References of "Solar Physics"
     in
Bookmark and Share    
Full Text
Peer Reviewed
See detailThe SWAP EUV Imaging Telescope. Part II: In-flight Performance and Calibration
Halain, Jean-Philippe ULg; Berghmans, David; Seaton, Dan et al

in Solar Physics (2013), 286

The Sun Watcher with Active Pixel System detector and Image Processing (SWAP) telescope was launched on 2 November 2009 onboard the ESA PROBA2 technological mission and has acquired images of the solar ... [more ▼]

The Sun Watcher with Active Pixel System detector and Image Processing (SWAP) telescope was launched on 2 November 2009 onboard the ESA PROBA2 technological mission and has acquired images of the solar corona every one to two minutes for more than two years. The most important technological developments included in SWAP are a radiation-resistant CMOS-APS detector and a novel onboard data-prioritization scheme. Although such detectors have been used previously in space, they have never been used for long-term scientific observations on orbit. Thus SWAP requires a careful calibration to guarantee the science return of the instrument. Since launch we have regularly monitored the evolution of SWAP’s detector response in-flight to characterize both its performance and degradation over the course of the mission. These measurements are also used to reduce detector noise in calibrated images (by subtracting dark-current). Because accurate measurements of detector dark-current require large telescope off-points, we also monitored straylight levels in the instrument to ensure that these calibration measurements are not contaminated by residual signal from the Sun. Here we present the results of these tests and examine the variation of instrumental response and noise as a function of both time and temperature throughout the mission. [less ▲]

Detailed reference viewed: 34 (10 ULg)
Full Text
Peer Reviewed
See detailThe SWAP EUV Imaging Telescope Part I: Instrument Overview and Pre-Flight Testing
Seaton, Daniel; Berghmans, David; Nicula, Bogdan et al

in Solar Physics (2013), 286

The Sun Watcher with Active Pixels and Image Processing (SWAP) is an EUV solar telescope onboard ESA’s Project for Onboard Autonomy 2 (PROBA2) mission launched on 2 November 2009. SWAP has a spectral ... [more ▼]

The Sun Watcher with Active Pixels and Image Processing (SWAP) is an EUV solar telescope onboard 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 54 × 54 arcmin field-of-view with 3.2 arcsec pixels and an imaging cadence of about two minutes. SWAP is designed to monitor all space-weatherrelevant 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. [less ▲]

Detailed reference viewed: 19 (7 ULg)
Full Text
Peer Reviewed
See detailStraylight-Rejection Performance of the STEREO HI Instruments
Halain, Jean-Philippe ULg; Rochus, Pierre ULg; Defise, Jean-Marc ULg et al

in Solar Physics (2011)

The SECCHI Heliospheric Imager (HI) instruments on-board the STEREO spacecraft have been collecting images of solar wind transients, including coronal mass ejections, as they propagate through the inner ... [more ▼]

The SECCHI Heliospheric Imager (HI) instruments on-board the STEREO spacecraft have been collecting images of solar wind transients, including coronal mass ejections, as they propagate through the inner heliosphere since the beginning of 2007. The scientific use of the images depends critically on the performance of the instruments and its evolution over time. One of the most important factors affecting the performance of the instrument is the rejection of straylight from the Sun and from other bright objects located both within and outside the HI fields of view. This paper presents an analysis of the evolution of the straylight-rejection performance of the HI instrument on each of the two STEREO spacecraft over the three first years of the mission. The straylight level has been evaluated and expressed in mean solar brightness units, in which such scientific observations are usually quoted, using photometric conversion factors. [less ▲]

Detailed reference viewed: 40 (14 ULg)
Full Text
Peer Reviewed
See detailThe Heliospheric Imagers Onboard the STEREO Mission
Eyles, C. J.; Harrison, R. A.; Davis, C. et al

in Solar Physics (2009), 254

Mounted on the sides of two widely separated spacecraft, the two Heliospheric Imager (HI) instruments onboard NASA's STEREO mission view, for the first time, the space between the Sun and Earth. These ... [more ▼]

