The Assist-II from LR Tech is an Atmospheric Sounder Spectrometer that has a spectral range of 500 - 5000 cm^-1. It has a spectral resolution of 0.1 nm - 1000 nm and a nominal beam diameter of 2.54 cm at the beam stop. This spectrometer has an optical throughput of 0.00805 sr·cm² and a field of view (FOV) of 45 mrad with uniformity ± 5 %. It has radiometric noise-equivalent spectral radiance (NESR) of 2.5 x 10^-9 W/sr/cm² (at 1300 cm^-1) and 2.5 x 10^-10 W/sr/cm² (at 2000 cm^-1). This spectrometer has a raw measurement rate of 1 spectra/s and an atmospheric profile rate of 0.5 profile/min at maximum resolution. It has an effective emissivity of 0.9985 and an aperture diameter of 6.98 cm at the cavity entrance.

The ASSIST-II spectrometer has mid-wave IR (InSb) and long-wave IR (HgCdTe (MCT)) detectors and built-in calibration units composed of two high emissivity blackbodies. It is compatible with Edgar instrumental control and data acquisition software. This spectrometer requires an AC voltage of 115 - 230 V and consumes 1 - 3 A of power. It is available in an atmospheric temperature/moisture profile package (standard) and trace gases (GHGs) concentration profile package & emissivity/skin temperature retrieval package is optionally available. This spectrometer measures 90.7(L) x 78.7 (W) x 50 (H) cm (ASSIST-II Instrument) & 96.2 (L)x 182.2 (W) x 102.5 (H) cm (ASSIST-II Environmental Enclosure) and is ideal for research, environmental and airborne applications.