Publications (56)44.32 Total impact
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Article: On-Orbit Degradation of Solar Instruments
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ABSTRACT: We present the lessons learned about the degradation observed in several space solar missions, based on contributions at the Workshop about On-Orbit Degradation of Solar and Space Weather Instruments that took place at the Solar Terrestrial Centre of Excellence (Royal Observatory of Belgium) in Brussels on 3 May 2012. The aim of this workshop was to open discussions related to the degradation observed in Sun-observing instruments exposed to the effects of the space environment. This article summarizes the various lessons learned and offers recommendations to reduce or correct expected degradation with the goal of increasing the useful lifespan of future and ongoing space missions.Solar Physics 04/2013; · 2.78 Impact Factor -
Article: The SWAP EUV Imaging Telescope Part I: Instrument Overview and Pre-Flight Testing
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ABSTRACT: The Sun Watcher with Active Pixels and Image Processing (SWAP) is an EUV solar telescope on board ESA's Project for Onboard Autonomy 2 (PROBA2) mission launched on 2 November 2009. SWAP has a spectral bandpass centered on 17.4 nm and provides images of the low solar corona over a 54x54 arcmin field-of-view with 3.2 arcsec pixels and an imaging cadence of about two minutes. SWAP is designed to monitor all space-weather-relevant events and features in the low solar corona. Given the limited resources of the PROBA2 microsatellite, the SWAP telescope is designed with various innovative technologies, including an off-axis optical design and a CMOS-APS detector. This article provides reference documentation for users of the SWAP image data.08/2012; -
Article: The Projects for Onboard Autonomy (PROBA2) Science Centre: Sun Watcher Using APS Detectors and Image Processing (SWAP) and Large-Yield Radiometer (LYRA) Science Operations and Data Products
solphys. 07/2012; -
Article: Validation of CME Detection Software (CACTus) by Means of Simulated Data, and Analysis of Projection Effects on CME Velocity Measurements
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ABSTRACT: In the context of space weather forecasting, an automated detection of coronal mass ejections (CMEs) becomes more and more important for efficiently handling a large data flow which is expected from recently-launched and future solar missions. In this paper we validate the detection software package “CACTus” by applying the program to synthetic data from our 3D time-dependent CME simulations instead of observational data. The main strength of this study is that we know in advance what should be detected. We describe the sensitivities and strengths of automated detection, more specific for the CACTus program, resulting in a better understanding of CME detection on one hand and the calibration of the CACTus software on the other hand, suggesting possible improvements of the package. In addition, the simulation is an ideal tool to investigate projection effects on CME velocity measurements. KeywordsCorona, models, observations–Coronal mass ejections, initiation and propagation–Instrumentation and data management–MagnetohydrodynamicsSolar Physics 04/2012; 270(1):253-272. · 2.78 Impact Factor -
Article: CMOS-APS Detectors for Solar Physics: Lessons Learned during the SWAP Preflight Calibration
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ABSTRACT: CMOS-APS imaging detectors open new opportunities for remote sensing in solar physics beyond what classical CCDs can provide, offering far less power consumption, simpler electronics, better radiation hardness, and the possibility of avoiding a mechanical shutter. The SWAP telescope onboard the PROBA2 technology demonstration satellite of the European Space Agency will be the first actual implementation of a CMOS-APS detector for solar physics in orbit. One of the goals of the SWAP project is precisely to acquire experience with the CMOS-APS technology in a real-live space science context. Such a precursor mission is essential in the preparation of missions such as Solar Orbiter where the extra CMOS-APS functionalities will be hard requirements. The current paper concentrates on specific CMOS-APS issues that were identified during the SWAP preflight calibration measurements. We will discuss the different readout possibilities that the CMOS-APS detector of SWAP provides and their associated pros and cons. In particular we describe the “image lag” effect, which results in a contamination of each image with a remnant of the previous image. We have characterised this effect for the specific SWAP implementation and we conclude with a strategy on how to successfully circumvent the problem and actually take benefit of it for solar monitoring.Solar Physics 04/2012; 249(1):147-163. · 2.78 Impact Factor -