Mounted on the sides of two widely separated spacecraft, the two Heliospheric Imager (HI) instruments onboard NASA's STEREO mission view, for the first time, the space between the Sun and Earth. These instruments are wide-angle visible-light imagers that incorporate sufficient baffling to eliminate scattered light to the extent that the passage of solar coronal mass ejections (CMEs) through the heliosphere can be detected. Each HI instrument comprises two cameras, HI-1 and HI-2, which have 20° and 70° fields of view and are off-pointed from the Sun direction by 14.0° and 53.7°, respectively, with their optical axes aligned in the ecliptic plane. This arrangement provides coverage over solar elongation angles from 4.0° to 88.7° at the viewpoints of the two spacecraft, thereby allowing the observation of Earth-directed CMEs along the Sun -- Earth line to the vicinity of the Earth and beyond. Given the two separated platforms, this also presents the first opportunity to view the structure and evolution of CMEs in three dimensions. The STEREO spacecraft were launched from Cape Canaveral Air Force Base in late October 2006, and the HI instruments have been performing scientific observations since early 2007. The design, development, manufacture, and calibration of these unique instruments are reviewed in this paper. Mission operations, including the initial commissioning phase and the science operations phase, are described. Data processing and analysis procedures are briefly discussed, and ground-test results and in-orbit observations are used to demonstrate that the performance of the instruments meets the original scientific requirements. [less ▲]

Detailed reference viewed: 154 (22 ULg)
Full Text
Peer Reviewed
See detailCMOS-APS Detectors for Solar Physics: Lessons Learned during the SWAP Preflight Calibration
De Groof, Anik; Berghmans, David; Nicula, Bogdan et al

in Solar Physics (2008)

Detailed reference viewed: 23 (3 ULg)
Full Text
Peer Reviewed
See detailFirst Imaging of Coronal Mass Ejections in the Heliosphere Viewed from Outside the Sun Earth Line
Harrison, Richard A; Davis, Christopher J; Eyles, Christopher J et al

in Solar Physics (2007), 247

We show for the first time images of solar coronal mass ejections (CMEs) viewed using the Heliospheric Imager (HI) instrument aboard the NASA STEREO spacecraft. The HI instruments are wide-angle imaging ... [more ▼]

We show for the first time images of solar coronal mass ejections (CMEs) viewed using the Heliospheric Imager (HI) instrument aboard the NASA STEREO spacecraft. The HI instruments are wide-angle imaging systems designed to detect CMEs in the heliosphere, in particular, for the first time, observing the propagation of such events along the Sun Earth line, that is, those directed towards Earth. At the time of writing the STEREO spacecraft are still close to the Earth and the full advantage of the HI dual-imaging has yet to be realised. However, even these early results show that despite severe technical challenges in their design and implementation, the HI instruments can successfully detect CMEs in the heliosphere, and this is an extremely important milestone for CME research. For the principal event being analysed here we demonstrate an ability to track a CME from the corona to over 40 degrees. The time altitude history shows a constant speed of ascent over at least the first 50 solar radii and some evidence for deceleration at distances of over 20 degrees. Comparisons of associated coronagraph data and the HI images show that the basic structure of the CME remains clearly intact as it propagates from the corona into the heliosphere. Extracting the CME signal requires a consideration of the F-coronal intensity distribution, which can be identified from the HI data. Thus we present the preliminary results on this measured F-coronal intensity and compare these to the modelled F-corona of Koutchmy and Lamy ( IAU Colloq. 85, 63, 1985). This analysis demonstrates that CME material some two orders of magnitude weaker than the F-corona can be detected; a specific example at 40 solar radii revealed CME intensities as low as 1.7×10[SUP]-14[/SUP] of the solar brightness. These observations herald a new era in CME research as we extend our capability for tracking, in particular, Earth-directed CMEs into the heliosphere. [less ▲]

Detailed reference viewed: 22 (2 ULg)
Full Text
Peer Reviewed
See detailObservations of Coronal Structures Above an Active Region by EIT and Implications for Coronal Energy Deposition
Neupert, W. M.; Newmark, J.; Delaboudinière, J.-P. et al

in Solar Physics (1998), 183

Solar EUV images recorded by the EUV Imaging Telescope (EIT) on SOHO have been used to evaluate temperature and density as a function of position in two largescale features in the corona observed in the ... [more ▼]

Solar EUV images recorded by the EUV Imaging Telescope (EIT) on SOHO have been used to evaluate temperature and density as a function of position in two largescale features in the corona observed in the temperature range of 1.0-2.0MK. Such observations permit estimates of longitudinal temperature gradients (if present) in the corona and, consequently, estimates of thermal conduction and radiative losses as a function of position in the features. We examine two relatively cool features as recorded in EIT's Feix/x (171Å) and Fexii (195Å) bands in a decaying active region. The first is a long-lived loop-like feature with one leg, ending in the active region, much more prominent than one or more distant footpoints assumed to be rooted in regions of weakly enhanced field. The other is a near-radial feature, observed at the West limb, which may be either the base of a very high loop or the base of a helmet streamer. We evaluate energy requirements to support a steady-state energy balance in these features and find in both instances that downward thermal conductive losses (at heights above the transition region) are inadequate to support local radiative losses, which are the predominant loss mechanism. The requirement that a coronal energy deposition rate proportional to the square of the ambient electron density (or pressure) is present in these cool coronal features provides an additional constraint on coronal heating mechanisms. [less ▲]

