Measurement of the radiant flux scattered back into space from the sunlit layer of the world�s oceans provide quantitative information about the biological and biogeochemical constituents of these waters that is necessary for accurate understanding of the global carbon cycle, ocean dynamics, and resource management. Satellites provide global coverage of these water-leaving radiance, but they cannot be calibrated before launch with the uncertainties required to produce meaningful results. The solution is to provide continuous in situ measurements of the water-leaving radiance, using accurate, well characterized, robust field instruments and solid experimental design. The Marine Optical Buoy (MOBY) has provided this vicarious calibration function since 1996, to the great benefit of the NASA programs designed to study Earth from space to advance scientific understanding of marine productivity and improve carbon cycle and ecosystem models. The technology exists to substantially reduce the measurement uncertainties of these in situ measurements, and we propose to design and build an instrument suite that will realize these capabilities. The result will be the infrastructure required to replace the aging MOBY instruments, in addition to a versatile system devoted to addressing critical scientific questions in coastal regions, shallow water, and novel deployment methods. This work directly supports the NASA objective of developing comprehensive sets of long-term, consistent, and calibrated data and products that are valid across multiple missions and satellite sensors.
We refer to the optical sensor system as the Multi-Input Fiber Spectrograph (MIFS) and the instrument suite as the Advanced Hyperspectral Autonomous Buoy (AHAB). A key feature of the MIFS is the simultaneous acquisition of the required light fields (MOBY operates in a sequential fashion), and this results in lower uncertainty because the impact of the natural environmental variability is reduced. Other features include daily monitoring of the internal and system-level radiometric responsivity and elimination of bio-fouling on the optical elements using UV LEDs. A key feature of AHAB is the transfer of all power generation to the mooring buoy, which results in a small optical buoy (containing MIFS) that can be deployed without depending on large oceanographic vessels. The lifetime will be increased compared to MOBY, from 3 months to 6 months for the optical buoy and from 1 year to 2 years for the mooring buoy. We will build and demonstrate the feasibility of MIFS and AHAB in this three year effort.
