Restoration of Videos Degraded by Local Isoplanatism Effects in the Near-Infrared Domain

When observing a scene horizontally at a long distance in the near-infrared domain, degradations due to atmospheric turbulence often occur. In our previous work, we presented two hybrid methods to restore videos degraded by such local perturbations. These restoration algorithms take advantages of a space-time Wiener filter and a space-time regularization by the Laplacian operator. Wiener and Laplacian regularization results are mixed differently depending on the distance between the current pixel and the nearest edge point. It was shown that a gradation between Wiener and Laplacian areas improves results quality, so that only the algorithm using a gradation will be used in this article. In spite of a significant improvement in the obtained images quality, our restoration results greatly depend on the segmentation image used in the video processing. We then propose a method to select automatically the best segmentation image

Observations, analysis and interpretation with non-LTE of chromospheric structures of the Sun

This thesis is based on observations performed at the Vacuum Tower Telescope (Tenerife). We have used an infrared spectropolarimeter (TIP) and a Fabry-Perot spectrometer (G-FPI) from years 2004 to 2006. We have applied several imaging speckle reconstruction techniques, and compared them. We have studied chromospheric dynamics inside the solar disc and at the limb using H\alpha with very high spatial, spectral and temporal resolution. Keywords (see full abstract for details): fibrils, surge, MHD waves, speckle, blind deconvolution, Fabry-Perot, mini-flares, cloud model, spicules in Halpha, spicules continuing on the disc) Using He I 10830 we studied the offlimb spicular spectral I profiles with height over the limb. The analysis shows the variation of the off-limb emission profiles as a function of the distance to the visible solar limb. The intensity ratio of the multiplet (which is related to the optical thickness and coronal irradiation) is studied and compared with standard atmospheric models. We report observational properties from high-resolution filtergrams in the H$\alpha$ spectral line taken with the G-FPI. We find that spicules can reach heights of 8 Mm above the limb. We show that spicules outside the limb continue as dark fibrils inside the disc.Comment: PhD thesis. 107 pages. Source .tex files and images available at http://www.brunosan.e

Multi-Conjugate Adaptive Optics for LINC-NIRVANA : Laboratory Tests of a Ground-Layer Adaptive Optics System and Virtical Turbulence Measurements at Mt. Graham

Turbulence in Earth's atmosphere severely limits the image quality of ground-based telescopes. With the technique of Adaptive Optics, the induced distortions of the light can be measured and corrected in real-time, regaining nearly diffraction-limited performance. Unfortunately, when using a single guide star to measure the distortions, the correction is only useful within a small angular area centered on the guide star. The first part of this thesis presents a laboratory setup, which uses four guide stars to measure the turbulence-induced distortions and one deformable mirror to correct the most turbulent layer. With such a Layer-Oriented Ground-Layer Adaptive Optics (GLAO) system, the area of useful correction is significantly increased. The system is characterized in static and dynamic operation, and the influence of non-conjugated turbulent layers, the effect of brightness variations of the guide-stars and the impact of misalignments are studied. Furthermore, calibration strategies and the performance of the Kalman control algorithm are examined. The second part of this thesis focuses on SCIDAR measurements of the atmospheric turbulence above Mt. Graham. This dataset provides for the first time a statistical and thorough analysis of the vertical turbulence structure above the LBT site. Based on 16 nights of measurements, spread over one year, Mt. Graham appears to be an excellent site for an astronomical observatory. By extending an analytical model, describing the filtering of the turbulence-induced distortions by an AO system, we calculate performance expectations of the LINC-NIRVANA instrument. In particular, the optimal conjugation heights of the deformable mirrors are studied. Furthermore, we present a new method to measure the atmospheric turbulence near the ground with 40 times increased vertical resolution, compared to standard SCIDAR. First on-sky results demonstrate the power of this technique

The future of space imaging. Report of a community-based study of an advanced camera for the Hubble Space Telescope

The scientific and technical basis for an Advanced Camera (AC) for the Hubble Space Telescope (HST) is discussed. In March 1992, the NASA Program Scientist for HST invited the Space Telescope Science Institute to conduct a community-based study of an AC, which would be installed on a scheduled HST servicing mission in 1999. The study had three phases: a broad community survey of views on candidate science program and required performance of the AC, an analysis of technical issues relating to its implementation, and a panel of experts to formulate conclusions and prioritize recommendations. From the assessment of the imaging tasks astronomers have proposed for or desired from HST, we believe the most valuable 1999 instrument would be a camera with both near ultraviolet/optical (NUVO) and far ultraviolet (FUV) sensitivity, and with both wide field and high resolution options

