Michael L. Eastwood

Imaging spectroscopy and the airborne visible/infrared imaging spectrometer (AVIRIS)

Abstract Imaging spectroscopy is of growing interest as a new approach to Earth remote sensing. The Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) was the first imaging sensor to measure the solar reflected spectrum from 400 nm to 2500 nm at 10 nm intervals. The calibration accuracy and signal-to-noise of AVIRIS remain unique. The AVIRIS system as well as the science research and applications have evolved significantly in recent years. The initial design and upgraded characteristics of the AVIRIS system are described in terms of the sensor, calibration, data system, and flight operation. This update on the characteristics of AVIRIS provides the context for the science research and applications that use AVIRIS data acquired in the past several years. Recent science research and applications are reviewed spanning investigations of atmospheric correction, ecology and vegetation, geology and soils, inland and coastal waters, the atmosphere, snow and ice hydrology, biomass burning, environmental hazards, satellite simulation and calibration, commercial applications, spectral algorithms, human infrastructure, as well as spectral modeling.

Invasive plants transform the three-dimensional structure of rain forests

Biological invasions contribute to global environmental change, but the dynamics and consequences of most invasions are difficult to assess at regional scales. We deployed an airborne remote sensing system that mapped the location and impacts of five highly invasive plant species across 221,875 ha of Hawaiian ecosystems, identifying four distinct ways that these species transform the three-dimensional (3D) structure of native rain forests. In lowland to montane forests, three invasive tree species replace native midcanopy and understory plants, whereas one understory invader excludes native species at the ground level. A fifth invasive nitrogen-fixing tree, in combination with a midcanopy alien tree, replaces native plants at all canopy levels in lowland forests. We conclude that this diverse array of alien plant species, each representing a different growth form or functional type, is changing the fundamental 3D structure of native Hawaiian rain forests. Our work also demonstrates how an airborne mapping strategy can identify and track the spread of certain invasive plant species, determine ecological consequences of their proliferation, and provide detailed geographic information to conservation and management efforts.

The Airborne Multi-angle Imaging SpectroRadiometer (AirMISR): instrument description and first results

An Airborne Multi-angle Imaging SpectroRadiometer (AirMISR) instrument has been developed to assist in validation of the Earth Observing System (EOS) MISR experiment. Unlike the EOS MISR, which contains nine individual cameras pointed at discrete look angles, AirMISR utilizes a single camera in a pivoting gimbal mount. The AirMISR camera has been fabricated from MISR brassboard and engineering model components and, thus, has similar radiometric and spectral response as the MISR cameras. This paper provides a description of the AirMISR instrument and summarizes the results of engineering flights conducted during 1997.

Accuracy of the spectral and radiometric laboratory calibration of the Airborne Visible/Infrared Imaging Spectrometer

The laboratory procedures, algorithms, measurements, and uncertainties associated with generation of the spectral and radiometric calibration of data acquired by AVIRIS are described. AVIRIS is an airborne sensor that obtains high-spatial-resolution image data of the earth in 224 spectral channels in four spectrometers covering the range from 400 to 2450 nm. The spectral calibration of AVIRIS agrees with the in-flight data to within two nanometers, and the absolute radiometric calibration is consistent with the in-flight verification to 10 percent over the spectral range. In-flight radiometric stability as measured by five consecutive passes over the surface calibration site is reported to be between three and five percent.

Ultra‐High Optical Absorption Efficiency from the Ultraviolet to the Infrared Using Multi‐Walled Carbon Nanotube Ensembles

The optical absorption efficiencies of vertically aligned multi-walled (MW)-carbon nanotube (CNT) ensembles are characterized in the 350-7000 nm wavelength range where CNT site densities > 1 × 10(11) /cm(2) are achieved directly on metallic substrates. The site density directly impacts the optical absorption characteristics, and while high-density arrays of CNTs on electrically insulating and non-metallic substrates have been commonly reported, achieving high site-densities on metals has been challenging and remains an area of active research. These absorber ensembles are ultra-thin (<10 μm) and yet they still exhibit a reflectance as low as ∼0.02%, which is 100 times lower than the reference; these characteristics make them potentially attractive for high-sensitivity and high-speed thermal detectors. In addition, the use of a plasma-enhanced chemical vapor deposition process for the synthesis of the absorbers increases the portfolio of materials that can be integrated with such absorbers due to the potential for reduced synthesis temperatures. The remarkable ruggedness of the absorbers is also demonstrated as they are exposed to high temperatures in an oxidizing ambient environment, making them well-suited for extreme thermal environments encountered in the field, potentially for solar cell applications. Finally, a phenomenological model enables the determinatiom of the extinction coefficients in these nanostructures and the results compare well with experiment.

Imaging spectrometer science measurements for Terrestrial Ecology: AVIRIS and new developments

Contiguous spectral measurements in the image domain made by the NASA Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) have been used to advance a range of Terrestrial Ecology science investigation over the past two decades. Currently there are hundreds of relevant refereed journal articles. The calibrated, high signal-to-noise ratio measurements of AVIRIS are used to investigate terrestrial ecology topics related to: (1) Pattern and Spatial Distribution of Ecosystems and their Components, (2) Ecosystem Function, Physiology and Seasonal Activity, (3) Biogeochemical Cycles, (3) Changes in Disturbance Activity, and (4) Ecosystems and Human Health.

