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 and technical excellence are decisive advantages - and we are building a team that can deliver real capability, not just concepts.

This is a rare opportunity to join at an early stage, where your work will directly shape critical systems, influence major technical decisions, and have immediate, real-world impact.

Ground Software Engineer

Ground Software Engineer on the Flight Software team is responsible for building the software systems that connect engineers to flight hardware throughout development, integration, testing, and flight operations. In this role, you will develop vehicle command and control systems, telemetry infrastructure, test automation tools, and mission-critical software that enables rapid iteration of Castelion's next-generation strike systems.

This position offers the opportunity to work at the intersection of software, hardware, and flight testing, making a direct contribution to accelerating vehicle development and increasing flight-test velocity.

Responsibilities

• Design, develop, and maintain software systems for vehicle command, control, telemetry, and test operations

• Build and support ground software infrastructure used for hardware-in-the-loop (HIL), integration, and flight testing

• Develop backend services, automation tools, telemetry pipelines, and operator-facing applications using Python and modern software frameworks

• Integrate software with avionics, flight computers, test equipment, and communication systems to enable end-to-end vehicle testing

• Support flight campaigns, system debugging, and root-cause investigations across software and hardware interfaces

Basic Qualifications

• Bachelor's degree in Computer Science, Electrical Engineering, Aerospace Engineering, or a related technical field

• 1+ years of professional software engineering experience with strong proficiency in Python

• Experience developing software on Linux systems and working with networking protocols such as TCP/IP and UDP

• Experience building backend services, distributed systems, automation frameworks, or hardware-integrated software systems

Preferred Skills and Experience

• Experience supporting aerospace, defense, robotics, autonomous systems, or other mission-critical hardware programs

• Experience with telemetry systems, real-time data processing, time-series databases, or data visualization platforms

• Experience with Docker, Kubernetes, CI/CD pipelines, and modern software deployment practices

• Experience supporting hardware-in-the-loop (HIL) testing, system integration, or flight test operations

• Experience developing operator interfaces, mission control systems, or engineering tools using React, Vue, or similar frameworks

Benefits And Perks

All full-time employees are granted meaningful long-term equity, sharing in the company's significant growth trajectory. We offer four (4) weeks of paid time off, ten (10) company-paid holidays, and comprehensive health benefits - including 100% employee-covered medical and strong dependent coverage, along with dental and vision plans. We also provide paid parental leave to support growing families, a $100 monthly fitness stipend to promote health and performance, and onsite EV charging for convenience. In addition, employees enjoy perks like catered meals, company-covered food during high-demand periods, and a fully stocked kitchen to stay fueled throughout the day.

While this position does not currently require a U.S government-issued security clearance, it may in the near future. Therefore, the ability to obtain and maintain a U.S. government–issued security clearance is required. U.S. citizenship is required, as only U.S. citizens are eligible for a security clearance.

Affirmative Action/EEO Statement

Employment with Castelion is governed on the basis of competence and qualifications and will not be influenced in any manner by race, color, religion, 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.