-
A. Hueni,
J. Biesemans,
K. Meuleman,
F. Dell'Endice,
D. Schlapfer,
D. Odermatt,
M. Kneubuehler,
S. Adriaensen,
S. Kempenaers,
J. Nieke, K.I. Itten
[show abstract]
[hide abstract]
ABSTRACT: The product generation from hyperspectral sensor data has high requirements on the processing infrastructure, both hardware and software. The Airborne Prism Experiment (APEX) processing and archiving facility has been set up to provide for the automated generation of level-1 calibrated data and user-configurable on-demand product generation for higher processing levels. The system offers full reproducibility of user orders and processing parameters by employing a relational database. The flexible workflow software allows for the quick integration of novel algorithms or the definition of new processing sequences. Reprocessing of data is supported by the archiving approach. Configuration management based on the database enables the control over different versions of processing modules to be applied. The system is described with a focus on the APEX instrument; however, its generic design allows adaptation to other sensor systems.
IEEE Transactions on Geoscience and Remote Sensing 02/2009; · 2.89 Impact Factor
-
EARSeL SIG SI workshop: Imaging Spectroscopy, Tel Aviv, Israel; 01/2009
-
EARSeL SIG SI workshop: Imaging Spectroscopy, Tel Aviv, Israel; 01/2009
-
[show abstract]
[hide abstract]
ABSTRACT: The increasing quantity and sophistication of imaging spectroscopy applications have led to a higher demand on the quality of Earth observation data products. In particular, it is desired that data products be as consistent as possible (i.e., ideally uniform) in both spectral and spatial dimensions. Yet, data acquired from real (e.g., pushbroom) imaging spectrometers are adversely affected by various categories of artifacts and aberrations including as follows: singular and linear (e.g., bad pixels and missing lines), area (e.g., optical aberrations), and stability and degradation defects. Typically, the consumer of such data products is not aware of the magnitude of such inherent data uncertainties even as more uncertainty is introduced during higher level processing for any particular application. In this paper, it is shown that the impact of imaging spectrometry data product imperfections in currently available data products has an inherent uncertainty of 10%, even though worst case scenarios were excluded, state-of-the-art corrections were applied, and radiometric calibration uncertainties were excluded. Thereafter, it is demonstrated how this error can be reduced (<5%) with appropriate available technology (onboard, scene, and laboratory calibration) and assimilation procedures during the preprocessing of the data. As a result, more accurate, i.e., uniform, imaging spectrometry data can be delivered to the user community. Hence, the term uniformity of imaging spectrometry data products is defined for enabling the quantitative means to assess the quality of imaging spectrometry data. It is argued that such rigor is necessary for calculating the error propagation of respective higher level processing results and products.
IEEE Transactions on Geoscience and Remote Sensing 11/2008; · 2.89 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: The facilities to support the ESA's airborne APEX hyperspectral mission simulator are described. These facilities include calibration tools, such as specific processing in a dedicated Processing and Archiving Facility (PAF), operational calibration and characterization using the Calibration Home Base (CHB), the In-Flight Characterization facility (IFC) and the Calibration Test Master (CTM). Further on, a preview on major applications and the corresponding development efforts to provide scientific data products up to level 2/3 to the user are outlined. Products dedicated for the retrieval of limnology, vegetation, atmospheric parameters, as well as general classification routines and rapid mapping tasks are currently under development and prepared for dissemination by the APEX Science Center (ASC) and the APEX Operations Center (AOC).
Geoscience and Remote Sensing Symposium, 2008. IGARSS 2008. IEEE International; 08/2008
-
[show abstract]
[hide abstract]
ABSTRACT: The facilities to support the ESA’s airborne APEX hyperspectral mission simulator are described. These facilities include calibration tools, such as specific processing in a dedicated Processing and Archiving Facility (PAF), operational calibration and characterization using the Calibration Home Base (CHB), the In-Flight Characterization facility (IFC) and the Calibration Test Master (CTM). Further on, a preview on major applications and the corresponding development efforts to provide scientific data products up to level 2/3 to the user are outlined. Products dedicated for the retrieval of limnology, vegetation, atmospheric parameters, as well as general classification routines and rapid mapping tasks are currently under development and prepared for dissemination by the APEX Science Center (ASC) and the APEX Operations Center (AOC).
