Abstract
The Plankton, Aerosol, Cloud, ocean Ecosystem (PACE) mission extends and improves the data record of NASA’s satellite observations of global ocean biology, aerosols, and clouds. The Ocean Color Instrument (OCI) is the primary sensor on-board the PACE platform. The OCI is a scanning radiometer with hyperspectral coverage from the ultraviolet (UV) to the near infrared (NIR) wavelength range and a fiber-coupled multiband filter spectrograph in the short-wave infrared (SWIR) spectral region. The OCI Flight Unit completed system level testing in November 2022 at the Goddard Space Flight Center (GSFC). Part of the pre-launch test campaign used the monochromic Goddard Laser for Absolute Measurement of Radiance (GLAMR) source to characterize the relative spectral response of all OCI bands. The OCI has 960 hyperspectral bands and 9 filter bands. This presentation presents the methods used to interpolate the Relative Spectral Response (RSR) for the hyperspectral in-band channels based on in-band modeling and all other adjustments to the measured spectral response. Limited test time restricted the wavelength coverage to 1 nm steps with 0.2 nm steps for only a few hyperspectral bands. It was found that the 1 nm steps did not capture the in-band profile well enough to derive accurate characterization. These methods use the 0.2 nm stepped bands and a combination of multiple bands to build an in-band model that is fit to each band. This improved the accuracy of the RSR and the derived spectral characterization such as band center, bandwidth, and out-of-band response. Additional adjustments include reprocessing the Level 1A files to Level 1B that contain calibration for linearity, temperature, cross talk, and hysteresis.
PACE OCI Pre-Launch Relative Spectral Response with In-Band Modeling and L1B Corrections
The Plankton, Aerosol, Cloud, ocean Ecosystem (PACE) mission extends and improves the data record of NASA’s satellite observations of global ocean biology, aerosols, and clouds. The Ocean Color Instrument (OCI) is the primary sensor on-board the PACE platform. The OCI is a scanning radiometer with hyperspectral coverage from the ultraviolet (UV) to the near infrared (NIR) wavelength range and a fiber-coupled multiband filter spectrograph in the short-wave infrared (SWIR) spectral region. The OCI Flight Unit completed system level testing in November 2022 at the Goddard Space Flight Center (GSFC). Part of the pre-launch test campaign used the monochromic Goddard Laser for Absolute Measurement of Radiance (GLAMR) source to characterize the relative spectral response of all OCI bands. The OCI has 960 hyperspectral bands and 9 filter bands. This presentation presents the methods used to interpolate the Relative Spectral Response (RSR) for the hyperspectral in-band channels based on in-band modeling and all other adjustments to the measured spectral response. Limited test time restricted the wavelength coverage to 1 nm steps with 0.2 nm steps for only a few hyperspectral bands. It was found that the 1 nm steps did not capture the in-band profile well enough to derive accurate characterization. These methods use the 0.2 nm stepped bands and a combination of multiple bands to build an in-band model that is fit to each band. This improved the accuracy of the RSR and the derived spectral characterization such as band center, bandwidth, and out-of-band response. Additional adjustments include reprocessing the Level 1A files to Level 1B that contain calibration for linearity, temperature, cross talk, and hysteresis.