A 300-element spatial radiometer was recently flown as part of the second Spatial Spectral Rocketborne Interferometer Telescope experiment. This instrument, housed in a high-off-axis-rejection telescope cooled to liquid helium temperatures, measured the spatial structure within six long-wavelength infrared spectral bands of the earthlimb. The radiometer used hybrid multiplexed focal planes with blocked impurity band detectors. The use of this technology enabled several enhancements to system performance. New data collection and analysis tools contributed significantly to the development and enhancement of this radiometer. Postflight analysis shows that the radiometer performed well during its sounding rocket flight.