2008 IEEE International Geoscience & Remote Sensing Symposium; 01/2008
-
K. I. Itten,
F. Dell'Endice,
A. Hueni,
M. Kneubuhler,
D. Schlaper,
D. Odermatt,
F. Seidel,
S. Huber,
J. Schopfer,
T. Kellenberger,
Y. Bühler,
P. D'Odorico,
J. Nieke,
E. Alberti,
K Meuleman
Sensors 01/2008; 8:6235-6259. · 1.74 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Efficient and accurate imaging spectroscopy data processing asks for perfectly consistent (i.e., ideally uniform) data in both the spectral and spatial dimensions. However, real pushbroom-type imaging spectrometers are affected by various point spread function (PSF) nonuniformity artifacts. First, individual pixels or lines may be missing in the raw data due to bad pixels originating from the detector, readout errors, or even electronic failures. Second, so-called smile and keystone optical aberrations are inherent to imaging spectrometers. Appropriate resampling strategies are required for the preprocessing of such data if emphasis is put on spatial PSF uniformity. So far, nearest neighbor interpolations have been often recommended and used for resampling. This paper shall analyze the radiometric effects if linear interpolation is used to optimize the spatial PSF uniformity. For modeling interpolation effects, an extensive library of measured surface reflectance spectra as well as real imaging spectroscopy data over various land cover types are used. The real measurements are systematically replaced by interpolated values, and the deviation between original and resampled spectra is taken as a quality measure. The effects of nearest neighbor resampling and linear interpolation methods are compared. It is found that linear interpolation methods lead to average radiometric errors below 2% for the correction of spatial PSF nonuniformity in the subpixel domain, whereas the replacement of missing pixels leads to average errors in the range of 10%-20%
IEEE Transactions on Geoscience and Remote Sensing 03/2007; · 2.89 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: An aerosol retrieval algorithm is currently under development in scope of the upcoming APEX hyperspectral imager. It will be able to close the gap between global remote sensing and one-dimensional in situ measurements of atmospheric particles. This paper presents a feasibility study of the proposed APEX aerosol retrieval approach for hyperspectral imagery with high spatial resolution. The extraction of a sample aerosol optical thickness is done by fitting radiation transfer model results to measured at-sensor radiances at two near-UV/blue bands (394 and 404 nm) from the PHILLS imager. The PHILLS hyperspectral data are used to simulate the APEX Visible Near- Infrared detector and comprehend a dark surface reference target to avoid most uncertainties from the surface reflection contribution.
Geoscience and Remote Sensing Symposium, 2006. IGARSS 2006. IEEE International Conference on; 09/2006
-
[show abstract]
[hide abstract]
ABSTRACT: Scene-based spectrometer calibration is becoming increasingly interesting due to the decreasing cost of computing resources as compared with laboratory calibration costs. Three of the most important instrument parameters needed for deriving surface reflectance products are per-band bandwidths, i.e., full-width at half-maximum, band centers, and spectral response function (SRF) shape. Methods for scene-based bandwidth and band center retrieval based on curve matching in the spectral regions near well-known solar and atmospheric absorption features have been investigated with satisfying results. The goal of this work is to establish the feasibility of per-band SRF shape discernibility. To this end, at-sensor radiances in multiple application configurations have been modeled using Moderate-Resolution Atmospheric Transmission (MODTRAN) 4 configured for the currently being built Airborne Prism Experiment (APEX) imaging spectrometer in its unbinned configuration (i.e., optimized for spectral resolution). To establish SRF shape discernment feasibility, per-band MODTRAN 4 spectral "filter response function" files have been generated for five common theoretical shapes using APEX nominal bandwidth and band center specifications and are provided as MODTRAN 4 input for the instrument model. In several application configurations, the typically used Gaussian SRF is used as reference and compared with radiances resulting from hypothetical instruments based on the four other shapes to detect differences in selected spectral subsets or "windows" near well-known Fraunhofer features. A relative root-mean-square metric is used to show that discernment in some cases is directly feasible, and in others, feasible if noise reduction techniques (e.g., along-track averaging of homogeneous targets) are possible