Article: Time delays in quasi-periodic pulsations observed during the X2.2 solarflare on 2011 February 15
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ABSTRACT: We report observations of quasi-periodic pulsations (QPPs) during the X2.2 flare of 2011 February 15, observed simultaneously in several wavebands. We focus on fluctuations on time scale 1-30 s and find different time lags between different wavebands. During the impulsive phase, the Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI) channels in the range 25-100 keV lead all the other channels. They are followed by the Nobeyama RadioPolarimeters at 9 and 17 GHz and the Extreme Ultra-Violet (EUV) channels of the Euv SpectroPhotometer (ESP) onboard the Solar Dynamic Observatory (SDO). The Zirconium and Aluminum filter channels of the Large Yield Radiometer (LYRA) onboard the Project for On-Board Autonomy (PROBA2) satellite and the SXR channel of ESP follow. The largest lags occur in observations from the Geostationary Operational Environmental Satellite (GOES), where the channel at 1-8 {\AA} leads the 0.5-4 {\AA} channel by several seconds. The time lags between the first and last channels is up to 9 s. We identified at least two distinct time intervals during the flare impulsive phase, during which the QPPs were associated with two different sources in the Nobeyama RadioHeliograph at 17 GHz. The radio as well as the hard X-ray channels showed different lags during these two intervals. To our knowledge, this is the first time that time lags are reported between EUV and SXR fluctuations on these time scales. We discuss possible emission mechanisms and interpretations, including flare electron trapping.The Astrophysical Journal Letters 04/2012; 749(1):L16. · 5.53 Impact Factor -
Article: Study of a Prominence Eruption using PROBA2/SWAP and STEREO/EUVI Data
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ABSTRACT: Observations of the early rise and propagation phases of solar eruptive prominences can provide clues about the forces acting on them through the behavior of their acceleration with height. We have analyzed such an event, observed on 13 April 2010 by SWAP on PROBA2 and EUVI on STEREO. A feature at the top of the erupting prominence was identified and tracked in images from the three spacecraft. The triangulation technique was used to derive the true direction of propagation of this feature. The reconstructed points were fitted with two mathematical models: i) a power-law polynomial function and ii) a cubic smoothing spline, in order to derive the accelerations. The first model is characterized by five degrees of freedom while the second one is characterized by ten degrees of freedom. The results show that the acceleration increases smoothly and it is continuously increasing with height. We conclude that the prominence is not accelerated immediately by local reconnection but rather is swept away as part of a large-scale relaxation of the coronal magnetic field.03/2012; -
Article: Signatures of the slow solar wind streams from active regions in the inner corona