Reducing adaptive optics latency using many-core processors

Atmospheric turbulence reduces the achievable resolution of ground based optical telescopes. Adaptive optics systems attempt to mitigate the impact of this turbulence and are required to update their corrections quickly and deterministically (i.e. in realtime). The technological challenges faced by the future extremely large telescopes (ELTs) and their associated instruments are considerable. A simple extrapolation of current systems to the ELT scale is not sufficient. My thesis work consisted in the identification and examination of new many-core technologies for accelerating the adaptive optics real-time control loop. I investigated the Mellanox TILE-Gx36 and the Intel Xeon Phi (5110p). The TILE-Gx36 with 4x10 GbE ports and 36 processing cores is a good candidate for fast computation of the wavefront sensor images. The Intel Xeon Phi with 60 processing cores and high memory bandwidth is particularly well suited for the acceleration of the wavefront reconstruction. Through extensive testing I have shown that the TILE-Gx can provide the performance required for the wavefront processing units of the ELT first light instruments. The Intel Xeon Phi (Knights Corner) while providing good overall performance does not have the required determinism. We believe that the next generation of Xeon Phi (Knights Landing) will provide the necessary determinism and increased performance. In this thesis, we show that by using currently available novel many-core processors it is possible to reach the performance required for ELT instruments

Abstracts on Radio Direction Finding (1899 - 1995)

The files on this record represent the various databases that originally composed the CD-ROM issue of "Abstracts on Radio Direction Finding" database, which is now part of the Dudley Knox Library's Abstracts and Selected Full Text Documents on Radio Direction Finding (1899 - 1995) Collection. (See Calhoun record https://calhoun.nps.edu/handle/10945/57364 for further information on this collection and the bibliography). Due to issues of technological obsolescence preventing current and future audiences from accessing the bibliography, DKL exported and converted into the three files on this record the various databases contained in the CD-ROM. The contents of these files are: 1) RDFA_CompleteBibliography_xls.zip [RDFA_CompleteBibliography.xls: Metadata for the complete bibliography, in Excel 97-2003 Workbook format; RDFA_Glossary.xls: Glossary of terms, in Excel 97-2003 Workbookformat; RDFA_Biographies.xls: Biographies of leading figures, in Excel 97-2003 Workbook format]; 2) RDFA_CompleteBibliography_csv.zip [RDFA_CompleteBibliography.TXT: Metadata for the complete bibliography, in CSV format; RDFA_Glossary.TXT: Glossary of terms, in CSV format; RDFA_Biographies.TXT: Biographies of leading figures, in CSV format]; 3) RDFA_CompleteBibliography.pdf: A human readable display of the bibliographic data, as a means of double-checking any possible deviations due to conversion

Advanced sparse optimization algorithms for interferometric imaging inverse problems in astronomy

In the quest to produce images of the sky at unprecedented resolution with high sensitivity, new generation of astronomical interferometers have been designed. To meet the sensing capabilities of these instruments, techniques aiming to recover the sought images from the incompletely sampled Fourier domain measurements need to be reinvented. This goes hand-in-hand with the necessity to calibrate the measurement modulating unknown effects, which adversely affect the image quality, limiting its dynamic range. The contribution of this thesis consists in the development of advanced optimization techniques tailored to address these issues, ranging from radio interferometry (RI) to optical interferometry (OI). In the context of RI, we propose a novel convex optimization approach for full polarization imaging relying on sparsity-promoting regularizations. Unlike standard RI imaging algorithms, our method jointly solves for the Stokes images by enforcing the polarization constraint, which imposes a physical dependency between the images. These priors are shown to enhance the imaging quality via various performed numerical studies. The proposed imaging approach also benefits from its scalability to handle the huge amounts of data expected from the new instruments. When it comes to deal with the critical and challenging issues of the direction-dependent effects calibration, we further propose a non-convex optimization technique that unifies calibration and imaging steps in a global framework, in which we adapt the earlier developed imaging method for the imaging step. In contrast to existing RI calibration modalities, our method benefits from well-established convergence guarantees even in the non-convex setting considered in this work and its efficiency is demonstrated through several numerical experiments. Last but not least, inspired by the performance of these methodologies and drawing ideas from them, we aim to solve image recovery problem in OI that poses its own set of challenges primarily due to the partial loss of phase information. To this end, we propose a sparsity regularized non-convex optimization algorithm that is equipped with convergence guarantees and is adaptable to both monochromatic and hyperspectral OI imaging. We validate it by presenting the simulation results