Temperature and Power Output of the Lava Lake in Halema´uma´u Crater, Hawaii, Using a Space-Based Hyperspectral Imager

Space-based remote sensing has the potential to monitor volcanic activity on a global basis. We use infrared hyperspectral data measured from space to study the temperature field and power output for a long-lived lava lake at Halema´uma´u crater, Hawaii. Overflights were made on two days: a night collect October 16, 2009, and a day collect on December 27, 2009. The basic data are short-wave infrared (SWIR) optical spectra recorded in the 900-2500 nm wavelength range. Spectra in the lava lake show strongly elevated radiance at SWIR wavelengths. We illustrate how corrections are made to account for solar radiance in the day image and for atmospheric water vapor for both images. We assume that the spectrum at each pixel can be modeled as a linear combination of cool and hot components, weighted by the area of each component. The inversion uses an exhaustive search algorithm over all possible combinations of hot temperature and fractional area of the hot component, with the cool component set to ambient temperature. Temperature and fractional area calculations can be used to compute radiant flux (power) emitted from each pixel, and from the lake as a whole. Power output changes from 15.1 MW in October to 24.0 MW in December. Approximately 223 Kg/s ( ~ 0.07 m³/s) of molten basalt is required to maintain the observed power output of the lava lake.