Toward optical signal processing using photonic reservoir computing

We propose photonic reservoir computing as a new approach to optical signal processing in the context of large scale pattern recognition problems. Photonic reservoir computing is a photonic implementation of the recently proposed reservoir computing concept, where the dynamics of a network of nonlinear elements are exploited to perform general signal processing tasks. In our proposed photonic implementation, we employ a network of coupled Semiconductor Optical Amplifiers (SOA) as the basic building blocks for the reservoir. Although they differ in many key respects from traditional software-based hyperbolic tangent reservoirs, we show using simulations that such a photonic reservoir can outperform traditional reservoirs on a benchmark classification task. Moreover, a photonic implementation offers the promise of massively parallel information processing with low power and high speed. (C) 2008 Optical Society of America

PROBA-V successor phase 0 Final Report

The current PROBA-V system is a global land monitoring mission with the prime aim of achieving data continuity for the user of SPOT-VEGETATION data. PROBA-V has been launched on May 7th 2013, to continue the observation timeline of SPOT-VEGETATION. PROBA-V has experienced a quasi-perfection injection and will thus be in an acceptable orbit for its extended mission lifetime of 5 years. The expected mission lifetime thus expires by mid of 2018. Since the interest for global land monitoring is only expected to continue in the future, this study wants to define the mission requirements and possible mission scenarios for a follow-on mission. The goal of such a new PROBA-V mission is clear: it should ensure the data continuity of global vegetation monitoring, while taking the opportunity to further improve the data quality - provided the added value can be motivated. Data continuity is essential for understanding long term trends of land use that may affect the global equilibrium of the planet (in the context of scarcity for land or food, natural disasters, climate change). As for added value, a fine example is the improvement of spatial resolution when comparing PROBA-V with the spatial resolution in SPOT-VEGETATION products. Indeed, as will be shown in chapter 2, an improvement in spatial resolution towards a full 100m product is considered by the user community as the main target for a PROBA-V follow-on mission

A 100 M GROUND RESOLUTION GLOBAL DAILY COVERAGE EARTH OBSERVATION MISSION

PROBA-V has been successfully launched on 7th May 2013 and is providing a global monitoring in the continuity of the SPOT-VEGETATION mission. The progress in terms of ground resolution between Spot VGT and PROBA-V is a factor 3 (1 km to 1/3 km ground resolution product). The User Community requirements for the next generation of global monitoring are a 100 m ground resolution product. This means an additional factor 3 improvement, but in a short time frame (5 years). After success of the PROBA-V mission, the Belgian Science Policy (BELSPO) initiates a PROBA-V Successor feasibility study. This study was undertaken by VITO and CSL to identify potential tracks to achieve a follow-on mission which is expected to be relevant for the User Community. The mission analyses for each of these tracks was evaluated. Today the PROBA-V mission lifetime is expected to expire by mid of 2018. Since the interest for global land monitoring is expected to continue in the future, this study proposes mission requirements and a shortlist of optimal mission scenarios for a follow-on mission in this short time frame. The goal of such a new PROBA-V mission is clear: it should ensure the data continuity of global vegetation monitoring, while taking the opportunity to further improve the data quality. Data continuity is essential for understanding long term trends of land use that may affect the global equilibrium of the planet (in the context of scarcity for land or food, natural disasters, climate change). As for added value, a fine example is the improvement of spatial resolution when comparing PROBA-V with the spatial resolution in SPOT-VEGETATION products. An improvement in spatial resolution towards a full 100m product is considered by the user community as the main target for a PROBA-V follow-on mission

Comparaison entre les télescope hors axes de type TMA et FMA, optimisés sur différents champs de vue: application à l'observation de la terre

TMA, or three mirror anastigmats, have already been used successfully for various space missions. In the frame of earth observation, ProbaV satellite uses 3 TMAs to cover a total 102.4° field-of-view; ground sampling distance is about 100m at the center of field-of view and 370m at the edge. For future earth observation missions, the goal would be to reach 100m spatial resolution all over the 102.4° FOV. This would require to up-scale optical specifications, thus increasing geometrical aberrations. FMA, or four mirror anastigmats, could thus be a good candidate for future missions, as a fourth mirror would allow better correction of optical aberrations. In this work, TMA and FMA have been optimized over different fields-of view. Performance limitations are then derived, which show that FMA seems promising for future missions. Radiometry aspects are discussed and preliminary tolerance analysis is carried out.ProbaV Successo