Detailed reference viewed: 34 (8 ULg)
Full Text
Peer Reviewed
See detailEIT and LASCO Observations of the Initiation of a Coronal Mass Ejection
Dere, K. P.; Brueckner, G. E.; Howard, R. A. et al

in Solar Physics (1997), 175

We present the first observations of the initiation of a coronal mass ejection (CME) seen on the disk of the Sun. Observations with the EIT experiment on SOHO show that the CME began in a small volume and ... [more ▼]

We present the first observations of the initiation of a coronal mass ejection (CME) seen on the disk of the Sun. Observations with the EIT experiment on SOHO show that the CME began in a small volume and was initially associated with slow motions of prominence material and a small brightening at one end of the prominence. Shortly afterward, the prominence was accelerated to about 100 km s[SUP]-1[/SUP] and was preceded by a bright loop-like structure, which surrounded an emission void, that traveled out into the corona at a velocity of 200 400 km s[SUP]-1[/SUP]. These three components, the prominence, the dark void, and the bright loops are typical of CMEs when seen at distance in the corona and here are shown to be present at the earliest stages of the CME. The event was later observed to traverse the LASCO coronagraphs fields of view from 1.1 to 30 Ro. Of particular interest is the fact that this large-scale event, spanning as much as 70 deg in latitude, originated in a volume with dimensions of roughly 35" (2.5 x 10[SUP]4[/SUP] km). Further, a disturbance that propagated across the disk and a chain of activity near the limb may also be associated with this event as well as a considerable degree of activity near the west limb. [less ▲]

Detailed reference viewed: 39 (11 ULg)
Full Text
Peer Reviewed
See detailEIT Observations of the Extreme Ultraviolet Sun
Moses, D.; Clette, Frédéric; Delaboudinière, J.-P. et al

in Solar Physics (1997), 175

The Extreme Ultraviolet Imaging Telescope (EIT) on board the SOHO spacecraft has been operational since 2 January 1996. EIT observes the Sun over a 45 x 45 arc min field of view in four emission line ... [more ▼]

The Extreme Ultraviolet Imaging Telescope (EIT) on board the SOHO spacecraft has been operational since 2 January 1996. EIT observes the Sun over a 45 x 45 arc min field of view in four emission line groups: Feix, x, Fexii, Fexv, and Heii. A post-launch determination of the instrument flatfield, the instrument scattering function, and the instrument aging were necessary for the reduction and analysis of the data. The observed structures and their evolution in each of the four EUV bandpasses are characteristic of the peak emission temperature of the line(s) chosen for that bandpass. Reports on the initial results of a variety of analysis projects demonstrate the range of investigations now underway: EIT provides new observations of the corona in the temperature range of 1 to 2 MK. Temperature studies of the large-scale coronal features extend previous coronagraph work with low-noise temperature maps. Temperatures of radial, extended, plume-like structures in both the polar coronal hole and in a low latitude decaying active region were found to be cooler than the surrounding material. Active region loops were investigated in detail and found to be isothermal for the low loops but hottest at the loop tops for the large loops. [less ▲]

Detailed reference viewed: 25 (6 ULg)
Full Text
Peer Reviewed
See detailEIT: Extreme-Ultraviolet Imaging Telescope for the SOHO Mission
Delaboudinière, J.-P.; Artzner, G. E.; Brunaud, J. et al

in Solar Physics (1995), 162

The Extreme-ultraviolet Imaging Telescope (EIT) will provide wide-field images of the corona and transition region on the solar disc and up to 1.5 Ro above the solar limb. Its normal incidence multilayer ... [more ▼]

The Extreme-ultraviolet Imaging Telescope (EIT) will provide wide-field images of the corona and transition region on the solar disc and up to 1.5 Ro above the solar limb. Its normal incidence multilayer-coated optics will select spectral emission lines from Fe IX (171 Å), Fe XII (195 Å), Fe XV (284 Å), and He II (304 Å) to provide sensitive temperature diagnostics in the range from 6 × 10[SUP]4[/SUP] K to 3 × 10[SUP]6[/SUP] K. The telescope has a 45 x 45 arcmin field of view and 2.6 arcsec pixels which will provide approximately 5-arcsec spatial resolution. The EIT will probe the coronal plasma on a global scale, as well as the underlying cooler and turbulent atmosphere, providing the basis for comparative analyses with observations from both the ground and other SOHO instruments. This paper presents details of the EIT instrumentation, its performance and operating modes. [less ▲]

Detailed reference viewed: 50 (6 ULg)