Gao, Bo-Cai: Naval Research Laboratory (Project Lead)
Project Funding:
2012 - 2016
NRA: 2011 NASA: HyspIRI Preparatory Airborne Activities and Associated Science and Applications
Funded by NASA
Abstract:
In response to the NASA research announcement - A.26 HyspIRI Preparatory Airborne Activities and Associated Science and Applications Research, we propose to further develop and enhance atmospheric correction and spectrum-matching techniques for the characterization and analysis of hyperspectral imaging data to be acquired with the present AVIRIS instrument (referred as AVIRIS-Classic) and the next generation AVIRIS (referred as AVIRISng) operating in the solar spectral region between approximately 0.35 and 2.5 micron. The atmosphere-corrected hyperspectral imaging data will be most useful for research and a variety of applications, and to answer many key science questions originally identified in the National Research Council Decadal Survey and refined recently by the HyspIRI Science Study Groups and research community. These questions include, but not limited to: What is the composition, function, and health of land and water ecosystems? How are these ecosystems being altered by human activities and natural causes? How do these changes affect fundamental ecosystem processes upon which life on Earth depends?
The solar radiation on the sun-surface-sensor path is affected by absorption and scattering effects from atmospheric gases and aerosols. Accurate modeling of these effects is required in order to derive surface reflectance spectra from imaging spectrometer data. Previously, we developed radiative transfer modeling algorithms for atmospheric corrections over land and water surfaces. We propose to use these algorithms to derive the surface reflectance spectra from AVIRIS-Classic and AVIRISng data to be acquired through the HyspIRI preparatory Airborne Activities in the near future. The retrieved reflectance spectra using these algorithms can still contain residual atmospheric absorption and scattering effects. We plan to use field-measured surface reflectance spectra, such as those collected over a large playa during a calibration experiment, to renormalize the retrieved reflectance spectra and to remove the residual errors.
Since the early 1990s, accurate radiometric calibrations of any imaging spectrometer data below 0.45 micron have remained to be a problem using NIST-traceable calibration lamps. Because the lamps operate at a temperature of approximately 2000 K, they do not emit sufficient amount of photons in the blue to permit accurate radiometric calibrations in the blue spectral region. We propose to derive additional gain curves for AVIRIS-Classic and AVIRISng bands below 0.45 micron based on modeling the spectrally flat reflectance spectra of white clouds in the 0.35 - 0.9 micron wavelength range. This empirical technique has recently been used successfully in radiometric calibration of hyperspectral imaging data collected with HICO (Hyperspectral Imaging for the Coastal Ocean) onboard the International Space Station.
AVIRISng is equipped with arrays of area detectors. Small artifacts, such as spectral smile in the spectral domain, will likely be present in the measured data. We propose to upgrade our present versions of spectrum-matching algorithms for wavelength and spectral resolution calibrations. We will apply the updated algorithms to characterize and verify the wavelength and spectral resolution calibrations of AVIRIS and AVIRISng data for every pixel in the cross track direction, and to monitor the stability of the instruments with time.
More details may be found in the following project profile(s):
