Error analysis for retrieval of Venus' IR surface emissivity from VIRTIS/VEX measurements

Venus' surface emissivity data in the infrared can serve to explore the planet's geology. The only global data with high spectral, spatial, and temporal resolution and coverage at present is supplied by nightside emission measurements acquired by the Visible and InfraRed Thermal Imaging Spectrometer VIRTIS-M-IR (1.0-5.1 μm) aboard ESA's Venus Express. A radiative transfer simulation and a retrieval algorithm can be used to determine surface emissivity in the nightside spectral transparency windows located at 1.02, 1.10, and 1.18 μm. To obtain satisfactory fits to measured spectra, the retrieval pipeline also determines auxiliary parameters describing cloud properties from a certain spectral range. But spectral information content is limited, and emissivity is difficult to retrieve due to strong interferences from other parameters. Based on a selection of representative synthetic VIRTIS-M-IR spectra in the range 1.0-2.3 μm, this paper investigates emissivity retrieval errors that can be caused by interferences of atmospheric and surface parameters, by measurement noise, and by a priori data, and which retrieval pipeline leads to minimal errors. Retrieval of emissivity from a single spectrum is shown to fail due to extremely large errors, although the fits to the reference spectra are very good. Neglecting geologic activity, it is suggested to apply a multi-spectrum retrieval technique to retrieve emissivity relative to an initial value as a parameter that is common to several measured spectra that cover the same surface bin. Retrieved emissivity maps of targets with limited extension (a few thousand km) are then additively renormalized to remove spatially large scale deviations from the true emissivity map that are due to spatially slowly varying interfering parameters. Corresponding multi-spectrum retrieval errors are estimated by a statistical scaling of the single-spectrum retrieval errors and are listed for 25 measurement repetitions. For the best of the studied retrieval pipelines, temporally varying interfering atmospheric parameters (cloud parameters, minor gas abundances) contribute errors in the order of 3%-10% of the true emissivity, depending on the surface window, the reference spectrum, and assuming statistical independence of the parameters. Temporally constant interfering parameters that spatially vary on a scale of 100 km (surface elevation, interfering emissivities) add 9%-16%. Measurement noise with a standard deviation of 10e-4 W/(m2 sr μm) leads to additional 1%-4%. Reasonable modifications of a priori mean values have negligible impacts. Retrieved maps are most reliable at 1.02 μm. There is an overall tendency for better results for cases with small cloud opacity, high surface elevation, high emissivity, and small observation angle, but this depends on the emissivity window, retrieval pipeline, and measurement repetition number. Calibration, preprocessing, and simulation errors can lead to additional errors. Based on the presented results, a subsequent paper will discuss emissivity data retrieval for a selected surface target

Multi-spectrum retrieval of Venus IR surface emissivity maps from VIRTIS/VEX nightside measurements at Themis Regio

Surface emissivity maps in the infrared can contribute to explore Venus’ geology. Nightside radiance spectra at Themis Regio acquired by the IR mapping channel of the Visible and InfraRed Thermal Imaging Spectrometer (VIRTIS-M-IR) aboard Venus EXpress (VEX) are used to derive emissivity data from the three accessible spectral surface windows at 1.02, 1.10, and 1.18 μm. The measured spectra are simulated by applying a full radiative transfer model. Neglecting geologic activity, a multi-spectrum retrieval algorithm is utilized to determine the emissivity maps of the surface target as parameter vectors that are common to many spectrally resolved images that cover this target. Absolute emissivity values are difficult to obtain due to strong interferences from other parameters. The true emissivity mean of the target cannot be retrieved, nor can the emissivity mean of a retrieved map be strictly preset. The retrieved map can exhibit trends with latitude and topography that are probably artificial. Once the trends have been removed in a post-processing step, it can be observed that the magnitude of the resulting spatial emissivity fluctuations around their mean value increases with increasing mean value. A linear transformation is applied that converts the de-trended map to exhibit a defined emissivity mean value called reference emissivity, here 0.5, yielding the ‘renormalized emissivity map’ with accordingly transformed fluctuations. It is verified that renormalized emissivity maps are largely independent of the emissivity mean before renormalization, of modifications to interfering atmospheric, surface, and instrumental parameters, and of selected details of the retrieval pipeline and data calibration and preprocessing. Extremely large emissivity retrieval errors due to imperfect or unconsidered forward model parameters are effectively avoided. If the absolute emissivity at a given bin of the target were known, the absolute emissivity map of the entire target could be computed according to the mentioned transformation, assuming absent true trends with latitude and topography. Until then, the renormalized emissivities are interpreted as spatial variations relative to the reference emissivity. They represent an important step toward the retrieval of absolute emissivities. Renormalized emissivity maps of Themis Regio at the three surface windows are determined from 64 measurement repetitions. Retrieval errors are estimated by a statistical evaluation of maps derived from various disjoint selections of spectra and using different assumptions on the interfering parameters. Double standard deviation errors for the three surface windows amount to 3%, 8%, and 4%, respectively, allowing geologic interpretation. A comparison to results from an earlier error analysis based on synthetic spectra shows that unconsidered time variations of interfering atmospheric parameters are a major error source. Spatial variations of the 1.02 μm surface emissivity of 20% that correspond to the difference between unweathered granitic and basaltic rocks would be easily detectable, but such variations are ruled out for the studied target area. Emissivity anomalies of up to 8% are detected at both 1.02 and 1.18 μm. At present sensitivity, no anomalies are identified at 1.10 μm, but anomalies exceeding the determined error level can be excluded. With single standard deviation significance, all three maps show interesting spatial emissivity variations

