Kerry N. Buckland

MAGI: A New High-Performance Airborne Thermal-Infrared Imaging Spectrometer for Earth Science Applications

A new airborne facility instrument for Earth science applications is introduced. The Mineral and Gas Identifier (MAGI) is a wide-swath (programmable up to ±42° off nadir) moderate spectral resolution thermal-infrared (TIR) imaging spectrometer that spans the 7.1- to 12.7-μm spectral window in 32 uniform and contiguous channels. Its spectral resolution enables improved discrimination of rock and mineral types, greatly expanded gas-detection capability, and generally more accurate land-surface temperature retrievals. The instrument design arose from trade studies between spectral resolution, spectral range, and instrument sensitivity and has now been validated by flight data acquired with the completed sensor. It offers a potential prototype for future space-based TIR instruments, which will require much higher spectral resolution than is currently available in order to address more detailed climate, anthropogenic, and solid Earth science questions.

Comparing imaging spectroscopy and in situ observations of Chino dairy complex emissions

Methane, CH4, and ammonia, NH3, directly and indirectly influence the atmospheric radiative balance. Long wave infrared (LWIR) airborne hyperspectral imagery and in situ data of CH<inf>4</inf>, CO<inf>2</inf>, and NH<inf>3</inf> plumes were collected from the Chino Dairy Complex in the Los Angeles Basin. LWIR data showed significant emissions heterogeneity between dairies with good spatial agreement with in situ measurements. Remote sensing data also showed topographic effects on plumes mapped for at least 19 km. Repeated in situ measurements showed that emissions were persistent on half-year timescales. Inversion of one dairy plume found annual emissions of 4.1×10⁵ kg CH<inf>4</inf>, 2.2×10⁵kg NH<inf>3</inf>, and 2.3×10⁷ kg CO<inf>2</inf>, suggesting 3500, 4000, and 2100 head of cattle, respectively. Far field data showed chemical conversion of Chino NH<inf>3</inf> occurs within the confines of the Los Angeles Basin on % day timescale, faster than previously published values.

Mako airborne thermal infrared imaging spectrometer: performance update

The Aerospace Corporation’s sensitive Mako thermal infrared imaging spectrometer, which operates between 7.6 and 13.2 microns at a spectral sampling of 44 nm, and flies in a DeHavilland DHC-6 Twin Otter, has undergone significant changes over the past year that have greatly increased its performance. A comprehensive overhaul of its electronics has enabled frame rates up to 3255 Hz and noise reductions bringing it close to background-limited. A replacement diffraction grating whose peak efficiency was tuned to shorter wavelength, coupled with new AR coatings on certain key optics, has improved the performance at the short wavelength end by a factor of 3, resulting in better sensitivity for methane detection, for example. The faster frame rate has expanded the variety of different scan schemes that are possible, including multi-look scans in which even sizeable target areas can be scanned multiple times during a single overpass. Off-nadir scanning to ±56.4° degrees has also been demonstrated, providing an area scan rate of 33 km2/minute for a 2-meter ground sampling distance (GSD) at nadir. The sensor achieves a Noise Equivalent Spectral Radiance (NESR) of better than 0.6 microflicks (μf, 10-6 W/sr/cm2/μm) in each of the 128 spectral channels for a typical airborne dataset in which 4 frames are co-added. An additional improvement is the integration of a new commercial 3D stabilization mount which is significantly better at compensating for aircraft motions and thereby maintains scan performance under quite turbulent flying conditions. The new sensor performance and capabilities are illustrated.

Remote sensing visualization and quantification of ammonia emission from an inland seabird colony

Abstract Remote sensing measurements of ammonia emitted by a near-monotypic seabird colony established on an islet in the Salton Sea (Imperial Valley, California) are described. The compact (3 ha) nature of the island affords a constrained environment that provides an ideal case study for validating models of ammonia emission from seabird colonies. Incorporated as part of a coordinated approach to future field campaigns, the techniques demonstrated would provide a means for validation and refinement of current seabird ammonia emission models on a case study basis. This would contribute to an improved understanding of the nitrogen cycle, especially in remote ocean locales.

Mapping Refrigerant Gases in the New York City Skyline

Cities are now home to more than 50% of the world’s population and emit large quantities of pollutants from sources such as fossil fuel combustion and the leakage of refrigerants. We demonstrate the utility of persistent synoptic longwave hyperspectral imaging to study the ongoing leakage of refrigerant gases in New York City, compounds that either deplete the stratosphere ozone or have significant global warming potential. In contrast to current monitoring programs that are based on country-level reporting or aggregate measures of emissions, we present the identification of gaseous plumes with high spatial and temporal granularity in real-time over the skyline of Manhattan. The reported data highlights the emission of chemicals scheduled for phase-out. Our goal is to contribute to better understanding of the composition, sources, concentration, prevalence and patterns of emissions for the purposes of both research and policy.

Urban-industrial emissions monitoring with airborne longwave-infrared hyperspectral imaging

The advantages of airborne hyperspectral longwave-infrared imaging for emissions monitoring are described in the context of urban-industrial environments. These benefits are illustrated by means of several case studies.

Multi-year study of remotely-sensed ammonia emission from fumaroles in the salton sea geothermal field

A multi-year study of ammonia emissions from a recently exposed geothermal fumarole field at the SE edge of the Salton Sea (Southern California) is described. The work makes extensive use of airborne thermal-infrared hyperspectral imagery acquired over the field site.

Geologic swath map of the lavic lake fault from airborne thermal hyperspectral imagery

The 1999 Hector Mine earthquake on the Lavic Lake fault produced a maximum right-lateral displacement of ∼5 m, but the long-term cumulative offset remains unresolved. To identify bedrock that has been offset by the fault, we produced a swath map from airborne hyperspectral imagery. High spatial and spectral resolution, along with a lack of significant vegetation cover helped us differentiate lithologic units and create a geologic map with supervised and unsupervised classifications. Supervised classifications over a small test site had an overall accuracy of 71 ± 1%, and some of the boundaries between units in our unsupervised classification correlate well with lithologic boundaries from a previously published geologic map that covers the same area. Our geologic fault swath map will help to resolve the total tectonic offset of bedrock along the Lavic Lake fault.

Hyperspectral LWIR mapping of fumarole sulfates, salton sea, imperial county, California

Several ammonia emitting fumarole fields have recently been exposed along the southeastern shoreline of the Salton Sea in Imperial County, California. A complex assemblage of sulfate minerals, many containing ammonium ion, are associated with the fumaroles. The distribution of these sulfates was mapped by remote sensing with the Mako LWIR hyperspectral sensor. The most common minerals tended to form somewhat concentric discontinuous rings. Outwardly from the central fumarole vent, they were: mascagnite/boussingaultite, gypsum, nitratine and bloedite, respectively. Ground truth surveys coupled with laboratory analyses were generally in good agreement with the remote sensing results.

High areal rate longwave-infrared hyperspectral imaging for environmental remote sensing

The Mako airborne longwave-infrared hyperspectral sensor is a whiskbroom imager operating in the 7.6-13.2 μm region with 44-nm spectral sampling and <30 mK noise-equivalent differential temperature (NEDT). It has undergone progressive development since its inaugural flights in 2010 and is capable of acquiring 112° swaths with an areal rate of 33 km2 min-1 at 2-m ground sampling distance. The sensor performance envelope allows for a number of operational modes that can be deployed against a variety of acquisition scenarios. Its suitability for environmental remote sensing applications is illustrated with reference to a number of representative case studies drawn from several years of airborne collections within the Los Angeles Basin and beyond.