DALEC shipborne radiometry

To support validation of atmospheric correction algorithms an autonomous ship-based system is operated that provides above-water hyper-spectral radiometry from Australian waters.

This system, the “Dynamic above water radiance and irradiance collector” (DALEC) was developed in Australia by “In situ Marine Optics (IMO)” and measures simultaneously sea and sky radiance together with down-welling hemispherical irradiance during autonomous ship-based deployments. The DALEC sensor head contains three compact hyper-spectral spectroradiometers (Carl Zeiss Monolithic Miniature Spectrometers), as well as a GPS and pitch and roll sensors, and is designed to be mounted on a boom positioned over the water, typically off the ship’s bow.

Deployments occur during daylight hours over multi-day voyages. The hyper-spectral data obtained from this instrument can be re-sampled for use in validation of a variety of satellite sensors. The instrument was initially deployed on the Australian Marine National Facility vessel, Southern Surveyor and collected data during 9 voyages between July 2011 and September 2012. This deployment resulted in refinement of the operating procedures and maintenance schedule requirements prior to redeployment on the Australian Institute of Marine Science (AIMS) vessel, RV Solander.

Recent match-up results with MODIS-Aqua and VIIRS showed good agreement with the DALEC observations. The DALEC will play a key role in providing southern-hemisphere validation support for the soon to be launched (Dec 2015) European Sentinel-3 Ocean Colour mission OLCI.

DALEC operation principle (left) and installation on the AIMS RV Solander
DALEC operation principle (left) and installation on the AIMS RV Solander