Far-infrared (far-IR) astrophysics missions featuring actively cooled telescopes will offer orders of magnitude observing speed improvement at wavelengths where galaxies and forming planetary systems emit most of their light. The PRobe far-Infrared Mission for Astrophysics (PRIMA), which is currently under study, emphasizes low- and moderate-resolution spectroscopy throughout the far-IR. Full utilization of PRIMA’s cold telescope requires far-IR detector arrays with per-pixel noise equivalent powers (NEPs) at or below 1 ×10-19W/√{Hz} . We are developing low-volume aluminum kinetic inductance detector (KID) arrays to reach these sensitivities. We describe the development of our long-wavelength (80-265 μ m ) array approach and present multitone measurements of a 1008-pixel arrays. We measure an NEP below 1 ×10-19W/√{Hz} for 73% of the measured pixels.
