On the retrieval of lava-flow surface temperatures from infrared satellite data

The dual-band method has been widely used as the basis for determining lava surface temperatures from infrared satellite data; the method is based on the assumption that such surfaces can be described in terms of two end-member thermal components-hot cracks within a thermally homogeneous crust. The recent launch of the first orbiting hyperspectral imaging system, Hyperion, onboard the National Aeronautics and Space Administration Earth Observing-1 (EO-1) satellite heralds a new era of space-based hyperspectral data collection that will allow more detailed models of lava-flow surface temperatures to be developed and parameterized. To this end, we have analyzed thermal images of active pahoehoe lava flows collected on Kilauea volcano; Hawaii, by using a forward looking infrared (FLIR) 595 PM ThermaCAM, in order to assess the number of thermal components required to characterize the surface temperatures of active lava-flow surfaces. The FLIR images show that an active lava-flow surface comprises a continuum of temperatures that define distinctive temperature distributions. Numerical model results reveal that the two-component dual-band method fails to resolve any of the major properties of the temperature distributions contained in these data (i.e., mode, skew, range, or dispersion). However, modeling five to seven thermal components allows all significant properties of the subpixel temperature distributions contained within the FLIR images to be determined. Thus, although the hyperspectral data provided by the EO-1 Hyperion yield as many as 66 wavebands in the 0.5-2.5 mum atmospheric window, useable data in 9-13 of these should be sufficient to perform accurate temperature characterization of active lava-flow surfaces from space.