Aeronautical Engineering: A continuing bibliography, supplement 120

This bibliography contains abstracts for 297 reports, articles, and other documents introduced into the NASA scientific and technical information system in February 1980

COrE (Cosmic Origins Explorer) A White Paper

COrE (Cosmic Origins Explorer) is a fourth-generation full-sky, microwave-band satellite recently proposed to ESA within Cosmic Vision 2015-2025. COrE will provide maps of the microwave sky in polarization and temperature in 15 frequency bands, ranging from 45 GHz to 795 GHz, with an angular resolution ranging from 23 arcmin (45 GHz) and 1.3 arcmin (795 GHz) and sensitivities roughly 10 to 30 times better than PLANCK (depending on the frequency channel). The COrE mission will lead to breakthrough science in a wide range of areas, ranging from primordial cosmology to galactic and extragalactic science. COrE is designed to detect the primordial gravitational waves generated during the epoch of cosmic inflation at more than $3\sigma$ for $r=(T/S)>=10^{-3}$. It will also measure the CMB gravitational lensing deflection power spectrum to the cosmic variance limit on all linear scales, allowing us to probe absolute neutrino masses better than laboratory experiments and down to plausible values suggested by the neutrino oscillation data. COrE will also search for primordial non-Gaussianity with significant improvements over Planck in its ability to constrain the shape (and amplitude) of non-Gaussianity. In the areas of galactic and extragalactic science, in its highest frequency channels COrE will provide maps of the galactic polarized dust emission allowing us to map the galactic magnetic field in areas of diffuse emission not otherwise accessible to probe the initial conditions for star formation. COrE will also map the galactic synchrotron emission thirty times better than PLANCK. This White Paper reviews the COrE science program, our simulations on foreground subtraction, and the proposed instrumental configuration.Comment: 90 pages Latex 15 figures (revised 28 April 2011, references added, minor errors corrected

Trace gas concentration retrieval from short-wave infrared nadir sounding spaceborne spectrometers

