Design and prototyping of the SPECTRA simulator architecture

SPECTRA (Surface Processes and Ecosystem Changes through Response Analysis) is a planned spaceborne multiangular hyperspectral and thermal imaging spectrometer in phase A early design led by ESA's earth observation group. Its mission is to describe, understand and model the role of terrestrial vegetation in the global carbon cycle and its response to climate variability. Even though the project has been terminated in November 2005, many results of the phase A studies are considered to be useful as input to future missions. The SPECTRA end-to-end simulator is intended to be used to test different aspects of the SPECTRA mission concept and for tuning the retrieval algorithms as well as assessing their performances. The intention of this ESA-commissioned study was not to build an actually working simulator, but to conceive an architecture for a simulator to be built during phase B of the SPECTRA design, as well as perform a limited validation of this architecture. The software architecture for the future SPECTRA end-to-end simulator has been designed to be modular, flexible and distributed. It consists of a central control unit with associated database, which is controlled and monitored via an internet-accessible web interface, and a flexible number of modules performing the actual calculations. The list of simulator modules currently includes but is not limited to state-of-the-art developments in radiative transfer (Onera), instrument modelling (ESA), atmospheric correction (Onera), and various level 2 algorithms (Alterra). Assimilation models and global carbon flux models are linked to the simulator via the SPECTRA field segment database (RSL and Princeton), for which a high level schema has been defined. The simulator structure has been validated using full end-to-end simulations from ground data to top-of-atmosphere, through the SPECTRA instrument simulator provided by industry, and back again. Test data from the Barrax field site are used for this purpose (University of Valencia)

APEX: Current Status of the Airborne Dispersive Pushbroom Imaging Spectrometer

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, and soil, amongst others. The instrument is optimized with various steps taken to allow for absolute calibrated radiance measurements. This includes the use of a pre-and post-data acquisition internal calibration facility as well as a laboratory calibration and a performance model serving as a stable reference. The instrument is currently in its breadboarding phase, including some new results with respect to detector development and design optimization for imaging spectrometers. In the same APEX framework, 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 are discussed as well

APEX: Current Status of the Airborne Dispersive Pushbroom Imaging Spectrometer

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, and soil, amongst others. The instrument is optimized with various steps taken to allow for absolute calibrated radiance measurements. This includes the use of a pre-and post-data acquisition internal calibration facility as well as a laboratory calibration and a performance model serving as a stable reference. The instrument is currently in its breadboarding phase, including some new results with respect to detector development and design optimization for imaging spectrometers. In the same APEX framework, 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 are discussed as well

Using learning management systems as support mechanisms for formative feedback – the case of lifelong learning.

For several years Learning Management Systems and e-portfolios have been used in conjunction to Virtual Learning Environments to provide additional means for education support. The field of e-learning has an impressive literature focusing on tools that support teaching, learning and assessment activities. The missing element for several years has been providing an integrated approach dealing with issues relating to pedagogy, technology and learning. The design and delivery of formative assessment opportunities has been the focus of the author’s research for several years, in conjunction to emphasis on how formative feedback can be supported in e-learning scenarios. For more than ten years several case studies have been investigated with respect to how feedback is perceived in distance education and the identification of key differences between instructors and learners. This paper discusses the above issues with the aid of lifelong learning scenarios. Emphasis is given on presenting tools that have been developed to support the entire learning process from its early curriculum design stages to the delivery of specific feedback on various learning activities. The main contribution of the paper is through a framework for providing customised and personalised feedback based on a semi-automated mechanism supported by learning management systems. Evaluation results from pilot studies and cooperative evaluation with a number of student participants are presented and reflected on in the paper

Characterisation of the mechanical properties of infarcted myocardium in the rat under biaxial tension and uniaxial compression

Understanding the passive mechanical properties of infarcted tissue at different healing stages is essential to explore the emerging biomaterial injection-based therapy for myocardial infarction (MI). Although rats have been widely used as animal models in such investigations, the data in literature that quantify the passive mechanical properties of rat heart infarcts is very limited. MI was induced in rats and hearts were harvested immediately (0 day), 7, 14 and 28 days after infarction onset. Left ventricle anterioapical samples were cut and underwent equibiaxial and non equibiaxial tension followed by uniaxial compression mechanical tests. Histological analysis was conducted to confirm MI and to quantify the size of the induced infarcts. Infarcts maintained anisotropy and the nonlinear biaxial and compressive mechanical behaviour throughout the healing phases with the circumferential direction being stiffer than the longitudinal direction. Mechanical coupling was observed between the two axes in all infarct groups. The 0, 7, 14 and 28 days infarcts showed 438, 693, 1048 and 1218 kPa circumferential tensile moduli. The 28 day infarct group showed a significantly higher compressive modulus compared to the other infarct groups (p=0.0060, 0.0293, and 0.0268 for 0, 7 and 14 days groups). Collagen fibres were found to align in a preferred direction for all infarct groups supporting the observed mechanical anisotropy. The presented data are useful for developing material models for healing infarcts and for setting a baseline for future assessment of emerging mechanical-based MI therapies