In-Situ Hyperspectral Absorption and Backscattering Sensors for Ocean Color and Biogeochemistry Research

Accurate measurements of in-water inherent optical properties (IOPs) such as absorption and backscattering, along with coincident in-situ and satellite-measured radiometry, are key to refining and calibrating algorithms used by hyperspectral satellite missions such as NASA PACE to derive ocean color data products. The accuracy of hyperspectral ocean color products, such as phytoplankton community composition, is therefore linked to the accuracy of in-situ IOP measurements. However, current instrumentation for in-situ absorption and backscattering measurements has been limited to either single- or multi-spectral wavelengths or to hyperspectral wavelengths that do not entirely meet the wavelength range and resolution requirements of PACE and other hyperspectral remote sensing missions. Advancements in instrumentation are therefore necessary to expand the range, resolution, and sensitivity of in-situ absorption and backscattering measurements to support these missions and the development and distribution of accurate ocean color data products. Additionally, advancements in hyperspectral absorption and backscattering sensors can offer new insights into studying particulate and dissolved materials in the ocean in support of biogeochemistry research.

We have recently developed and commercialized submersible hyperspectral absorption (Hyper-a) and backscattering (Hyper-bb) instruments to meet the needs of current (e.g., PACE) and future (e.g., GLIMR, SBG) hyperspectral remote sensing missions. The Hyper-bb is a single-angle backscatter sensor that utilizes a broadband LED source, scanning linear variable filter assembly, and sensitive photomultiplier tube detector. The Hyper-a is an absorption sensor that utilizes a xenon flash lamp, dual spectrometers (signal and reference), and a pump-through Lambertian integrating cavity that reduces measurement uncertainty due to scattering errors characteristic in a reflective tube design. Both sensors are designed to enable user calibration, reducing cost and downtime typically associated with sending the instrument back for factory calibration.

We will present details related to the development of these two hyperspectral instruments as well as their engineering specifications and recent test results from laboratory studies and field work.