scholarly journals Characterizing Spectral Channels of Visible Emission Line Coronagraph of Aditya-L1

2021 ◽  
Vol 8 ◽  
Author(s):  
Ritesh Patel ◽  
A. Megha ◽  
Arpit Kumar Shrivastav ◽  
Vaibhav Pant ◽  
M. Vishnu ◽  
...  
Keyword(s):  
Emission Line ◽  
Signal To Noise Ratio ◽  
Scattered Light ◽  
Plasma Temperature ◽  
Slit Width ◽  
Field Of View ◽  
Visible Emission ◽  
Line Profiles ◽  
Signal To Noise ◽  
Spectral Channels

Aditya-L1 is India’s first solar mission with the Visible Emission Line Coronagraph (VELC), which consists of three spectral channels taking high-resolution spectroscopic observations of the inner corona up to 1.5 Rʘ at 5,303, 7,892, and 10,747 Å. In this work, we present a strategy for the slit width optimization of the VELC using synthetic line profiles by taking into account the instrument characteristics and coronal conditions for log(T) varying from 6 to 6.5. The synthetic profiles are convolved with simulated instrumental scattered light and noise to estimate the signal-to-noise ratio (SNR), which will be crucial to designing the future observation plans. We find that the optimum slit width for VELC turns out to be 50 μm, providing sufficient SNR for observations in different solar conditions. We also analyzed the effect of plasma temperature on the SNR at different heights in the VELC field of view for the optimized slit width. We also studied the expected effect of the presence of a CME on the spectral channel observations. This analysis will help to plan the scientific observations of VELC in different solar conditions.

scholarly journals Automated detection of Coronal Mass Ejections in Visible Emission Line Coronagraph (VELC) on-board ADITYA-L1

2018 ◽  
Vol 13 (S340) ◽  
pp. 171-172
Author(s):  
Ritesh Patel ◽  
K. Amareswari ◽  
Vaibhav Pant ◽  
Dipankar Banerjee ◽  
K. Sankarasubramanian
Keyword(s):  
Emission Line ◽  
Coronal Mass Ejections ◽  
Detection Algorithm ◽  
Automated Detection ◽  
Field Of View ◽  
Visible Emission ◽  
Signal To Noise ◽  
Difference Images

AbstractAn onboard automated coronal mass ejections (CMEs) detection algorithm has been developed for Visible Emission Line Coronagraph (VELC) onboard ADITYA-L1. The aim of this algorithm is to reduce the load on telemetry by sending the high spatial (~ 2.51 arcsec pixel−1) and temporal (1 s) resolution images of corona from 1.05 R⊙ to 3 R⊙, containing CMEs and rejecting others. It is based on intensity thresholding followed by an area thresholding in successive running difference images which are re-binned to lower resolution to improve signal to noise. Here we present the results of application of the algorithm on synthetic corona images generated for the VELC field of view (FOV).

scholarly journals Photometric Characteristics of Data from the Hubble Space Telescope Goddard-High Resolution Spectrograph

1988 ◽  
Vol 132 ◽  
pp. 35-38
Author(s):  
Dennis C. Ebbets ◽  
Sara R. Heap ◽  
Don J. Lindler
Keyword(s):  
Exposure Time ◽  
Hubble Space Telescope ◽  
Signal To Noise Ratio ◽  
Scattered Light ◽  
Signal To Noise ◽  
Space Telescope ◽  
Additional Noise ◽  
Reduction Strategies ◽  
Noise Ratio

The G-HRS is one of four axial scientific instruments which will fly aboard the Hubble Space Telescope (ref 1,2). It will produce spectroscopic observations in the 1050 A ≤ λ ≤ 3300 A region with greater spectral, spatial and temporal resolution than has been possible with previous space-based instruments. Five first order diffraction gratings and one Echelle provide three modes of spectroscopic operation with resolving powers of R = λ/ΔΔ = 2000, 20000 and 90000. Two magnetically focused, pulse-counting digicon detectors, which differ only in the nature of their photocathodes, produce data whose photometric quality is usually determined by statistical noise in the signal (ref 3). Under ideal circumstances the signal to noise ratio increases as the square root of the exposure time. For some observations detector dark count, instrumental scattered light or granularity in the pixel to pixel sensitivity will cause additional noise. The signal to noise ratio of the net spectrum will then depend on several parameters, and will increase more slowly with exposure time. We have analyzed data from the ground based calibration programs, and have developed a theoretical model of the HRS performance (ref 4). Our results allow observing and data reduction strategies to be optimized when factors other than photon statistics influence the photometric quality of the data.

scholarly journals The Effect of Noise and Finite Sampling on the Line Profile Variations of m = 0 Modes

