  The Probe far-Infrared Mission for Astrophysics (PRIMA) is a proposed space
observatory which will use arrays of thousands of kinetic inductance detectors
(KIDs) to perform low- and moderate-resolution spectroscopy throughout the
far-infrared. The detectors must have noise equivalent powers (NEPs) at or
below 0.1 aW/sqrt(Hz) to be subdominant to noise from sky backgrounds and
thermal noise from PRIMA's cryogenically cooled primary mirror. Using a Radio
Frequency System on a Chip for multitone readout, we measure the NEPs of
detectors on a flight-like array designed to observe at a wavelength of 210
microns. We find that 92% of the KIDs measured have an NEP below 0.1
aW/sqrt(Hz) at a noise frequency of 10 Hz.
