude control systems (ACS), including reaction wheels, magnetorquers, and small thrusters, and sensors

• Experience driving motors and power electronics or reading feedback sensors such as encoders and current monitors.

• Experience 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 create

• Best-in-class healthcare: 100% company-paid medical, dental, and vision for you and your dependents, plus $100k life insurance at no cost

• Comprehensive PTO package: Starting at 15 days vacation, growing to 20+ days annually, plus 10 paid holidays

• Competitive 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 travel

• Daily catered lunch and unlimited snacks: To keep you fueled throughout the day

• Vibrant community Monthly office socials, pickleball tournaments, run club, and gatherings for you and your family

• Your dream desk setup All the tools you need to be your most productive self

• World-class Playa Vista office: With the benefit of in-person collaboration with amazing coworkers and flexibility to integrate work and life

• Real impact opportunity: Work alongside experts from aerospace, new space, and other cutting-edge industries to make a lasting difference