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ABSTRACT: Some of local sources of the slow solar wind can be associated with spectroscopically detected plasma outflows at edges of active regions accompanied with specific signatures in the inner corona. The EUV telescopes (e.g. SPIRIT/CORONAS-F, TESIS/CORONAS-Photon and SWAP/PROBA2) sometimes observed extended ray-like structures seen at the limb above active regions in 1MK iron emission lines and described as "coronal rays". To verify the relationship between coronal rays and plasma outflows, we analyze an isolated active region (AR) adjacent to small coronal hole (CH) observed by different EUV instruments in the end of July - beginning of August 2009. On August 1 EIS revealed in the AR two compact outflows with the Doppler velocities V =10-30 km/s accompanied with fan loops diverging from their regions. At the limb the ARCH interface region produced coronal rays observed by EUVI/STEREO-A on July 31 as well as by TESIS on August 7. The rays were co-aligned with open magnetic field lines expanded to the streamer stalks. Using the DEM analysis, it was found that the fan loops diverged from the outflow regions had the dominant temperature of ~1 MK, which is similar to that of the outgoing plasma streams. Parameters of the solar wind measured by STEREO-B, ACE, WIND, STEREO-A were conformed with identification of the ARCH as a source region at the Wang-Sheeley-Arge map of derived coronal holes for CR 2086. The results of the study support the suggestion that coronal rays can represent signatures of outflows from ARs propagating in the inner corona along open field lines into the heliosphere.03/2012; -
Article: LYRA Observations of Two Oscillation Modes in a Single Flare
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ABSTRACT: We analyze light curves from the LYRA irradiance experiment on board PROBA2 during the flare of 2010 February 8. We see both long- and short-period oscillations during the flare. The long-period oscillation is interpreted in terms of standing slow sausage modes; the short-period oscillation is thought to be a standing fast sausage mode. The simultaneous presence of two oscillation modes in the same flaring structure allows for new coronal seismological applications. The periods are used to find seismological estimates of the plasma-β and the density contrast of the flaring loop. Also the wave mode number is estimated from the observed periods.The Astrophysical Journal 10/2011; 740(2):90. · 6.02 Impact Factor -
Chapter: Visualization of Distributed Solar Data and Metadata with the Solar Weather Browser
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ABSTRACT: The Solar Weather Browser (SWB) is a standalone, open-source software tool designed to display solar images with context overlays. It was originally developed for the space-weather forecast activities of the Solar Influence Data analysis Center (SIDC) but it is more generally well suited to display the output of solar-feature recognition methods. The SWB is also useful in the context of distributed solar-image archives, where it could play the role of a quick-look viewer. The SWB allows the user to visually browse large solar data sets and investigate the solar activity for a given date. It has a client – server design that minimizes the bandwidth from the network to the user’s monitor. The server processes the data using the SolarSoft library and distributes them through aWeb server to which the SWB client connects. The client is readily available for Linux, Mac OS X, and Windows at http://sidc.be/SWB. We discuss the software technology embedded in the SWB as well as its use for solar physics and space weather.08/2009: pages 15-22; -
Article: On 3D Reconstruction of Coronal Mass Ejections using SECCHI-COR Data
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ABSTRACT: The data from SECCHI-COR1 and SECCHI-COR2 coronagraphs onboard STEREO mission which was launched in October 2006 provided us with the first-ever stereoscopic images of the Sun's corona. These observations were found to be extremely useful in reconstructing the 3D structure of coronal mass ejections (CMEs). We apply four methods for reconstructing the CMEs: 1) Local correlation tracking (to identify the same feature in COR Ahead and COR Behind images) plus tie-point reconstruction technique; 2) Center of mass of the structures along the line of sight (i.e. along each epipolar lines) plus tie-point reconstruction technique; 3) Polarization ratio technique (see for e.g. Moran and Davila 2004); 4) Forward modelling technique (see Thernisien et al. 2006). The four techniques are applied on three structured CMEs observed by COR1 and COR2 instruments on 15 May 2007, 31 August 2007 and 25 March 2008. A comparison of results obtained from the application of the four reconstruction algorithms is presented and discussed.03/2009; 11:1145. -
Article: Automated LASCO CME catalog for solar cycle 23: are CMEs scale invariant?
