APEX - the Hyperspectral ESA Airborne Prism Experiment

Itten, K.I.; Dell'Endice, F.; Hueni, Andreas; Kneubühler, Mathias; Schläpfer, Daniel; Odermatt, Daniel; Seidel, F. C.; Huber, Silvia; Schopfer, Jürg; Kellenberger, Tobias; Bühler, Yves; D’Odorico, Petra; Nieke, Jens; Alberti, E.; Meuleman, Koen

doi:10.3390/s8106235

Cited by 101 publications

(62 citation statements)

References 54 publications

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“…Such data is only acquired on campaign basis from instruments such as APEX (Itten et al, 2008) or HySpex (Baumgartner et al, 2012). Since the surface reflectance has a large impact on the AMF, cf.…”

Section: Aerosol Profile and Propertiesmentioning

confidence: 99%

High-resolution airborne imaging DOAS measurements of NO<sub>2</sub> above Bucharest during AROMAT

Meier¹,

Schönhardt²,

Bösch³

et al. 2017

Atmos. Meas. Tech.

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Abstract. In this study we report on airborne imaging DOAS measurements of NO 2 from two flights performed in Bucharest during the AROMAT campaign (Airborne ROmanian Measurements of Aerosols and Trace gases) in September 2014. These measurements were performed with the Airborne imaging Differential Optical Absorption Spectroscopy (DOAS) instrument for Measurements of Atmospheric Pollution (AirMAP) and provide nearly gapless maps of column densities of NO 2 below the aircraft with a high spatial resolution of better than 100 m. The air mass factors, which are needed to convert the measured differential slant column densities (dSCDs) to vertical column densities (VCDs), have a strong dependence on the surface reflectance, which has to be accounted for in the retrieval. This is especially important for measurements above urban areas, where the surface properties vary strongly. As the instrument is not radiometrically calibrated, we have developed a method to derive the surface reflectance from intensities measured by AirMAP. This method is based on radiative transfer calculation with SCIATRAN and a reference area for which the surface reflectance is known. While surface properties are clearly apparent in the NO 2 dSCD results, this effect is successfully corrected for in the VCD results. Furthermore, we investigate the influence of aerosols on the retrieval for a variety of aerosol profiles that were measured in the context of the AROMAT campaigns. The results of two research flights are presented, which reveal distinct horizontal distribution patterns and strong spatial gradients of NO 2 across the city. Pollution levels range from background values in the outskirts located upwind of the city to about 4 × 10 16 molec cm −2 in the polluted city center. Validation against two co-located mobile car-DOAS measurements yields good agreement between the datasets, with correlation coefficients of R = 0.94 and R = 0.85, respectively. Estimations on the NO x emission rate of Bucharest for the two flights yield emission rates of 15.1 ± 9.4 and 13.6 ± 8.4 mol s −1 , respectively.

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Section: Aerosol Profile and Propertiesmentioning

confidence: 99%

High-resolution airborne imaging DOAS measurements of NO<sub>2</sub> above Bucharest during AROMAT

Meier¹,

Schönhardt²,

Bösch³

et al. 2017

Atmos. Meas. Tech.

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“…In particular, the Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) [26,27], designed and operated by the NASA Jet Propulsion Laboratory in California, has been used since the late 1980s in a large number of imaging spectroscopy experiments and field campaigns. Other airborne imaging spectrometers widely used in the last few years are HyMAP [28], the Compact Airborne Spectrographic Imager (CASI) [29] and the Airborne Prism Experiment (APEX) [30,31].…”

Section: Introductionmentioning

confidence: 99%

The EnMAP Spaceborne Imaging Spectroscopy Mission for Earth Observation

et al. 2015

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Imaging spectroscopy, also known as hyperspectral remote sensing, is based on the characterization of Earth surface materials and processes through spectrally-resolved measurements of the light interacting with matter. The potential of imaging spectroscopy for Earth remote sensing has been demonstrated since the 1980s. However, most of the developments and applications in imaging spectroscopy have largely relied on airborne spectrometers, as the amount and quality of space-based imaging spectroscopy data remain relatively low to date. The upcoming Environmental Mapping and Analysis Program (EnMAP) German imaging spectroscopy mission is intended to fill this gap. An overview of the main characteristics and current status of the mission is provided in this contribution. The core payload of EnMAP consists of a dual-spectrometer instrument measuring in the optical spectral range between 420 and 2450 nm with a spectral sampling distance varying between 5 and 12 nm and a reference signal-to-noise ratio of 400:1 in the visible and near-infrared and 180:1 in the shortwave-infrared parts of the spectrum. EnMAP images will cover a 30 km-wide area in the across-track direction with a ground sampling distance of 30 m. An across-track tilted observation capability will enable a target revisit time of up to four days at the Equator and better at high latitudes. EnMAP will contribute to the development and exploitation of spaceborne imaging spectroscopy applications by making high-quality data freely available to scientific users worldwide.