2000 ◽  
Vol 176 ◽  
pp. 383-383
Author(s):  
M. H. Montgomery
Keyword(s):  
Phase Shift ◽  
Signal To Noise Ratio ◽  
Mode Frequency ◽  
Line Profiles ◽  
Signal To Noise ◽  
A Value ◽  
Scuti Star ◽  
Finite Sampling ◽  
Sampling Times ◽  
Synthetic Line

Figure 1 is of the same form as Fig. 3 in Schrijvers et al. (1997): the upper part of each panel is the amplitude of the variation across the line at the mode frequency and the lower part is the phase shift of these two components across the line (in units of Φ). The parameters {Vavg, k, Ω/ω0, W} were chosen to have values representative of the δ Scuti star 4 CVn. Each panel in this array of plots has m=0, with a value of ∓ of 0, 1, or 2, and an inclination angle θi between 10° and 80°. In order to generate the synthetic line profiles, we use sampling times taken from the last week of the 1996 δ Scuti campaign on 4 CVn, and we assume that the signal-to-noise ratio of the spectrum is 250.

scholarly journals Analysis of Signal to Noise Ratio in Coronagraph Observations of Coronal Mass Ejections

2020 ◽  
Author(s):  
Johannes Hinrichs ◽  
Jackie A. Davies ◽  
Matthew J. West ◽  
Volker Bothmer ◽  
Bram Bourgoignie ◽  
...  
Keyword(s):  
Coronal Mass Ejections ◽  
Signal To Noise Ratio ◽  
European Space Agency ◽  
Leading Edge ◽  
Outer Edge ◽  
Field Of View ◽  
Signal To Noise ◽  
Space Agency ◽  
Noise Ratio ◽  
Improved Performance

<p>Aims. We analyse the Signal-to-Noise Ratio (SNR) requirements of the European Space Agency (ESA)-funded Solar Coronagraph for OPErations (SCOPE) instrument with respect to the manual and automatic detection of Coronal Mass Ejections (CMEs) in its field of view of 2.5 to 30 solar radii.<br />Methods. For our analysis, SNR values are estimated from observations made by the C3 coronagraph on the Solar and Heliospheric Observatory (SOHO) spacecraft for a number of di erent CMEs. Additionally, we generate a series of artificial coronagraph images, each consisting of a modelled coronal background and a CME, the latter simulated using the Graduated Cylindrical Shell (GCS) model together with the SCRaytrace code available in the Interactive Data Language (IDL) SolarSoft library. Images are created with CME SNR levels between 0.5 and 10 at the outer<br />field of view (FOV) edge, generated by adding Poisson noise, and velocities between 700 km s-1 and 2800 kms-1. The images are analysed for the detectability of the CME above the noise with the automatic CME detection tool CACTus.<br />Results. We find in the analysed C3 images that CMEs near the outer edge of the field of view are typically 2%of the total brightness and have an SNR between 1 and 4 at their leading edge. The automated detection of CMEs in our simulated images by CACTus succeeded well down to SNR = 1 and for CME velocities up to 1400 kms-1. At lower SNR and higher velocity of 2100 kms-1 the detection started to break down. For SCOPE, the results from the two approaches confirm that the initial design goal of SNR = 4 would, if achieved, deliver improved performance over established data used in operations today.</p>

scholarly journals Impact of Micro-, Mini- and Multi-Electrode Mapping on Ventricular Substrate Characterisation

2020 ◽  
Vol 9 (3) ◽  
pp. 128-135
Author(s):  
Benjamin Berte ◽  
Katja Zeppenfeld ◽  
Roderick Tung
Keyword(s):  
Ventricular Tachycardia ◽  
Cardiac Arrhythmias ◽  
Signal To Noise Ratio ◽  
Near Field ◽  
Field Of View ◽  
Ablation Catheter ◽  
Signal To Noise ◽  
Voltage Mapping ◽  
Practice Variations ◽  
Catheter Technology

Accurate substrate characterisation may improve the evolving understanding and treatment of cardiac arrhythmias. During substrate-based ablation techniques, wide practice variations exist with mapping via dedicated multi-electrode catheter or conventional ablation catheters. Recently, newer ablation catheter technology with embedded mapping electrodes have been introduced. This article focuses on the general misconceptions of voltage mapping and more specific differences in unipolar and bipolar signal morphology, field of view, signal-to-noise ratio, mapping capabilities (density and resolution), catheter-specific voltage thresholds and impact of micro-, mini- and multi-electrodes for substrate mapping. Efficiency and cost-effectiveness of different catheter types are discussed. Increasing sampling density with smaller electrodes allows for higher resolution with a greater likelihood to record near-field electrical information. These advances may help to further improve our mechanistic understanding of the correlation between substrate and ventricular tachycardia, as well as macro-reentry arrhythmia in humans.

