Hyperspectral sensor characteristics needed for coastal ocean science

The complexity of the coastal ocean, particularly when the bottom is visible, necessitates the use of hyperspectral imagery for remote measurement of bathymetry, bottom type, and water properties. This is in contrast to the open ocean where water column properties alone are of interest and for which the use of multispectral imagery is normally sufficient. The Remote Sensing Division of the NRL has had a program to develop hyperspectral imagery for coastal studies for more than 10 years. The Ocean Portable Hyperspectral Imager for Low-Light Spectroscopy (Ocean PHILLS), the most recent version of NRL´s imaging spectrometer, is designed specifically for this application. It uses a thinned, backside-illuminated CCD for high sensitivity and an all-reflective spectrograph with a convex grating in an Offner configuration to produce a nearly distortion-free image. The sensors, which are constructed entirely from commercially available components, have been successfully deployed on numerous aircraft based experiments since 1999. After data collection is complete the data are geolocated, calibrated, atmospherically corrected and used for a variety of ocean and land products. In this presentation, we describe the instrument design, with emphasis on the specifications required for observing the coastal ocean. We also present examples of remote-sensing reflectance data obtained from the LEO-15 site in New Jersey that agree well with ground-truth measurements