How do you estimate market size for a niche defence electronics segment?

For sparse defence segments like radar components, I'd triangulate from contract award databases (USASpending.gov, FPDS, and UK Defence Contracts Online are goldmines), then cross-check against public earnings calls from primes like Raytheon or L3Harris who often break out segment revenue. You can also reverse-engineer SAM by pulling export license data from BIS and applying rough ASP assumptions — not perfect, but gets you in the right ballpark for a credible TAM/SAM story.