Software Engineer in Welwyn Garden City

SII is an international group specialising in digital services and engineering, working alongside major industrial and service-sector companies to accelerate their digital transformation. Present in 21 countries and supported by the expertise of more than 16,000 employees, the group designs and delivers innovative and sustainable technological solutions. Joining SII means becoming part of a company where team spirit, autonomy, and professional growth are at the heart of the employee experience. Our promise, “Let’s Tech Together,” reflects our ambition: to build a technological future together that is useful, inclusive, and driven by innovation. With five strategic offices in Belfast, Chester, Farnborough, London and Oxford, we work in partnership with our customers UK-wide to deliver high-impact engineering solutions. SII UK is a trusted Aerospace and Defence engineering partner, supporting the delivery of complex, mission‑critical programmes while helping to shape the future of innovation across next‑generation systems and technologies. Our teams contribute daily to creating a fulfilling, stimulating and career development focused work environment. True to our human‑centred values, we are committed to making SII UK a Great Place To Work®, having been certified 5 years running.

THE OPPORTUNITY

We are seeking a Software Engineer who will be responsible for the design, development and integration of a Hardware‑in‑the‑Loop (HIL) simulator, as well as supporting technical exchanges with other space engineering disciplines. You will work closely with system engineering teams to ensure the successful development, integration and delivery of test benches used to validate spacecraft and rover systems.

KEY RESPONSIBILITIES

• Analyse technical requirements and contribute to system and software design
• Develop and implement simulator software primarily in C++, with Java used as the test language
• Integrate, test and deliver HIL test benches within a Linux environment
• Interface with hardware and support system integration activities
• Provide technical follow‑up and coordination with internal and external teams
• Support verification, validation and testing activities throughout delivery

SKILLS & EXPERIENCE

• Strong practical experience in C++ and Java
• Real‑time software design and debugging in a Linux environment
• Proven experience in Hardware‑in‑the‑Loop (HIL) design and implementation
• Solid understanding of multi‑process and/or multi‑threaded software architectures, ideally for hardware interfacing
• Experience with testing methodologies and unit testing frameworks
• Object‑oriented analysis and design using UML (or equivalent)
• Understanding of machine‑to‑machine communication protocols
• Strong knowledge of the software development lifecycle
• Familiarity with design patterns and best‑practice coding standards
• Excellent written and verbal communication skills, with the ability to explain complex technical concepts to non‑technical stakeholders
• ECSS software standards
• Space communication protocols
• SpaceWire
• ECSS CAN

BENEFITS

• Competitive Basic Salary
• 6% Employers Contribution + 6% as a salary sacrifice
• Private Medical Insurance, Life Cover and Income Protection
• 25 days holiday
• 10 days full sick pay per year
• Cycle to Work & TechScheme
• Corporate access to the Udemy platform

* If you're applying for a role requiring security clearance, please be aware that foreign or dual nationality is not an automatic bar, however certain posts may have restrictions which could affect those who do not have sole British nationality or who have personal connections with certain countries outside the UK.