IEEE Geoscience and Remote Sensing Letters 08/2006; · 1.56 Impact Factor
-
01/2006: pages 391-400;
-
[show abstract]
[hide abstract]
ABSTRACT: Field and laboratory goniometers are widely used in the remote sensing community to assess spectrodirectional reflection properties of selected targets. Even when the same target and goniometer system are used, field and laboratory results cannot directly be compared due to inherent differences, mainly in the illumination conditions since actual goniometers measure a hemispherical-conical reflectance in the field and a biconical reflectance in the lab. Yet, the ability to compare and combine measurements from different instrumental designs is critical to ensure sensor cross-calibration and for all applications that rely on measurements obtained with both types of instruments. One approach to this problem consists in retrieving the bidirectional reflectance distribution function (BRDF) of the targets of interest for each experimental setup and to compare these, since theoretically they are independent of the particular conditions of illumination and observation. This involves a correction for diffuse incoming radiation in the case of field measurements, and a correction for conicity and inhomogeneity of illumination in the case of laboratory measurements. In this paper, we present a novel BRDF retrieval scheme for typical laboratory goniometers and compare it with the usual correction method assuming Lambertian behavior. We then discuss the first results of measurements and BRDF retrievals using the field and laboratory goniometer systems of the Remote Sensing Laboratories of the University of Zurich, which share the exact observation geometry, on the same inert, highly anisotropic target.
IEEE Transactions on Geoscience and Remote Sensing 12/2005; · 2.89 Impact Factor
-
13th Annual JPL Airborne Earth Science Workshop13th Annual JPL Airborne Earth Science Workshop, Pasadena; 01/2004
-
International Radiation Symposium, Busan, Korea, 23-28 August 2004International Radiation Symposium, Busan, Korea, 23-28 August 2004, Busan, Korea; 01/2004
-
M.E. Schaepman, K.I. Itten,
D. Schlapfer,
J.W. Kaiser,
J. Brazile,
W. Debruyn,
A. Neukom,
H. Feusi,
P. Adolph,
R. Moser,
T. Schilliger,
L. De Vos,
G. Brandt,
P. Kohler,
M. Meng,
J. Piesbergen,
P. Strobl,
J. Gavira,
G. Ulbrich,
R. Meynart
[show abstract]
[hide abstract]
ABSTRACT: Over the past few years, a joint Swiss/Belgian initiative resulted in a project to build a new generation airborne imaging spectrometer, namely APEX (Airborne Prism Experiment) under the ESA funding scheme named PRODEX. APEX is designed to be a dispersive pushbroom imaging spectrometer operating in the solar reflected wavelength range between 400 and 2500 nm. The spectral resolution is designed to be better than 10 nm in the SWIR and 5 nm in VIS/NIR range of the spectrum. The total FOV is on the order of ±14°, recording 1000 pixels across track, and max. 300 spectral bands simultaneously. The final radiance data products are well characterized and calibrated to be traceable to absolute standards. APEX is subdivided into an industrial team responsible for the optical instrument, the calibration home base, and the detectors, and a science and operational team, responsible for the processing and archiving of the imaging spectrometer data, as well as its operation. APEX is in its design phase with partial breadboarding activities and will be operationally available to the user community in the year 2005.
Geoscience and Remote Sensing Symposium, 2003. IGARSS '03. Proceedings. 2003 IEEE International; 08/2003
-
[show abstract]
[hide abstract]
ABSTRACT: Field goniometer measurements are a tool to generate a priori bidirectional reflectance distribution function (BRDF) knowledge for correction and validation of directional reflectance data acquired by air- and spaceborne sensors. This study analyzes the diurnal hemispherical-directional reflectance factor data of an alfalfa canopy measured during the Digital Airborne Imaging Spectrometer Experiment 1999 (DAISEX'99). We analyze the variation of measured and modeled spectrodirectional vegetation data, revealing that measurement noise is negligible compared to the variation due to the canopy's anisotropy. The deviations of the spectral albedo (bihemispherical reflectance) and of field spectrometer nadir measurements throughout a day prove to be larger than modeled deviations. Calculated anisotropy factors quantify the spectral-dependent effects of the vegetation reflectance anisotropy. This paper is a contribution toward the generation of a reliable BRDF database by suggesting methods to preprocess and analyze observed directional vegetation reflectance data, with special emphasis on the spectral dimension.