Lower atmosphere minor gas abundances as retrieved from Venus Express VIRTIS-M-IR data at 2.3 µm

Minor gas abundances in the lower atmosphere of Venus׳ southern hemisphere are investigated using spectroscopic nightside measurements recorded by the Visible and InfraRed Thermal Imaging Spectrometer aboard ESA’s Venus Express mission in the moderate spectral resolution infrared mapping channel (VIRTIS-M-IR, 1–5 µm, FWHM=17 nm). The entire usable data archive is utilized including only radiation spectra sampled at long detector exposure times (≥3.3 s) during eight Venus solar days between April 2006 and October 2008. Combined radiative transfer and retrieval techniques are applied for a simultaneous determination of total cloud opacity and H2O, CO, and OCS abundances from the 2.3 µm atmospheric transparency window that sounds the altitude range between about 30 and 45 km. A wavelength-dependent CO2 opacity correction is considered. Zonal averages of CO abundances at 35 km increase by about 35% from (22.9±0.8) ppmv at equatorial latitudes to (31.0±2.1) ppmv at 65 °S and then decrease to (29.4±2.4) ppmv at 80 °S The±figures refer to the statistical variability of retrieved abundances. In accordance with earlier results, the observed latitudinal variation of tropospheric CO is consistent with a Hadley cell-like circulation. Dawn side CO abundances at high latitudes are slightly smaller than dusk side values by about 7%. The latitudinal distribution of OCS at 35 km is anticorrelated with that of CO, ranging from about (1.15±0.2) ppmv at 65 °S to (1.60±0.2) ppmv at low latitudes (poleward decrease of 28%). Zonal averages of H2O abundances near 35 km slightly decrease toward the South Pole by about 10%, and the hemispheric average is (32.0±1.3) ppmv. A significant local time dependence of OCS and H2O is not observed. Detailed analyses of individual spectrum retrieval errors for different atmospheric models reveal that CO abundance results are reliable (error 4–7%), while H2O and OCS results have lower confidence (errors 30–47% and 41–86%, respectively). SO2 abundances cannot reliably be retrieved from VIRTIS-M-IR spectra

Sequence and mutational analysis of the devBCA gene cluster encoding a putative ABC transporter in the cyanobacterium Anabaena variabilis ATCC 29413

AbstractThe devBCA gene cluster (dev for development), shown to be essential for envelope formation in heterocysts of Anabaena sp. strain PCC 7120, was identified in the gene bank of a second heterocyst-forming strain, Anabaena variabilis ATCC 29413. Sequence and structural organization of the three genes, encoding subunits of a presumptive ABC transporter, were nearly identical in both strains. Mutants of A. variabilis defective in the devA gene were constructed. As devA mutants of Anabaena 7120, A. variabilis mutants were unable to grow on N2 as sole nitrogen source due to incomplete differentiation of heterocysts

Rosetta and 67P/Churyumov-Gerasimenko: a comet under observation

After a ten year’s expedition through the Solar system Europe’s comet chaser Rosetta arrived at comet 67 P/Churyumov- Gerasimenko in August 2014. Less than 100 kilometers from the nucleus the eleven orbiter payload instruments started to map and characterize the comet in great detail. In November 2014 Philae was the first robotic subsystem ever that landed on a cometary surface performing in situ measurements with ten instruments. The mission’s scientific program following the deployment of Philae is determined by the activity of the comet, which will increase as 67P approached perihelion in August 2015. This paper is a review article. It introduces the mission goals and profile. It gives an overview of some of the preliminary results of the mission. Selected results gained during the pre-landing phase of the subsystem Philae and the comet’s escort phases are discussed

