Hyper-Spectral Imager - 2

HSI-2 (Hyper-Spectral Imager 2) is a VNIR hyperspectral instrument manufactured by CAST and flown on HJ-2A for land observation and vegetation analysis.^[1] It operates as a Large Aperture Static Imaging Spectrometer (LASIS) using a Sagnac lateral shearing interferometer, a Fourier-transform architecture that differs fundamentally from dispersive-grating pushbroom designs.^[2] The instrument covers 450 to 950 nm across 128 spectral channels with a nominal sampling interval of approximately 4 nm, though the interferometric acquisition produces a non-uniform wavenumber distribution in raw data that results in variable per-channel bandwidths across the range.^[2] Native ground sampling distance is cited as 48 m by Gunter's Space Page^[3] and the eoPortal HJ-2 mission overview^[1]; the WMO OSCAR instrument record lists 100 m, which likely reflects a resampled delivered product.^[4] Swath width is 50 km.^[4] The spectral range and channel count suit detailed land-cover classification and vegetation index retrieval; cross-calibration with ZY1-02D/AHSI has been demonstrated to support multi-mission harmonisation of VNIR hyperspectral time series.^[2]