Current instrument status of the airborne visible/infrared imaging spectrometer (AVIRIS)

An upgraded version of AVIRIS, an airborne imaging spectrometer based on a whiskbroom-type scanner coupled via optical fibers to four dispersive spectrometers, that has been in operation since 1987 is described. Emphasis is placed on specific AVIRIS subsystems including foreoptics, fiber optics, and an in-flight reference source; spectrometers and detector dewars; a scan drive mechanism; a signal chain; digital electronics; a tape recorder; calibration systems; and ground support requirements.

Advances in airborne remote sensing of ecosystem processes and properties: toward high-quality measurement on a global scale

Airborne remote sensing provides the opportunity to quantitatively measure biochemical and biophysical properties of vegetation at regional scales, therefore complementing surface and satellite measurements. Next-generation programs are poised to advance ecological research and monitoring in the United States, the tropical regions of the globe, and to support future satellite missions. The Carnegie Institution will integrate a next generation imaging spectrometer with a waveform LiDAR into the Airborne Taxonomic Mapping System (AToMS) to identify the chemical, structural and taxonomic makeup of tropical forests at an unprecedented scale and detail. The NEON Airborne Observation Platform (AOP) is under development with similar technologies with a goal to provide long-term measurements of ecosystems across North America. The NASA Next Generation Airborne Visible/Infrared Imaging Spectrometer (AVIRISng) is also under development to address the science measurement requirements for both the NASA Earth Science Research and Analysis Program and the spaceborne NASA HyspIRI Mission. Carnegie AToMS, NEON AOP, and AVIRISng are being built by the Jet Propulsion Laboratory as a suite of instruments. We discuss the synergy between these programs and anticipated benefits to ecologists and decision-makers.

Airborne visible/infrared imaging spectrometer (AVIRIS): recent improvements to the sensor and data facility

AVIRIS operations at the Jet Propulsion Laboratory consist primarily of a sensor task and a data facility task. These two activities are supported by an experiment coordination, a calibration and a management effort. The sensor task is responsible for AVIRIS sensor maintenance, laboratory calibration, and field operations. The AVIRIS data facility is responsible for data archiving, data calibration, quality monitoring and distribution. In this paper we describe recent improvements in these two primary AVIRIS tasks. The inflight performance of AVIRIS in 1992 and 1993 that resulted from these improvements is also presented.

The Airborne Methane Plume Spectrometer (AMPS): Quantitative imaging of methane plumes in real time

The Airborne Methane Plume Spectrometer (AMPS) is a mature instrument concept that is ready for development at the Jet Propulsion Laboratory (JPL). At its core is a novel high-resolution imaging spectrometer that records solar reflected light between 1.99 and 2.42 pm at 1 nm resolution, including strong methane (CH4) bands in the short-wave infrared. The push-broom spectrometer will leverage recent advancements in grating design and large-format 2D focal plane arrays to enable - for the first time - the high spectral resolution necessary for trace gas retrievals combined with high-performance imaging capabilities developed for surface remote sensing. AMPS features a 36° field of view with 600 resolved spatial elements across track (1 mRad) and 431 pixels in the spectral dimension. All other aspects of the instrument, such as the telescope, cryo-cooler, image stabilizer, GPS, are identical to available airborne JPL spectrometers in operation. The AMPS design is based on the next generation Airborne Visible Infrared Imaging Spectrometer (AVIRIS-NG), which has been used for high resolution mapping of CH4 concentrations from a controlled release experiment [1] and over existing natural gas fields [2]. A real time CH4 plume detection capability originally developed for AVIRIS-NG and successfully demonstrated over oil fields [3] will also be implemented with AMPS. This will facilitate surveys over existing oil and gas fields to identify and attribute CH4 emissions to individual point source locations, permit adaptive surveys with repeat imaging of suspected sources, and allow real time communication to site operators or ground crews equipped with additional instruments to verify observed plumes. AMPS will enable quantitative imaging of CH4 plumes at unprecedented spatial resolution and precision. Using a slow moving platform such as a helicopter at 100 m flight altitude (60 m image swath) will permit imaging CH4 enhancements at 10 cm spatial resolution and an unprecedented accuracy of 0.05 g CH4/m2. This will allow robust detection of CH4 emissions as low as 0.17 m3/h (6 standard cubic feet per hour), an order of magnitude smaller than what current airborne systems can detect. Using fixed-wing aircraft, AMPS can also be flown faster and higher (1 to 8 km flight altitude), thereby providing larger image swaths (0.6 to 4.8 km swaths respectively) and effective large scale surveys. Mapping CH4 emissions to individual point source locations could allow site operators to identify and mitigate these emissions, which reflect both a potential safety hazard and lost revenue. For the regulatory and scientific communities, understanding the distribution (spatial, temporal) and size of these emissions is of interest given the large uncertainties associated with anthropogenic emissions, including industrial point source emissions and fugitive CH4 from oil and gas infrastructure.