Instruments employing X-ray, gamma ray and particle detection are utilized in different sectors from medicine to industry and from basic to applied science. The solid-state detector array with detection ASIC is the primary technology of space-based high-energy astronomy missions that are managed by NASA in partnership with the international community1,2. A readout integrated circuitry (ROIC) specifically designed for photon resolving X-ray detection has been developed by Black Forest Engineering on prior NASA SBIR funding3. The BFE322 ROIC, bump bonded to a CdZnTe (CZT) 16x32 detector array, demonstrated single photon sensitivity, accurate X-ray energy determination, X-ray event time stamping, and low power dissipation (< 10 μW per pixel) at ambient temperature operation; this represents a significant advancement in detection capability. The proposed Phase I improves ROIC performance by using low 1/f noise 250 nm CMOS, in-pixel amplifier tuning to match detector capacitance and rad-hard-by-design (RHBD) to provide >500 kRad radiation tolerance. The Phase I design will be a 32x32 pixel format with 600 µm pixel pitch compatible with CZT and silicon detector arrays. The ROIC will be fabricated and hybridized to CZT on Phase II and demonstrated using a PocketQube or CubeSat mini-satellite test flight to establish a TRL> 6.