The remote sensing of short wave infrared (SWIR) radiation reflected from the Earth allows to infer atmospheric trace gas concentrations by solving the inverse problem. The retrieval algorithm BIRRA (Beer InfraRed Retrieval Algorithm) has been developed at the DLR (Deutsches Zentrum f¨ur Luft- und Raumfahrt) Remote Sensing Technology Institute (IMF) since around 2005 and is one of multiple algorithms to infer molecular concentrations from calibrated radiance spectra. BIRRA’s forward model is based on the Generic Atmospheric Radiation Line-by-line Infrared Code (GARLIC) which has also been developed at the DLR-IMF. First, the BIRRA retrieved carbon monoxide (CO) columns from SCIAMACHY (SCanning Imaging Absorption spectroMeter for Atmospheric CHartographY) 2.3 μm observations from 2003–2011 were validated against eighteen stations from the ground-based networks TCCON (Total Carbon Column Observing Network) and NDACC (Network for the Detection of Atmospheric Composition Change). The BIRRA inferred CO concentrations were found to be ≈10% low biased which is in large agreement with other similar studies. Next, the latest updates from the radiative transfer code GARLIC were incorporated in BIRRA’s forward model and the physical results of both, the old (but validated) and the latest (updated) BIRRA algorithms were verified and found to be numerically consistent for SCIAMACHY input data. Subsequently, the forward model was extended by upgrading its capabilities with respect to spectroscopy, i.e., enhanced line models were incorporated in order to utilize latest spectroscopic information from line lists such as the SEOM–IAS (Scientific Exploitation of Operational Missions – Improved Atmospheric Spectroscopy). More specifically, ‘beyond Voigt’ line profiles were implemented and the impact of the SEOM–IAS spectroscopy was studied with respect to latest compilations of HITRAN (HIgh-resolution TRANsmission molecular absorption database) and GEISA (Gestion et Etude des Informations Spectroscopiques Atmosphériques) for a large set of SCIAMACHY measurements. It was found that the SEOM–IAS line data and corresponding line models have significant impact on the spectral fitting: the residuals become smaller and the retrieved CO concentrations are also slightly different. The same methodology was then applied to study the spectroscopic impact on CO from S5P/TROPOMI measurements. The impact of the SEOM–IAS spectroscopy revealed to be even more pronounced, in particular with respect to the fitting residuals and smaller retrieval errors (higher precision) of the CO and co-retrieved parameters. Overall, the TROPOMI results are in agreement with that found for SCIAMACHY. A subsequent part of the thesis examines instrument spectral response functions (ISRF), in particular appropriate parameterizations for the TROPOMI’s SWIR band responses. A first assessment with tabulated instrument profiles indicates that the parameterized variants can mimic the tabulated responses within ≈3–6 %, depending on the instrument model and spectral position. The positive impact of the SEOM–IAS spectroscopy on the spectral fitting residuals could also be identified with the parameterized response functions. Moreover, the presented instrument profiles are considered promising candidates for the description of responses from upcoming sensors due to their flexibility. Finally, the co-retrieval of aerosol parameters in the CO fit is presented. Based on a simple model for the aerosol optical thickness the feasibility to co-retrieve aerosol extinction was investigated. In this context two different inverse solvers, namely the ’classical’ nonlinear least squares and separable least squares, were examined with respect to convergence. First results show a stable CO retrieval for the separable least squares solver, however, the co-retrieved aerosol and reflectivity parameters indicate issues due to degeneracies. This thesis improved the retrieval of CO from SCIAMACHY observations. Moreover, the upgraded BIRRA algorithm successfully retrieved CO concentrations from cloud-free TROPOMI measurements. Many aspects investigated in this study are also relevant for the retrieval of other atmospheric constituents, such such CO2 or CH4. The study does hence provide a proven basis for further developments.Aus der Beobachtung reflektierter Sonnenstrahlung im kurzwelligen Infrarot (SWIR) können Spurengaskonzentrationen in der Erdatmosphäre abgeleitet werden, wobei die Lösung des inversen Problems eine Schätzung des wahren Atmosphärenzustands liefert. Die Inversionsmethode BIRRA (Beer InfraRed Retrieval Algorithm) ist einer von mehreren am DLR (Deutsches Zentrum für Luft- und Raumfahrt) am Institut für Methodik der Fernerkundung (IMF) entwickelten Algorithmen zur Bestimmung von Molekülkonzentrationen aus spektroskopischen Messungen. Das Vorwärtsmodell von BIRRA basiert auf dem ebenfalls am DLR-IMF entwickelten Generic Atmospheric Radiation Line-by-line Infrared Code (GARLIC). Am Anfang stand die Validierung der mit BIRRA abgeleiteten Kohlenmonoxid (CO) Gesamtsäulen aus SCIAMACHY (SCanning Imaging Absorption spectroMeter for Atmospheric CHartographY) Messungen im 2.3 μm Bereich. Dazu wurden die BIRRA Gesamtsäulen mit jenen der bodengebundenen Beobachtungsstationen der Netzwerke TCCON (Total Carbon Column Observing Network) and NDACC (Network for the Detection of Atmospheric Composition Change) im Zeitraum von 2003–2011 verglichen. Die mit BIRRA ermittelten CO Konzentrationen zeigen eine ≈10% negative Abweichung und stimmen mit den Ergebnissen ähnlicher Studien anderer Autoren weitgehend überein. Nach erfolgter Validierung wurden Neuerungen des Strahlungstransportmodells GARLIC in das BIRRA Vorwärtsmodell eingebaut und die Ergebnisse des aktualisierten Inversionsalgorithmus mit jenen des Vorgängers verglichen. Auf Basis von SCIAMACHY Daten wurde numerische Übereinstimmung der Ergebnisse festgestellt. Anschließend wurde das Vorwärtsmodell mit Blick auf die Verwendung neuester spektroskopischer Liniendaten, wie SEOM–IAS (Scientific Exploitation of Operational Missions – Improved Atmospheric Spectroscopy), erweitert. Um genauere Molekülabsorptionsquerschnitte berechnen zu können, musste das (klassische) Voigt-Absorptionslinienprofil erweitert werden. Der Einfluss der neuen Spektroskopie wurde zuerst auf Basis von SCIAMACHY Messungen untersucht und anhand von Vergleichsrechnungen auf Basis aktueller HITRAN (HIgh-resolution TRANsmission molecular absorption database) und GEISA (Gestion et Etude des Informations Spectroscopiques Atmosphériques) Daten bewertet. Es stellte sich heraus, dass die SEOM–IAS Liniendaten einen signifikanten Einfluss auf die Inversion haben: die Residuen werden kleiner und auch die abgeleiteten CO Konzentrationen unterscheiden sich leicht. Die gleiche Methodik wurde anschließend dazu verwendet, den Einfluss der Spektroskopie für das CO Retrieval aus TROPOMI Messungen zu bestimmen. Dabei zeigten sich die Auswirkungen noch deutlicher – signifikant kleinere Residuen und eine damit einhergehend höhere Genauigkeit (kleinere Fehler) der CO Säulen sowie der (mit-)abgeleiteten Parameter. Desweiteren besteht weitgehende Übereinstimmung mit den Resultaten der SCIAMACHY Studie. Ein weiterer Teil der Arbeit beschäftigt sich mit Instrumentenfunktionen (auch bekannt als Instrumentenprofile), speziell mit der Untersuchung einer passenden Parameterisierung der TROPOMI-Funktion im SWIR Band. Die tabellierten TROPOMI Instrumentenprofile können mit geeigneten Parameterisierungen gut modelliert werden. Darüber hinaus konnte der positive Einfluss der SEOM–IAS Spektroskopie auf die spektralen Residuen auch mit einem parameterisierten Instrumentenprofil nachgewiesen werden. Aufgrund der Flexibilität der vorgestellten Parameterisierungen könnten diese auch für zukünftige Sensoren zum Einsatz kommen. Abschließend wird der Einfluss von Aerosolen im CO Retrieval analysiert. Auf Basis einer einfachen Parameterisierung wurde versucht, die Extinktion bzw. die optische Tiefe (mit) zu bestimmen. In diesem Zusammenhang wurden auch der (klassische) nichtlineare Least Squares und der separierbare Least Squares hinsichtlich des Konvergenzverhaltens beim Lösen des inversen Problems untersucht. Erste Ergebnisse zeigen ein stabiles CO Retrieval unter Verwendung der separierbaren Least Squares Methode, wobei die (mit-)abgeleiteten Aerosol- und Reflektivitätsparameter auf Probleme durch Entartung hinweisen. Die vorliegende Arbeit hat gezeigt, wie das CO Retrieval aus SCIAMACHY Messungen verbessert werden kann. Mit dem weiterentwickelten BIRRA Code wurden darüberhinaus erfolgreich CO Konzentrationen aus wolkenfreien TROPOMI Messungen bestimmt. Viele Aspekte der Arbeit sind auch für die präzise Konzentrationsbestimmung anderer Moleküle wie CO2 oder CH4 von Bedeutung. Damit bietet die vorliegende Arbeit eine valide Grundlage für die Weiterentwicklung