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ABSTRACT: In this paper we present the first automatically constructed LASCO CME catalog, a result of the application of the Computer Aided CME Tracking software (CACTus) on the LASCO archive during the interval September 1997 - January 2007. We have studied the CME characteristics and have compared them with similar results obtained by manual detection (CDAW CME catalog). On average CACTus detects less than 2 events per day during solar minimum up to 8 events during maximum, nearly half of them being narrow (< 20 degrees). Assuming a correction factor, we find that the CACTus CME rate is surprisingly consistent with CME rates found during the past 30 years. The CACTus statistics show that small scale outflow is ubiquitously observed in the outer corona. The majority of CACTus-only events are narrow transients related to previous CME activity or to intensity variations in the slow solar wind, reflecting its turbulent nature. A significant fraction (about 15%) of CACTus-{\it only} events were identified as independent events, thus not related to other CME activity. The CACTus CME width distribution is essentially scale invariant in angular span over a range of scales from 20 to 120 degrees while previous catalogues present a broad maximum around 30 degrees. The possibility that the size of coronal mass outflows follow a power law distribution could indicate that no typical CME size exists, i.e. that the narrow transients are not different from the larger well-defined CMEs.10/2008; -
Article: LYRA: The solar UV radiometer aboard the ESA Proba-2
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ABSTRACT: LYRA is the solar UV radiometer that will embark in 2006 onboard Proba2, a technologically oriented ESA micro-mission. LYRA is designed and manufactured by a Belgian–Swiss–German consortium (ROB, PMOD/WRC, IMOMEC, CSL, MPS and BISA) with additional international collaborations. It will monitor the solar irradiance in four UV passbands. They have been chosen for their relevance to Solar Physics, Aeronomy and Space Weather: (1) the 115–125 nm Lyman-α channel, (2) the 200–220 nm Herzberg continuum range, (3) the Aluminium filter channel (17–70 nm) including He II at 30.4 nm and (4) the Zirconium filter channel (1–20 nm). The radiometric calibration will be traceable to synchrotron source standards (PTB and NIST). The stability will be monitored by onboard calibration sources (LEDs), which allow to distinguish between potential degradations of the detectors and filters. Additionally, a redundancy strategy maximizes the accuracy and the stability of the measurements. LYRA will benefit from wide bandgap detectors based on diamond: it will be the first space assessment of a pioneering UV detectors program. Diamond sensors make the instruments radiation-hard and solar-blind: their high bandgap energy makes them insensitive to visible light and, therefore, make dispensable visible light blocking filters, which seriously attenuate the desired ultraviolet signal. Their elimination augments the effective area and hence the signal-to-noise, therefore increasing the precision and the cadence. The SWAP EUV imaging telescope will operate next to LYRA on Proba2. Together, they will establish a high performance solar monitor for operational space weather nowcasting and research. LYRA demonstrates technologies important for future missions such as the ESA Solar OrbiterAdvances in Space Research 03/2006; 37(2):303-312. · 1.18 Impact Factor -
Article: LYRA, a solar UV radiometer on Proba2
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ABSTRACT: LYRA is the solar UV radiometer that will embark in 2006 onboard Proba2, a technologically oriented ESA micro-mission. LYRA is designed and manufactured by a Belgian–Swiss–German consortium (ROB, PMOD/WRC, IMOMEC, CSL, MPS and BISA) with additional international collaborations. It will monitor the solar irradiance in four UV passbands. They have been chosen for their relevance to Solar Physics, Aeronomy and Space Weather: (1) the 115–125 nm Lyman-α channel, (2) the 200–220 nm Herzberg continuum range, (3) the Aluminium filter channel (17–70 nm) including He II at 30.4 nm and (4) the Zirconium filter channel (1–20 nm). The radiometric calibration will be traceable to synchrotron source standards (PTB and NIST). The stability will be monitored by onboard calibration sources (LEDs), which allow to distinguish between potential degradations of the detectors and filters. Additionally, a redundancy strategy maximizes the accuracy and the stability of the measurements. LYRA will benefit from wide bandgap detectors based on diamond: it will be the first space assessment of a pioneering UV detectors program. Diamond sensors make the instruments radiation-hard and solar-blind: their high bandgap energy makes them insensitive to visible light and, therefore, make dispensable visible light blocking filters, which seriously attenuate the desired ultraviolet signal. Their elimination augments the effective area and hence the signal-to-noise, therefore increasing the precision and the cadence. The SWAP EUV imaging telescope will operate next to LYRA on Proba2. Together, they will establish a high performance solar monitor for operational space weather nowcasting and research. LYRA demonstrates technologies important for future missions such as the ESA Solar Orbiter.Advances in Space Research 01/2006; 37(2):303-312. · 1.18 Impact Factor -