Surface emissivity retrieval from VIRTIS/VEX data in the Quetzalpetlatl quadrangle on Venus based on the new MSR multi-spectrum retrieval technique

Surface emissivity is difficult and error-prone to retrieve from VIRTIS measurements of Venus’ nightside. A detailed radiative transfer forward model simulation is used to generate synthetic spectra for given atmospheric and surface parameters. The new MSR multi-spectrum retrieval technique is applied to retrieve atmospheric and surface parameters that allow the synthetic spectra to fit the measurements. The incorporation of expected spatial-temporal correlations between parameters describing a selection of contiguous measurements leads to much more reliable parameters, as does the retrieval of surface emissivity of a surface bin as a parameter that is common to measurements that repeatedly cover that bin, thereby neglecting geologic activity. The method is applied to Quetzalpetlatl quadrangle including the Lada Terra rise and the Quetzalpetlatl corona. This area combines corona-dominated rises, rifted volcanic rises, and large coronae structures. Retrieved emissivity at 1.02 μm is related to regional geologic units

Prediction of performance and cutter wear in rock TBM: Application to Koralm tunnel project

Excavation by Tunnel Boring Machines is the tunnelling method most frequently used nowadays in long infrastructural projects, in a wide range of geological conditions. In the last 40 years, many prediction models were developed to estimate TBM performance and cutter wear, using as input geological parameters. The research gives an overview of the existing penetration models for hard rock TBMs, identifies the most frequently used input parameters and summarizes the characteristics of the datasets on which the models are based on. Theoretical background is tested through the example of Koralm tunnel project, a 32.9-km-long base tunnel in Austria, in a 1000-m-long portion of the South tube in the construction lot KAT 2. The outcomes shows that the estimation of the penetration is reasonably accurate when applying models that are based on a database consistent with the project data, especially in terms of geology and typology of machine used in the excavation. The article proposes a design method for a system of TBM data analysis and prediction at the construction stage, based on a back-analysis process about machine data in different geological conditions. The methodology can be applied in any other project and the system is particularly useful in long tunnels, in which a continuous improvement of the ability of prediction can have an effective impact on time and costs

Berlin Reflectance Spectral Library (BRSL)

The Berlin Reflectance Spectral Library (BRSL) provides a collection of reflectance spectra between 0.3 and 17 µm. It was originally dedicated to support space missions to small solar system bodies. Meanwhile the library includes selections of biconical reflectance spectra for spectral data analysis of other planetary bodies as well. The library provides reference spectra of well-characterized terrestrial analogue materials and meteorites for interpretation of remote sensing reflectance spectra of planetary surfaces. We introduce the BRSL, summarize the data available, and access to use them for further relevant applications

Standortbedingungen und Beschäftigung in den Regionen West- und Ostdeutschlands : Ergebnisse des IAB-Betriebspanels 2006