A method for the estimation of p-mode parameters from averaged solar oscillation power spectra

A new fitting methodology is presented which is equally well suited for the estimation of low-, medium-, and high-degree mode parameters from $m$-averaged solar oscillation power spectra of widely differing spectral resolution. This method, which we call the "Windowed, MuLTiple-Peak, averaged spectrum", or WMLTP Method, constructs a theoretical profile by convolving the weighted sum of the profiles of the modes appearing in the fitting box with the power spectrum of the window function of the observing run using weights from a leakage matrix that takes into account both observational and physical effects, such as the distortion of modes by solar latitudinal differential rotation. We demonstrate that the WMLTP Method makes substantial improvements in the inferences of the properties of the solar oscillations in comparison with a previous method that employed a single profile to represent each spectral peak. We also present an inversion for the internal solar structure which is based upon 6,366 modes that we have computed using the WMLTP method on the 66-day long 2010 SOHO/MDI Dynamics Run. To improve both the numerical stability and reliability of the inversion we developed a new procedure for the identification and correction of outliers in a frequency data set. We present evidence for a pronounced departure of the sound speed in the outer half of the solar convection zone and in the subsurface shear layer from the radial sound speed profile contained in Model~S of Christensen-Dalsgaard and his collaborators that existed in the rising phase of Solar Cycle~24 during mid-2010

GAIA: Composition, Formation and Evolution of the Galaxy

The GAIA astrometric mission has recently been approved as one of the next two `cornerstones' of ESA's science programme, with a launch date target of not later than mid-2012. GAIA will provide positional and radial velocity measurements with the accuracies needed to produce a stereoscopic and kinematic census of about one billion stars throughout our Galaxy (and into the Local Group), amounting to about 1 per cent of the Galactic stellar population. GAIA's main scientific goal is to clarify the origin and history of our Galaxy, from a quantitative census of the stellar populations. It will advance questions such as when the stars in our Galaxy formed, when and how it was assembled, and its distribution of dark matter. The survey aims for completeness to V=20 mag, with accuracies of about 10 microarcsec at 15 mag. Combined with astrophysical information for each star, provided by on-board multi-colour photometry and (limited) spectroscopy, these data will have the precision necessary to quantify the early formation, and subsequent dynamical, chemical and star formation evolution of our Galaxy. Additional products include detection and orbital classification of tens of thousands of extra-Solar planetary systems, and a comprehensive survey of some 10^5-10^6 minor bodies in our Solar System, through galaxies in the nearby Universe, to some 500,000 distant quasars. It will provide a number of stringent new tests of general relativity and cosmology. The complete satellite system was evaluated as part of a detailed technology study, including a detailed payload design, corresponding accuracy assesments, and results from a prototype data reduction development.Comment: Accepted by A&A: 25 pages, 8 figure

