  We present a highly frequency multiplexed readout for large-format
superconducting detector arrays intended for use in the next generation of
balloon-borne and space-based sub-millimeter and far-infrared missions. We will
demonstrate this technology on the upcoming NASA Next Generation Balloon-borne
Large Aperture Sub-millimeter Telescope (BLAST-TNG) to measure the polarized
emission of Galactic dust at wavelengths of 250, 350 and 500 microns. The
BLAST-TNG receiver incorporates the first arrays of Lumped Element Kinetic
Inductance Detectors (LeKID) along with the first microwave multiplexing
readout electronics to fly in a space-like environment and will significantly
advance the TRL for these technologies. After the flight of BLAST-TNG, we will
continue to improve the performance of the detectors and readout electronics
for the next generation of balloon-borne instruments and for use in a future
FIR Surveyor.
