Abstract for presentation at The 13th Australasian Remote Sensing and Photogrammetry Conference

A compact spectroradiometer for sea-level transect measurements of remote sensing reflectance (Rrs) spectra

  • Dr Miles Furnas, Australian Institute of Marine Science, Australia
  • Mr Matt Slivkoff, Australian Institute of Marine Science and Curtin University, Australia
  • Mr Wojciech Klonowski, Curtin University, Australia
  • Mr Paul Millers, Australian Institute of Marine Science, Australia
  • Mr Chris Robertson, Australian Institute of Marine Science, Australia
  • Mr Leon Majewski, Curtin University, Australia

    • Remote sensing retrievals of the optical and bio-geochemical properties of marine waters rely on accurate determinations of remote sensing reflectance (Rrs) spectra. Sea-level spot (100-101 m2) validation measurements of downwelling (ED), water-leaving (LW) and open sky (LSKY) radiance, and of bio-optical properties, assume spatial homogeneity over pixel-sized areas (104-106 m2). This assumption may not hold in heterogeneous coastal waters. We have developed a 3-channel continuous sampling spectroradiometer (DALEC: Downwelling Above-Water Radiance and Irradiance Collector) to measure surface reflected skylight corrected ocean colour spectra (340-1100 nm, 256 spectral bins) from a moving ship over multi-kilometre transects. Three solid state spectrometers simultaneously measure downwelling irradiance (ED), water-leaving radiance (LW) and open sky radiance (LSKY) spectra at 0.5 to 10 second intervals. The LSKY spectrum is used to remove surface reflectance contamination from each water-leaving radiance spectrum. The DALEC contains an internal GPS to provide position and heading information for each set of spectra, and can be combined with other instrumentation (thermosalinograph, chlorophyll fluorometer, nephelometer, spectral backscatter sensor, spectral absorption sensor) in a de-bubbled running seawater system to contemporaneously measure near-surface biological and optical properties. Spectral, bio-optical and biological data can be considered on a point-by-point basis, or averaged in pixel-sized bins to weight Rrs values over spatial scales resolved by satellite sensors. To date, >500 km of transects have been run in a variety of coastal settings to gather information for ocean colour algorithm development and validation.

    Conference Organiser - ICMS Pty Ltd