Future space-based observatories imaging in the 4-40 ìm spectral regime will be passively cooled. The objective of this research effort is to demonstrate near theoretical performance of bolometer-based infrared focal plane arrays (FPAs) covering the 4-40 ìm wavelength region by operating the FPA at reduced temperature. Amorphous silicon-alloy resistive bolomoters exhibit increased temperature coefficient of resistance when cooled below room temperature and are well suited for operation over the 30K-200K detector temperature range. Detector process optimization will allow performance levels close to theoretical limits. The cooled bolometer is compatible with advanced readout technologies, such as switched capacitor integrators, offered by Black Forest Engineering. The amorphous silicon-alloy bolometer process, optimized on Phase I for cryogenic operation, will be a basis for future large formant monolithic 1024x768 format FPAs fabricated on Phase II to support NASA passively cooled imaging applications and DoD/commercial cryo-cooled systems.