"Der Bericht stellt erste Ergebnisse aus dem IAB-Betriebspanel 2006 für West- und Ostdeutschland vor. In den Kapiteln 2 und 3 werden einzelne wirtschaftliche Indikatoren sowie die Zufriedenheit der Betriebe mit ihrem Standort näher analysiert. Die Standortzufriedenheit wurde in der Befragung 2006 erstmals erhoben. Die regionale Betrachtung auf der Bundesländerebene steht bei beiden Kapiteln im Mittelpunkt. Für wichtige wirtschaftliche Indikatoren wie die Produktivität oder die Exportquote zeigt sich nach wie vor ein deutlicher West-Ost-Unterschied. Bei anderen Indikatoren wie der Investitionsintensität, dem technische Stand der Anlagen oder der Ertragslage sind zwischen West- und Ostdeutschland so gut wie keine Unterschiede mehr erkennbar. Die Zufriedenheit mit dem eigenen Standort ist bei den Betrieben vergleichsweise hoch. Die meisten Standortfaktoren, die für die Betriebe von Bedeutung sind, werden auch gut bewertet. Dies gilt im Aggregat. Bei einzelnen Faktoren signalisieren die Betriebe allerdings Handlungsbedarf. Während bei einigen wirtschaftlichen Indikatoren nach wie vor ein West-Ost-Gefälle zu erkennen ist, lässt sich bei der Standortzufriedenheit ein leichtes Süd-Nord-Gefälle feststellen. In Kapitel 4 wird auf die Beschäftigungsentwicklung und die dahinter stehenden Personalbewegungen eingegangen. Erstmals seit längerem ist die Beschäftigungsentwicklung wieder positiv. Auch die Bewegung auf dem Arbeitsmarkt hat zugenommen. Bedingt durch eine höhere Einstellungsrate ist die Labour-Turnover-Rate als Maß für die zwischenbetriebliche Mobilität angestiegen. Ebenso nimmt die beschäftigungsneutrale Personalfluktuation (Churning) wieder zu. Kapitel 5 widmet sich dem Schwerpunktthema der Befragung 2006: Betriebliche Bündnisse für Wettbewerb und Standortsicherung. Es zeigt sich, dass diese Bündnisse nur im Ausnahmefall abgeschlossen werden und sich somit die Intention der Tarifparteien bestätigt. Die Existenz eines Betriebs- oder Personalrates spielt für das Zustandekommen eine wichtige Rolle. Überdurchschnittlich häufig werden betriebliche Bündnisse in größeren Betrieben mit Haustarifvertrag vereinbart. Kapitel 6 beschreibt die aktuelle Ausbildungssituation aus der Sicht der Betriebe. Dabei wird besonderes Augenmerk auf das Ausbildungspotenzial gelegt - also auf Betriebe mit Ausbildungsberechtigung, die nicht ausbilden. In einer Längsschnittanalyse zeigt sich, dass ein Viertel der ausbildungsberechtigten Betriebe im Untersuchungszeitraum von 2000 bis 2005 tatsächlich gar nicht ausgebildet hat. Dabei handelt es sich vor allem um kleinere Betriebe. Drei Viertel der Betriebe hat - wenn auch zum Teil mit Unterbrechungen - ausgebildet. Kapitel 7 behandelt das Thema Arbeitszeit. Es wird ein genereller, nicht auf bestimmte Branchen beschränkter Trend zu einer längeren vertraglich vereinbarten Wochenarbeitszeit festgestellt. Gleichzeitig nimmt die Teilzeitarbeit zu. Auch im europäischen Vergleich ist Deutschland hinsichtlich der Teilzeitarbeit mit auf den vordersten Plätzen. Die Verbreitung von Arbeitszeitkonten hat nicht weiter zugenommen. Aber auch hier gehört Deutschland im europäischen Vergleich mit zu den Vorreitern. Langzeitkonten sind noch wenig verbreitet. Die Guthaben von Langzeitkonten sind bisher nur in wenigen Betrieben gegen Insolvenz gesichert. Im Anhang werden noch einige Indikatoren wie die Entwicklung von Betrieben und Beschäftigung, Entwicklung der Teilzeitbeschäftigung, Leiharbeit sowie befristeten und geringfügigen Beschäftigung in einer Tabellenübersicht dokumentiert." (Autorenreferat, IAB-Doku)Standortfaktoren, Beschäftigungsentwicklung, Standort - Zufriedenheit, labour turnover, Bündnis für Arbeit, Ausbildungsbereitschaft, Arbeitszeitentwicklung, Wochenarbeitszeit, Überstunden, Teilzeitarbeit, Arbeitszeitkonto, IAB-Betriebspanel, Tarifpolitik, Westdeutschland, Ostdeutschland, Bundesrepublik Deutschland

Advances in ITP – Therapy and Quality of Life – A Patient Survey

Current guidelines recommend glucocorticoids and splenectomy as standard 1(st) and 2(nd) line treatments for chronic immune thrombocytopenia (ITP). We sought to find out how German ITP-patients are treated with respect to these guidelines. Members of a patient support association ≥18 years with a self-reported history of chronic ITP>12 months were surveyed with a web-based questionnaire. 122 questionnaires were evaluated. 70% of patients had chronic ITP for more than 5 years and 20% an average platelet count of ≤30·10(9)/L. 41% of the patients reported haematomas or petechiae more than once or twice and up to 12 times or more per year and 17% oropharyngeal and nasal bleeds. 11% had been admitted to hospital during the last 12 months. 88% had received or currently receive glucocorticoids, 27% were splenectomised. IVIG had been given to 55%, rituximab to 22%, anti-D to 12%, ciclosporin to 7%, while complementary and alternative medical treatments had been used by 36%. 50 women responded to questions concerning pregnancy. 14 (28%) had been advised not to become pregnant. 23 reported pregnancies and 10 (44%) required treatment for their ITP during pregnancy. Glucocorticoids are the most common therapy for chronic ITP but complementary and alternative treatments already come second and less than ⅓ of patients are splenectomised. This and the frequent use of complementary medicines suggests patients' dissatisfaction with conventional approaches. Many patients receive off-label therapies. There is a major need for adequate counselling and care for pregnant ITP-patients