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“…Such viable a priori information will most certainly further improve estimation accuracy. Nevertheless, the automated CRASh approach as presented in this study showed the potential of a fully automated, image based retrieval of vital agroecosystem variables, and could be an important contribution towards the incorporation of land surface products in operational chains for upcoming high resolution airborne and spaceborne imaging spectrometers such as APEX [64], ARES [65,66], and EnMap [67]. [85] L = 0.5 [14]; a = 1.2 [14,55]; b = 0.04 [14]; X=0.08 [14]; β = 1 [86] …”

Section: Discussionmentioning

confidence: 99%

Enhanced Automated Canopy Characterization from Hyperspectral Data by a Novel Two Step Radiative Transfer Model Inversion Approach

Dorigo

Richter

Baret³

et al. 2009

Remote Sensing

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Automated, image based methods for the retrieval of vegetation biophysical and biochemical variables are often hampered by the lack of a priori knowledge about land cover and phenology, which makes the retrieval a highly underdetermined problem. This study addresses this problem by presenting a novel approach, called CRASh, for the concurrent retrieval of leaf area index, leaf chlorophyll content, leaf water content and leaf dry matter content from high resolution solar reflective earth observation data. CRASh, which is based on the inversion of the combined PROSPECT+SAILh radiative transfer model (RTM), explores the benefits of combining semi-empirical and physically based approaches. The approach exploits novel ways to address the underdetermined problem in the context of an automated retrieval from mono-temporal high resolution data. To regularize the inverse problem in the variable domain, RTM inversion is coupled with an OPEN ACCESSRemote Sens. 2009, 1 1140 automated land cover classification. Model inversion is based on a two step lookup table (LUT) approach: First, a range of possible solutions is selected from a previously calculated LUT based on the analogy between measured and simulated reflectance. The final solution is determined from this subset by minimizing the difference between the variables used to simulate the spectra contained in the reduced LUT and a first guess of the solution. This first guess of the variables is derived from predictive semi-empirical relationships between classical vegetation indices and the single variables. Additional spectral regularization is obtained by the use of hyperspectral data. Results show that estimates obtained with CRASh are significantly more accurate than those obtained with a tested conventional RTM inversion and semi-empirical approach. Accuracies obtained in this study are comparable to the results obtained by various authors for better constrained inversions that assume more a priori information. The completely automated and image-based nature of the approach facilitates its use in operational chains for upcoming high resolution airborne and spaceborne imaging spectrometers.

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APEX - the Hyperspectral ESA Airborne Prism Experiment

Cited by 101 publications

References 54 publications

High-resolution airborne imaging DOAS measurements of NO<sub>2</sub> above Bucharest during AROMAT

High-resolution airborne imaging DOAS measurements of NO<sub>2</sub> above Bucharest during AROMAT

The EnMAP Spaceborne Imaging Spectroscopy Mission for Earth Observation

Enhanced Automated Canopy Characterization from Hyperspectral Data by a Novel Two Step Radiative Transfer Model Inversion Approach

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APEX - the Hyperspectral ESA Airborne Prism Experiment

Cited by 101 publications

References 54 publications

High-resolution airborne imaging DOAS measurements of NO&lt;sub&gt;2&lt;/sub&gt; above Bucharest during AROMAT

High-resolution airborne imaging DOAS measurements of NO&lt;sub&gt;2&lt;/sub&gt; above Bucharest during AROMAT

The EnMAP Spaceborne Imaging Spectroscopy Mission for Earth Observation

Enhanced Automated Canopy Characterization from Hyperspectral Data by a Novel Two Step Radiative Transfer Model Inversion Approach

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Product

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About

High-resolution airborne imaging DOAS measurements of NO<sub>2</sub> above Bucharest during AROMAT

High-resolution airborne imaging DOAS measurements of NO<sub>2</sub> above Bucharest during AROMAT