Article: Swap: AN EUV Imager for Solar Monitoring on Board of PROBA2
10/2005; 596:70. -
Article: Interaction of EIT Wave With Active Regions on the Sun
08/2005; 592:535. -
Article: Space Weather with ESA's PROBA2 Mission
08/2005; 592:685. -
Article: Energetic Dymanics of EIT Wave Structure Analyzed by EIT Wave Detector
08/2005; 592:751. -
Conference Proceeding: SWAP and LYRA: space weather from a small spacecraft
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ABSTRACT: Two scientific instruments for Sun observations are being developed to be part of the payload of the ESA's second microsatellite, Proba-II (Project for On-board Autonomy). PROBA-2 is scheduled for launch in early 2007, on a low Earth orbit. Like Proba-1, in orbit since October 2001, Proba-2 is a 100-kilogram class spacecraft. PROBA-II will demonstrate new advanced technologies on its scientific payload but also on new platform subsystems such as star tracker, digital Sun sensor, cool gas generator, solar array concentrator, Li-Ion Battery, new central processor. This paper is dedicated to the solar payload, comprising the Sun Watcher using Active Pixel System detector and image Processing (SWAP) and the Lyman alpha Radiometer (LYRA), both aiming at Sun observations. SWAP, the Belgian-led main instrument, will continuously provide detailed images of the solar atmosphere, by the light of extreme ultraviolet rays, at 17.4 nm, completely absorbed by the terrestrial atmosphere. SWAP will perform as an operational solar monitoring tool for space weather forecasting while it will also demonstrate new technological solutions: CMOS/APS detector, new off-axis telescope design, a thermal structure. LYRA (LYman-alpha RAdiometer) is a small compact solar VUV radiometer. This instrument is designed, manufactured and calibrated by a Belgian-Swiss-German consortium. It will monitor the solar flux in four UV passbands. The spectral channels have been carefully selected for their relevance to space weather, solar physics and aeronomy, ranging from 1 nm to 220 nm. On the technological side, LYRA will benefit from the pioneering UV detectors program using diamond technology. The LYRA data will produce valuable solar monitoring information, for operational space weather nowcasting and research. This paper will detail the instrument concepts and their preparation for delivery to the platform.Recent Advances in Space Technologies, 2005. RAST 2005. Proceedings of 2nd International Conference on; 07/2005 -
Article: Entering The Era Of Automated Cme Recognition: A Review Of Existing Tools
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ABSTRACT: We consider the problem of the observational identification of CMEs. The ever growing importance of space weather has led to new requirements on the timeliness and objectiveness of CME detection. It is not sufficient any more to simply detect CMEs, a complete set of characteristics (speed, direction, mass, chirality) must be reported as soon as possible to estimate its geoeffectiveness. Recent developments in (solar) feature recognition greatly improved the ability to address these new needs. Progress was achieved in automating the detection of CMEs in coronagraphic data. This has led to near-real-time messages alerting the space weather community day and night. In attempting to generate ever-prompter alerts, we can employ a far broader set of solar observations than coronagraphic data alone. At present an extensive set of automatic recognition tools exists for a number of CME-related phenomena occurring in the lower corona. This paper deals with detection techniques for disappearing filaments in Hα images, dimmings, EIT waves and erupting prominences in radio data. We believe that incorporating all automatically generated alerts into one report per CME can provide valuable CME information, especially when no coronagraphic images are available. This paper is thus a quest to reach a maximal success rate with the help of an integrated system of tools acting on a variety of data. Future grid-technology systems will greatly facilitate this.Solar Physics 04/2005; 228(1):239-251. · 2.78 Impact Factor
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Institutions
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1999–2012
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Royal Observatory of Belgium
Brussels, BRU, Belgium -
Montana State University
Bozeman, MT, USA
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