The effect of activity outside the field-of-view on image signal-to-noise ratio for 3D PET with15O

2011 ◽  
Vol 56 (10) ◽  
pp. 3061-3072 ◽  
Author(s):  
Masanobu Ibaraki ◽  
Shigeki Sugawara ◽  
Kazuhiro Nakamura ◽  
Fumiko Kinoshita ◽  
Toshibumi Kinoshita
Keyword(s):  
Signal To Noise Ratio ◽  
Field Of View ◽  
Signal To Noise ◽  
Noise Ratio ◽  
3D Pet

scholarly journals Computed Spectral Line Variations for Oblique Nonradial Pulsators

1986 ◽  
Vol 90 ◽  
pp. 234-234
Author(s):  
Dietrich Baade ◽  
Werner W. Weiss
Keyword(s):  
Spectral Line ◽  
Observational Data ◽  
Rotation Axis ◽  
Signal To Noise Ratio ◽  
Line Of Sight ◽  
Pulsation Velocity ◽  
Line Profiles ◽  
Signal To Noise ◽  
Velocity Amplitude ◽  
Mode Order

AbstractSpectral line profiles are computed for nonradially pulsating CP2 stars. For a range which currently is thought to be typical for these stars, the influence of six parameters on the line profiles is considered: mode order ℓ and degree m, pulsation velocity amplitude, the angle between the rotation and pulsation axis, the angle between the rotation axis and the line-of-sight, and the phase angle of the rotation. In view of the expected low signal-to-noise ratio of observational data it is investigated to what extent easily measurable, simple quantities can still be useful in discriminating between different modes.

scholarly journals A phantom study to contrast and compare polymer and gold fiducial markers in radiotherapy simulation imaging

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Daryl Lim Joon ◽  
Drew Smith ◽  
Mark Tacey ◽  
Michal Schneider ◽  
Benjamin Harris ◽  
...  
Keyword(s):  
Signal To Noise Ratio ◽  
Fiducial Markers ◽  
Line Profiles ◽  
Signal To Noise ◽  
Gray Scale ◽  
Tissue Equivalent ◽  
Tissue Equivalent Phantom ◽  
Noise Ratio ◽  
Prostate Cancer Radiotherapy ◽  
Ct And Mri

AbstractTo assess visibility and artifact characteristics of polymer fiducials compared to standard gold fiducials for radiotherapy CT and MRI simulation. Three gold and three polymer fiducials were inserted into a CT and MRI tissue-equivalent phantom that approximated the prostate cancer radiotherapy configuration. The phantom and fiducials were imaged on CT and MRI. Images were assessed in terms of fiducial visibility and artifact. ImageJ was employed to quantify the pixel gray-scale of each fiducial and artifact. Fiducial gray-scale histograms and profiles were generated for analysis. Objective measurements of the contrast-to-noise ratio (CNR), signal-to-noise ratio (SNR), and artifact index (AI) were calculated. The CT images showed that the gold fiducials are visually brighter, with greater contrast than the polymer. The higher peak values illustrate this in the line profiles. However, they produce bright radiating and dark shadowing artifacts. This is depicted by the greater width of line profiles and the disruption of phantom area profiles. Quantitatively this results in greater percentile ranges of the histograms. Furthermore, for CT, gold had a higher CNR than polymer, relative to the phantom. However, the gold CNR and SNR were degraded by the greater artifact and thus AI. Both fiducials were visible on MRI and had similar histograms and profiles that were also reflected in comparable CNR, SNR and AI. Polymer fiducials were well visualized in a phantom on CT and MR and produce less artifact than the gold fiducials. Polymer markers could enhance the quality and accuracy of radiotherapy co-registration and planning but require clinical confirmation.

scholarly journals Versatile Multi-Detector Scheme for Adaptive Optics Scanning Laser Ophthalmoscopy

2018 ◽  
Author(s):  
Sanam Mozaffari ◽  
Volker Jaedicke ◽  
Francesco Larocca ◽  
Pavan Tiruveedhula ◽  
Austin Roorda
Keyword(s):  
Adaptive Optics ◽  
Signal To Noise Ratio ◽  
Scattered Light ◽  
Scanning Laser ◽  
Retinal Vasculature ◽  
Single Element ◽  
Scanning Laser Ophthalmoscopy ◽  
Signal To Noise ◽  
Detection Scheme ◽  
Multiple Detectors

AbstractAdaptive Optics Scanning Laser Ophthalmoscopy (AOSLO) is a powerful tool for imaging the retina at high spatial and temporal resolution. In this paper, we present a multi-detector scheme for AOSLO which has two main configurations: pixel reassignment and offset aperture imaging. In this detection scheme, the single element detector of the standard AOSLO is replaced by a fiber bundle which couples the detected light into multiple detectors. The pixel reassignment configuration allows for more light throughput while maintaining optimal confocal resolution. The increase in signal-to-noise ratio (SNR) from this configuration can improve the accuracy of motion registration techniques. The offset aperture imaging configuration enhances the detection of multiply scattered light, which improves the contrast of retinal vasculature and inner retinal layers similar to methods such as nonconfocal split-detector imaging and multi-offset aperture imaging.

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