The Coronal Diagnostic Spectrometer for the solar and heliospheric observatory

The Coronal Diagnostic Spectrometer is designed to probe the solar atmosphere through the detection of spectral emission lines in the extreme ultraviolet wavelength range 150 – 800 . By observing the intensities of selected lines and line profiles, we may derive temperature, density, flow and abundance information for the plasmas in the solar atmosphere. Spatial and temporal resolutions of down to a few arcseconds and seconds, respectively, allow such studies to be made within the fine-scale structure of the solar corona. Futhermore, coverage of large wavelength bands provides the capability for simultaneously observing the properties of plasmas across the wide temperature ranges of the solar atmosphere.     

ESOP,a new Fabry-Perot spectrophotometer. Observations of the iron coronal lines in Puppis A

In this paper we present a new spectrophotometer ESOP (Expérience Spectroscopique d'Observation des Plasmas). We describe its general features and characteristics. We report the first spectrophotometric results on the Puppis A supernova remnant on the coronal iron line emission. These [FeXIV] observations were in the vicinity of the Eastern X-ray knot. We have observed at 30 scale. In appendices we describe in more details some specific technical points.Based on observations obtained at ESO-La Silla Observatory.     

基于无人机紫外与SAR的溢油遥感监测方法研究

溢油污染不仅会造成巨大的经济损失,而且给生态环境带来难以修复的破坏。准确、高效地监测海面溢油仍是当前亟需解决的问题。紫外传感器对油膜非常敏感,可快速发现,但存在误判;而SAR(SyntheticApertureRadar)溢油探测的精度较高,两者相结合可准确探测溢油。无人机平台可低成本地实现溢油快速应急响应,无人机载SAR和紫外传感器的载荷重量小,可同时集成于无人机上开展联合溢油探测,以满足业务化监测需求,此方面的研究尚未见有相关报道。本文拟研究溢油不同种类、厚度、在不同海洋环境条件下的紫外图像特征和SAR纹理特征、形状特征、散射特征,构建溢油特征数据库,并建立一种基于特征组合的溢油SAR与紫外联合探测方法;在此基础上研究对无人机数据获取模式和控制单元等的改造方案,进而实现溢油SAR和紫外图像的高效获取。     

A comparison of the ultraviolet to near-infrared spectral properties of Mercury and the Moon as observed by MESSENGER

Measurements of the disk-integrated reflectance spectrum of Mercury and the Moon have been obtained by the MESSENGER spacecraft. A comparison of spectra from the two bodies, spanning the wavelength range 220-1450 nm, shows that the absolute reflectance of Mercury is lower than that of the nearside waxing Moon at the same phase angle with a spectral slope that is less steep at visible and near-infrared wavelengths. We interpret these results and the lack of an absorption feature at a wavelength near 1000 nm as evidence for a Mercury surface composition that is low in ferrous iron within silicates but is higher in the globally averaged abundance of spectrally neutral opaque minerals than the Moon. Similar conclusions have been reached by recent investigations based on observations from both MESSENGER and Mariner 10. There is weak evidence for a phase-reddening effect in Mercury that is slightly larger in magnitude than for the lunar nearside. An apparent absorption in the middle-ultraviolet wavelength range of the Mercury spectrum detected from the first MESSENGER flyby of Mercury is found to persist in subsequent observations from the second flyby. The current model of space weathering on the Moon, which also presumably applies to Mercury, does not provide an explanation for the presence of this ultraviolet absorption.     

Martian phase function: Modeling the visible to near-infrared surface photometric function using HST-WFPC2 data

Images of Mars in the visible to near-infrared acquired from 1996 to 2005 using the Hubble Space Telescope WFPC2 have been used to model the martian surface photometric function at 502, 673, 953, and 1042 nm. These data range in spatial resolution from 12 to 70 km/pixel at the sub-Earth point, and in phase angle coverage from 0.34° to 40.5°. The WFPC2 images have been calibrated to radiance factor or I/F and projected to a cylindrical map for coregistration and comparison to similarly mapped spacecraft data sets of albedo, topography, thermal inertia, composition, and geology. We modeled the observed I/F as a function of phase angle using Minnaert, Lambert, lunar-Lambert, and Hapke photometric functions for numerous regions of interest binned into albedo units defined by Viking and TES albedo maps, and thermal-inertia units defined by TES thermal-inertia maps. Visibly opaque water-ice clouds and data acquired under high dust opacity conditions were excluded from the analysis. Our modeling suggests that under average to low atmospheric dust opacity conditions and over this range of phase angles, the photometric properties of the martian surface at 502, 673, 953, and 1042 nm are best modeled by lunar-Lambert functions with parameters derived for three surface units defined by low, moderate, and high TES bolometric albedos.     

DOAS Zenith Sky Observations: 1. BrO Measurements over Bremen (53°N) 1993–1994

Observations of stratospheric BrO over Bremen (53°N) are reported for winter and early spring periods of 1993 and 1993/94. The BrO was observed by ground-based near-UV absorption spectroscopy of sunlight scattered in the zenith. Differential slant column densities for solar zenith angles 90°/80° in the range of9× 10¹³ (detection limit) to 4.5×10¹⁴ molecules/cm² having a high day-to-day variability were found. For the majority of the measurements no significant difference was observed between the morning and evening behaviour of BrO. Exceptions are the morning measurements from the winter of 1992/93 where an accelerated production of BrO was observed. We believe the latter best to be explained by the early morning rapid photolysis of elevated amounts of photo-labile Br-reservoirs formed during the night. The largest differential slant column densities of BrO were measured in December 1993 when the temperatures at 30 hPa dropped below 205 K. This might be an indication of heterogeneous conversion of bromine compounds on sulfate and other aerosols.     

