Figure testing and calibration of the ISOON Fabry-Perot etalons
06 Oct 2011-Proceedings of SPIE (International Society for Optics and Photonics)-Vol. 8148, pp 125-137
TL;DR: In this paper, the authors present the methods and results for the figure testing and spectral calibration of the narrow and wide-band etalons for the Improved Solar Observing Optical Network's dual-etalon tunable imaging filters.
Abstract: We present the methods and results for the figure testing and spectral calibration of the narrow- and wide-band etalons
for the Improved Solar Observing Optical Network's dual-etalon tunable imaging filters. The ISOON system comprises a
distributed network of ground-based patrol telescopes that gather full-disk data for the monitoring of solar activity and
for the development of more reliable space weather models. The etalon figure testing consists mainly of testing the
cavity flatness and coating uniformity of each etalon. For this testing a series of exposures is taken as the etalon is tuned
through a stable spectral line and a full-aperture line profile correlation method is employed to map the variations in the
effective cavity thickness. Calibration of the etalons includes absolute calibration of the cavity mean spacing change
corresponding to a controller step and calibration of plate parallelism and spacing settings for each spectral region of
interest. Developmental acceptance testing and calibration procedures were performed in a laboratory environment using
a HeNe laser source. A calibration method that uses illumination in the telluric lines is also described. This latter method
could be used to conduct calibration in the field without the use of an artificial light source.
Citations
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18 Nov 2014
TL;DR: In this article, the tilt information of the scanning mirror is extracted from the multi-beam fringe pattern and the Radon transform is used to extract the tilted plane of the moving mirror.
Abstract: Tunable Fabry–Perot (F-P) based narrow band filter has been widely used in large solar telescope, which is utilized to
isolate an arbitrary wavelength that we are interested in by adjusting the cavity length. However, it is difficult to
guarantee that the mirror scan strictly parallel. As a result, the observations of the solar telescope would be affected. Here,
we proposed a method to extract the tilt information of the scanning mirror. At first, the interferogram is obtained on the
outer surface of the F-P interferometer. Then an interferogram of double-path is obtained from the multi-beam fringe
pattern, which contains the tilt information of the moving mirror. Finally, the Radon transform is used in processing the
interferogram to extract the tilted plane. Good results come out of the simulation of this method. It has high accuracy and
high stability. It can provide feedback information to the closed-loop control system, and guide the tilt correction.
3 citations
References
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Book•
01 Jan 1986
TL;DR: In this article, the authors describe the Fabry-Perot interferometer and its variants as well as its use, optimisation and applications, and discuss its classical uses in metrology and its contemporary applications.
Abstract: This book describes the Fabry-Perot interferometer and its variants as well as its use, optimisation and applications. The author begins with an historical perspective on the development of the instrument. Because of the quantitative uses of the device, the text tends to be mostly mathematical in its treatment. However, there is also much practical detail on the use and optimization of the Fabry-Perot interferometer and discussion of its classical uses (such as in metrology) and its contemporary applications (such as in lasers). In addition the book contains a comprehensive bibliography summarizing the extensive literature on the subject. This book will appeal both to high-resolution practitioners, such as spectroscopists, and to the laser community, since the Fabrv-Perot is not only an integral part of the laser but is also usea to characterize its optical and spectroscopic behaviour.
307 citations
TL;DR: In this article, an analysis of multiwavelength data sets for a solar eruption at ~21:30 UT on 2002 December 19 showed evidence for the disappearance of a large-scale, transequatorial coronal loop (TL).
Abstract: Analyses of multiwavelength data sets for a solar eruption at ~21:30 UT on 2002 December 19 show evidence for the disappearance of a large-scale, transequatorial coronal loop (TL). In addition, coronal manifestations of the eruption (based on SOHO EIT and LASCO images) include large-scale coronal dimming, flares in each associated active region in the northern and southern hemispheres, and a halo CME. We present detailed observations of the chromospheric aspects of this event based on Hα images obtained with the ISOON telescope. The ISOON images reveal distant flare precursor brightenings, sympathetic flares, and, of most interest herein, four nearly cospatial propagating chromospheric brightenings. The speeds of the propagating disturbances causing these brightenings are 600-800 km s-1. The inferred propagating disturbances have some of the characteristics of Hα and EIT flare waves (e.g., speed, apparent emanation from the flare site, subsequent filament activation). However, they differ from typical Hα chromospheric flare waves (also known as Moreton waves) because of their absence in off-band Hα images, small angular arc of propagation (<30°), and their multiplicity. Three of the four propagating disturbances consist of a series of sequential chromospheric brightenings of network points that suddenly brighten in the area beneath the TL that disappeared earlier. SOHO MDI magnetograms show that the successively brightened points that define the inferred propagating disturbances were exclusively of one polarity, corresponding to the dominant polarity of the affected region. We speculate that the sequential chromospheric brightenings represent footpoints of field lines that extend into the corona, where they are energized in sequence by magnetic reconnection as coronal fields tear away from the chromosphere during the eruption of the transequatorial CME. We report briefly on three other events with similar narrow propagating disturbances that were confined to a single hemisphere.