Retrieval, Validations and Interpretation of Stratospheric Water Vapor Distributions from SCIAMACHY Lunar Occultation Measurements

Water vapor is a unique atmospheric component, its distribution directly influences the chemistry and dynamics in different parts of the atmosphere. Water vapor observations from satellite borne instruments provide information on its long term seasonal and inter-annual variabilities and are important for climate projections and predictions. In the polar stratosphere, the water vapor amounts control the polar vortex temperatures and the formation temperature of the polar stratospheric clouds (PSCs). Water vapor has a strong relationship with the circulation and transport features related to polar vortex and its amounts define the Formation and deposition of PSCs. SCanning Imaging Absorption spectroMeter for Atmospheric CHartographY (SCIAMACHY) aboard Envisat launched in 2002 has observed the Earth s atmosphere in nadir, limb and solar or lunar occultation geometry covering ultraviolet, visible and near ifrared (240-2830 nm) wavelength range at moderate spectral resolution. SCIAMACHY's measurements have provided total columns as well as vertical profiles of atmospheric constituents and climate parameters relevant to the ozone chemistry, air pollution and global climate change issues, from Troposphere upto the Mesosphere. This thesis contributes to exploit the lunar occultation spectra measured by SCIAMACHY at the local night time, with a latitudinal coverage of 56-89°S, to derive vertical stratospheric water vapor number density profiles in the altitude range of 17-50 km, from 2003 till 2010. The water vapor distributions are retrieved using the spectral window 1350-1420 nm in the near infrared region of the SCIAMACHY spectra. SCIATRAN version 3.0, a radiative transfer model and an inversion scheme based on optimal estimation (OE), is optimized and adapted for the retrieval. Within the inversion scheme, the residuals between the measured differential optical depths and the ones calculated by the forward model are in the order of 0.5%. The radiative transfer computation is performed using correlated-k method employing the exponential sum fitting of transmission function (ESFT) approximation instead of the detailed but computationally costly line by line (LBL) model. Since LBL is the most precise representative of reality, the ESFT database (pressure, temperature and coefficient grids) is optimized with an objective to achieve the closest agreement between the two approaches and to obtain a high quality retrieval product. The retrieval is observed to be highly sensitive to the numbers of coefficients in the ESFT grid. Extensive sensitivity studies and optimizations are performed for the key input parameters as slit function, signal to noise ratio, Tikhonov parameter and the climatological profiles to select their optimal values in the retrieval setting. To evaluate the quality of the retrieved lunar occultation water vapor product, validations are performed with collocated measurements from the satellite occultation instruments ACE-FTS and HALOE and the instruments measuring in limb geometry, MLS and MIPAS. In addition SCIAMACHY limb observations are also used for comparison. SCIAMACHY lunar occultation and ACE-FTS measurements agree within 7% on the average. With HALOE, the difference is around 5%. The validation of the coincident lunar occultation and the MLS measurements is exceptionally good with an agreement of 1.5-4% whereas that with MIPAS is in the range of 10%. The comparisons of the lunar occultation product with all the four instruments are found to be well within their reported biases. With the SCIAMACHY limb water vapor measurements, the differences are of the order of 4%. The validation results show that an excellent SCIAMACHY lunar occultation water vapor product is obtained. The dataset of water vapor distributions from SCIAMACHY lunar occultation measurements is expected to facilitate the understanding of physical and chemical processes in the southern mid-latitudes, the dynamical processes related to polar vortex and on the formation of PSCs, which can be studied through our product right at their onset as observed. The product will add as the southern hemispheric measurement coverage to the SCIAMACHY long term global water vapor time series

A Doppler Lidar system with preview control for wind turbine load mitigation

This dissertation focuses on the development of a system for wind turbine in order to mitigate the load from unstable wind speed. The work is divided into 2 main parts: a cost efficient Doppler wind Lidar system is developed based on a short coherence length laser system in combine with multiple length delayline concept; a preview pitch control is developed based on the design of a combination of 2 degree of freedom (2-DOF) feedback / feedforward control with a model predictive control