PROBA-V Commissioning: Radiometric Calibration

The Belgian-ESA Proba-V(egetation) satellite is to be launched in April 2013. The aim of the Proba-V mission is to ensure data product continuity with SPOT-VEGETATION, which ends its operations in 2014. While developed in the frame of ESA’s In Orbit Demonstration (IOD) technological program, Proba-V is an operational mission providing the user community daily with global land coverage data in four multispectral bands at both 1/3 km and 1 km resolution. This user community requires reliable and consistent measurements over time in order to detect and quantify changes in the Earth’s environment. To this end, the radiometric calibration requirements for PROBA-V specify 5 % absolute and 3 % relative accuracies. To guarantee this high quality over the full lifetime of PROBA-V, in-flight calibration algorithms have to be in place which fully consider the specific properties of the PROBA-V platform and its instrument design characteristics. Due to size, weight and power constraints, no onboard calibration devices are available. Therefore the PROBA-V in-flight radiometric calibration has to rely solely on vicarious calibration methods. The radiometric calibration after launch will be performed by the PROBA-V Image Quality Center (IQC) located at VITO. To this end, VITO developed the Optical Sensor Calibration with simulated Radiance (OSCAR) facility. It will be used for the vicarious calibration activities of PROBA-V. OSCAR encompasses various calibration methods based on the exploitation of reflected radiance by clouds, atmospheric molecules, sun glint and bright desert surfaces. It achieves its calibration results through a combination of the results of these methods. The consistency with SPOT-VGT, essential for a continuity mission, will be verified through inter-calibration over stable desert sites. The vicarious calibration methods implemented in the OSCAR facility have been throughout tested and validated on various satellite data and detailed error assessments have been performed. These analyses showed that the mission requirement specifications for the radiometric calibration are realistic achievable goals. The Cal/Val commissioning phase will start after the platform and instrument verification and validation phase and is scheduled to be a three-month activity, running in the summer months of 2013. At the Calcon 2013 conference, the Cal/Val activitity will be ongoing. This will allow to present preliminary results and give a firsthand and very up-to-date view on the status of the in-flight calibration and the end-to-end image-quality assessment

In-Orbit Radiometric Calibration and Stability Monitoring of the PROBA-V Instrument

Since its launch in May 2013, the in-orbit radiometric performance of PROBA-V has been continuously monitored. Due to the absence of on-board calibration devices, in-flight performance monitoring and calibration relies fully on vicarious calibration methods. In this paper, the multiple vicarious calibration techniques used to verify radiometric accuracy and to perform calibration parameter updates are discussed. Details are given of the radiometric calibration activities during both the commissioning and operational phase. The stability of the instrument in terms of overall radiometry and dark current is analyzed. Results of an independent comparison against MERIS and SPOT VEGETATION-2 are presented. Finally, an outlook is provided of the on-going activities aimed at improving both data consistency over time and within-scene uniformity

Vicarious Calibration of PROBA-V: One Year in Orbit

The Belgian-ESA PROBA-V(egetation) satellite was successfully launched on May 7, 2013, with the aim of ensuring data continuity for the SPOT-VEGETATION user community. Users are served with daily global land coverage data in four multispectral bands at both 1/3 km and 1 km resolution. Absolutely essential to this continuity is that accurate radiometric calibration is established during commissioning and maintained throughout the mission. Due to size, weight and power constraints, the satellite does not contain on-board calibration devices and thus the in-flight radiometric calibration relies solely on vicarious calibration methods. A set of distinct methods is being used, including calibration over deep convective clouds, Rayleigh, bright desert surfaces and snow. They complement each other, allow to cross-check results and together they ensure that all calibration requirements are reached. The consistency with other missions, such as ENVISAT-MERIS and SPOT-VGT is, amongst other, verified through cross-calibration over the Libya 4 desert site. In addition to this, a lunar calibration method has been implemented. Lunar observations are acquired monthly with the instrument using a constant phase angle. The images are compared to the ROLO lunar reflectance model of USGS. The ROLO model, derived from thousands of lunar observations, simulates a disc equivalent reflection. When applied to observations with constant well known phase angle, outstanding temporal stability can be achieved with this model. A full-fledged implementation of the model has been done within VITO’s OSCAR (Optical Sensor CAlibration with simulated Radiances) facility, automatically generating calibration results when lunar images are acquired. The method allows to obtain multi-temporal calibration of the instrument. The absolute and multi temporal results are compared against those of the desert calibration method, inter-band results are compared against results of the deep convective clouds method. During the presentation, a brief overview will be given on the complete set of calibration methods used. Next, the results of the lunar calibration and their comparison against the other methods will be discussed in more detail