54 citations
TL;DR: In this article, a detailed investigation of the thermal and velocity structure in an isolated sunspot, using the Fe I 5576 A spectral line, is presented, and the concept of flowless maps is incorporated, to separate velocity and intensity effects.
Abstract: The purpose of this paper is (1) to confirm and establish the working of a dual-etalon Fabry-Perot imaging spectroscopy system at the National Solar Observatory/Sacramento Peak Dunn Solar Telescope and (2) to use this system to extend previous work by many authors and understand the structure and dynamics of sunspots. A detailed investigation of the thermal and velocity structure in an isolated sunspot, using the Fe I 5576 A spectral line, is presented. The concept of flowless maps is incorporated, to separate velocity and intensity effects. The resulting intensities are used to generate thermal maps of the sunspot along the height of formation of a spectral line, followed by a thermal span map. The thermal span in penumbral regions is in the range of 1350-1580 K. It is a factor of 2 smaller in the umbra. Using spectral line bisectors, we extend the concept of a velocity span to a sunspot, following Gray. The velocity span is used to study the velocity gradients across a sunspot. The velocity span maximizes in the middle of the sunspot penumbra and falls off on either side. The Doppler-neutralized mean bisectors from the disk-side and limb-side penumbra show more sharply inclined gradients, when compared with the C-shaped photospheric bisectors. The mean umbral bisectors show sharp, <-shaped profiles. In most of the penumbra, the individual bisectors are sharply inclined, with a shape of "/" or "\," indicative of a highly suppressed convective flow. The intensity and velocity data show that a new family of penumbral filaments rises in the middle penumbra. Bisector intensity-velocity relationships display opposite gradients in the inner and outer penumbra, showing the rising and falling parts of curved penumbral flux tubes. Some clustering of the bisector intensity-velocity relationship is perhaps due to the fluted nature of flux tubes.
20 citations
TL;DR: In this paper, a fast flat field algorithm was presented that uses two orthogonal constant speed scans of an image across a detector to compute a flat field, each scan image calibrates the cross-scan direction of the other.
Abstract: A fast flat‐fielding algorithm is presented that uses two orthogonal constant‐speed scans of an image across a detector to compute a flat field. Each scan image calibrates the cross‐scan direction of the other. Results from the ISOON solar telescope are presented. For a camera with \documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \usepackage{portland,xspace} \usepackage{amsmath,amsxtra} \usepackage[OT2,OT1]{fontenc}
ewcommand\cyr{ \renewcommand\rmdefault{wncyr} \renewcommand\sfdefault{wncyss} \renewcommand\encodingdefault{OT2}
ormalfont \selectfont} \DeclareTextFontCommand{\textcyr}{\cyr} \pagestyle{empty} \DeclareMathSizes{10}{9}{7}{6} \begin{document} \landscape $2048\times 2048$ \end{document} pixels, the computation requires 30 s of processing time and yields a result that is comparable to a Kuhn‐Lin flat field, which requires 1 hr of processing time o...
11 citations
Journal Article•
TL;DR: In this paper, a haute precision de profils et bissectrices de 4 raies rotationnelles de O 2 terrestre is presented, and a Calcul theorique des profils de raie et des bissectures a l'aide d'un modele standard de l'atmosphere terrestres.
Abstract: On presente des mesures a haute precision de profils et bissectrices de 4 raies rotationnelles de O 2 terrestre a 6280 A Calcul theorique des profils de raie et des bissectrices a l'aide d'un modele standard de l'atmosphere terrestre
9 citations