IEEE Transactions on Geoscience and Remote Sensing 06/2003; · 2.89 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Over the past few years, a joint Swiss/Belgium ESA initiative resulted
in a project to build a precursor mission of future spaceborne imaging
spectrometers, namely APEX (Airborne Prism Experiment). APEX is designed
to be an airborne dispersive pushbroom imaging spectrometer operating in
the solar reflected wavelength range between 400 and 2500 nm. The system
is optimized for land applications including limnology, snow, soil,
amongst others. The baseline for the requirements of APEX are built on
various land requirements and subsequently modelled to at-sensor
specific radiances. The model is based on existing biophysical and
-chemical retrieval algorithms and assumes no physical limitation of the
sensor system. Final technology limitations are discussed using system
tradeoffs. The absolute radiance calibration of APEX includes the use of
pre- and post-data acquisition internal calibration facility as well as
a laboratory calibration and a performance model serving as a stable
reference. We will discuss the instrument's present status in its
breadboarding phase, including some new results with respect to the
detector development and design optimization for imaging spectrometers.
In the same framework of APEX, a complete processing and archiving
facility (PAF) is developed. The PAF not only includes imaging
spectrometer data processing up to physical units, but also geometric
and atmospheric correction for each scene, as well as calibration data
input. The PAF software includes an Internet based web-server and
provides interfaces to data users as well as instrument operators and
programmers. The software design, the tools and its life cycle is
discussed as well. Further we will discuss particular instrument
requirements (resampling, bad pixel treatment, etc.) in view of the
operation of the PAF as well as their consequences on the product
quality. Finally we will discuss a combined approach for geometric and
atmospheric correction including BRDF (or view angle) related effects.
03/2003; -1:12386.
-
[show abstract]
[hide abstract]
ABSTRACT: Within the framework of the European Space Agency's funding scheme
PRODEX, an airborne imaging spectrometer named APEX (Airborne PRISM
Experiment) is developed. APEX is designed to be a pushbroom imager with
300 spectral channels in the 400-2500 nm wavelength region, and with
1000 pixels across track. The mission objectives of APEX are mainly
being a simulator, calibrator and validation experiment and fostering
the application development for hyperspectral imaging. The APEX hardware
consists of an airborne imaging spectrometer with an optimized
hyperspectral sensor design for the detection of land surface processes,
a flexible aircraft integration scheme, a laboratory calibration home
base, and a Processing and Archiving Facility (PAF) for the generation
of Level 1 through 3 data
Geoscience and Remote Sensing Symposium, 2000. Proceedings. IGARSS 2000. IEEE 2000 International; 02/2000
-
01/2000: pages 255; ESA/ESTEC 13115/98/NL/VJ(IC), Univ. Zurich.
-
[show abstract]
[hide abstract]
ABSTRACT: The development of the Airborne PRISM Experiment (APEX) has been supported by the European Space Agency (ESA) in view of an appropriate data simulator of the future LSPIM mission. The calibration of the APEX instrument will be performed using a standardized laboratory calibration procedure, where spectral response, geometric response, as well as gain and offset values will be determined. Additionally, an in-flight calibration consisting of built-in means and vicarious calibration approaches will be performed. All calibration related parameters are stored in a database for later reconstruction of the calibration process as well as for drift and trend analysis. A processing chain is defined for appropriate data preparation which allows an efficient generation of all the calibration parameters and a fast processing of all acquired data from raw format to calibrated radiances. Sensor simulation, standard quality control procedures, and in-flight validation campaigns finally give a characterization of the accuracy of the calibration, its trends, and the reliability of the delivered image data products. 1.0
04/1999;
