Location: Little Paxton, PE19 6BN (Head Office) Hybrid working Clearance: SC required Salary: Competitive, with excellent benefits Why join us? At MASS, people are at the heart of what we do. As part of ourElectronic Warfare Support Group (EWOS), youll work alongside over 60 engineers, scientists, and specialists, helping to keep people and platforms safe. We offer a comprehensive reward package, including: 25 days annual leave (including up to 3 days Christmas shut-down) Buy or sell up to 5 days leave Two pension schemes to choose from Private medical & dental insurance (with family discounts) Life assurance up to 4x salary Multiple savings schemes Electric/hybrid car leasing scheme & cycle-to-work scheme Annual Wellness Allowance Retail discounts Continuous learning and career development support The role Were looking for a Principal Modeller to lead our Countermeasure Development team. This is a unique opportunity to take ownership of our in-house simulation tool, CounterWorX, used to model complex physical interactions and countermeasure performance in real-world scenarios. Youll oversee a team of engineers, guide technical delivery, and line manage senior engineers. Youll also collaborate with our software development team, contributing to the assurance of software products before release. Our teams split their time between the office and home (typically 3 days in, 2 days remote), offering the perfect mix of flexibility and collaboration. What youll bring Were looking for someone who combines deep technical expertise with leadership experience. Essential: Strong knowledge of RF and/or EO/IR countermeasures across multiple domains Understanding of radar theory and modes of operation Degree-level understanding of Physics/Mathematical principles Proven line management experience Experience across the full engineering lifecycle (requirements, design, prototyping, testing, integration, deployment) Ability to write detailed analysis and technical reports Experience providing technical leadership and mentoring junior engineers Desirable: Programming in MATLAB, Simulink or Python Familiarity with CONOPS and TTPs for EW platforms/systems Experience deploying executable applications Technical bid writing and estimation experience Knowledge of emerging technologies in the EW domain Experience creating technical roadmaps for in-house tools About you Youll be comfortable leading from the frontbalancing hands-on modelling and analysis with coaching and developing your team. With a strong defence background, particularly in radar, EO/IR systems, or countermeasures, youll have the opportunity to shape a growing team and directly impact operational capability. About MASS MASS is a trusted, independent global technology company, delivering secure, advanced digital services for defence and other highly regulated sectors. With our heritage in electronic warfare and data security, we provide tailored, innovative, and resilient solutions that give our customers the edge. Wellbeing is at the core of our culture. From mental health first aiders to our employee assistance programme, we support our people to flourish and achieve their full potential. Were proud to be an equal opportunities employer, offering a workplace where everyone is valued, supported, and empowered to make an impact. Ready to take the lead in shaping advanced countermeasure solutions? Apply today and see how a career with MASS could work for you.