Cash develops space astrophysics instrumentation - he invented the petal-shaped starshade external occulter for direct spectroscopy of habitable exoplanets and biosignatures, and pioneers X-ray interferometry for ultra-high angular resolution and X-ray grating spectrometers. For context, this complements the established paradigm of NV-diamond ensemble magnetometry (Hahn-echo/DEER, nanoscale NMR, T1 relaxometry) operating near pT/√Hz sensitivity.