On-orbit characterization and effects of dark offsets from Orbital Sidekick's GHOSt hyperspectral constellation (Conference Presentation)

Orbital Sidekick's GHOSt (Global Hyperspectral Observation Satellite) constellation had launches in April and June 2023 and in March 2024. These sensors are among the first ever commercial space-based hyperspectral sensors that span the VIS-SWIR range. Post launch, a calibration campaign began to characterize each sensor's optical and radiometric quality. One of the areas of interest that were trended over time are the dark offsets, which are images taken with a closed shutter in front of the entrance slit of the spectrometer. Especially for SWIR-sensitive cryo-cooled detectors, a significant sensitivity in dark offsets is thought to be observed based on season, albedo, and spacecraft orientation. As a result, unlike a CMOS sensor, a "dark" must be collected at least before image collection and subtracted before imaging tasks. This paper discusses the difference in darks between space-based and ground based sensors and impacts on spatial/spectral noise and bad pixel computation.