The influence of UV irradiation on the photoreduction of iron in the Southern Ocean

An iron enrichment experiment, EisenEx, was performed in the Atlantic sector of the Southern Ocean during the Antarctic spring of 2000. Deck incubations of open ocean water were performed to investigate the influence of ultraviolet B (UVB: 280–315 nm) and ultraviolet A (UVA: 315–400 nm) on the speciation of iron in seawater, using an addition of the radioisotopes ⁵⁹Fe(III) (1.25 nM) or ⁵⁵Fe(III) (0.5 nM). Seawater was sampled inside and outside the iron-enriched region. The radioisotopic Fe(II) concentration was monitored during daylight under three different light conditions: the full solar spectrum (total), total minus UVB, and total minus UVB+UVA. A distinct diel cycle was observed with a clear distinction between the three different light regimes. A clear linear relationship was found for the concentration of radioisotopic Fe(II) versus irradiance. UVB produced most of the Fe(II) followed by UVA and visible light (VIS: 400–700 nm), respectively. UVB produced 4.89 and 0.69 pM m² W⁻¹ radioisotopic Fe(II) followed by UVA with 0.33 and 0.10 pM m² W⁻¹ radioisotopic Fe(II) and VIS with 0.04 and 0.03 pM m² W⁻¹ radioisotopic Fe(II).     

Visible/near-infrared spectrogoniometric observations and modeling of dust-coated rocks

Interpretations of visible/near-infrared reflectance spectra of Mars are often complicated by the effects of dust coatings that obscure the underlying materials of interest. The ability to separate the spectral reflectance signatures of coatings and substrates requires an understanding of how their individual and combined reflectance properties vary with phase angle. Toward this end, laboratory multispectral observations of rocks coated with different amounts of Mars analog dust were acquired under variable illumination and viewing geometries using the Bloomsburg University Goniometer (BUG). These bidirectional reflectance distribution function (BRDF) data were fit with a two-layer radiative transfer model, which replicated BUG observations of dust-coated basaltic andesite substrates relatively well. Derived single scattering albedo and phase function parameters for the dust were useful in testing the model's ability to derive the spectrum of a “blind” substrate (unknown to the modeler) coated with dust. Subsequent tests were run using subsets of the BUG data restricted by goniometric or coating thickness coverage. Using the entire data set provided the best constraints on model parameters, although some reductions in goniometric coverage could be tolerated without substantial degradation. Predictably, the most thinly coated samples provided the best information on the substrate, whereas the thickest coatings best replicated the dust. Dust zenith optical thickness values ∼0.6-0.8 best constrain the substrate and coating simultaneously, particularly for large ranges of incidence or emission angles. The lack of sufficient angles can be offset by having a greater number and range of coatings thicknesses. Given few angles and thicknesses, few constraints can be placed concurrently on the spectral properties of the coating and substrate.     

Accurate and approximate calculations of Raman scattering in the atmosphere of Neptune

Raman scattering by H₂ in Neptune's atmosphere has significant effects on its reflectivity for λ<0.5 μm, producing baseline decreases of ∼20% in a clear atmosphere and ∼10% in a hazy atmosphere. However, few accurate Raman calculations are carried out because of their complexity and computational costs. Here we present the first radiation transfer algorithm that includes both polarization and Raman scattering and facilitates computation of spatially resolved spectra. New calculations show that Cochran and Trafton's (1978, Astrophys. J. 219, 756-762) suggestion that light reflected in the deep CH₄ bands is mainly Raman scattered is not valid for current estimates of the CH₄ vertical distribution, which implies only a 4% Raman contribution. Comparisons with IUE, HST, and groundbased observations confirm that high altitude haze absorption is reducing Neptune's geometric albedo by ∼6% in the 0.22-0.26 μm range and by ∼13% in the 0.35-0.45 μm range. A sample haze model with 0.2 optical depths of 0.2-μm radius particles between 0.1 and 0.8 bars fits reasonably well, but is not a unique solution. We used accurate calculations to evaluate several approximations of Raman scattering. The Karkoschka (1994, Icarus 111, 174-192) method of applying Raman corrections to calculated spectra and removing Raman effects from observed spectra is shown to have limited applicability and to undercorrect the depths of weak CH₄ absorption bands. The relatively large Q-branch contribution observed by Karkoschka is shown to be consistent with current estimates of Raman cross-sections. The Wallace (1972, Astrophys. J. 176, 249-257) approximation, produces geometric albedo ∼5% low as originally proposed, but can be made much more accurate by including a scattering contribution from the vibrational transition. The original Pollack et al. (1986, Icarus 65, 442-466) approximation is inaccurate and unstable, but can be greatly improved by several simple modifications. A new approximation based on spectral tuning of the effective molecular single scattering albedo provides low errors for zenith angles below 70° in a clear atmosphere, although intermediate clouds present problems at longer wavelengths.     

Size, albedo, and taxonomic type of potential spacecraft target Asteroid (10302) 1989 ML

The Amor-type near-Earth Asteroid (10302) 1989 ML has an “Earth-like” orbit (period 1.44 yr, eccentricity 0.14, inclination 4.4°), therefore the energy required to reach it from the Earth is relatively small making it a very attractive target for rendezvous missions. We have observed 1989 ML in the thermal-infrared using the Spitzer Space Telescope, and compared these data with optical and near-infrared observations. The Spitzer results imply a diameter of 0.28±0.05 km and a geometric albedo of 0.37±0.15; together with the reflectance spectrum they are consistent with the relatively rare E classification.