Gravity field models from kinematic orbits of CHAMP,GRACE and GOCE satellites

The aim of our work is to generate Earth’s gravity field models from GPS positions of low Earth orbiters. Our inversion method is based on Newton’s second law, which relates the observed acceleration of the satellite with forces acting on it. The observed acceleration is obtained as numerical second derivative of kinematic positions. Observation equations are formulated using the gradient of the spherical harmonic expansion of the geopotential. Other forces are either modelled (lunisolar perturbations, tides) or provided by onboard measurements (nongravitational perturbations). From this linear regression model the geopotential harmonic coefficients are obtained.     

Whole lichen thalli survive exposure to space conditions: results of Lithopanspermia experiment with Aspicilia fruticulosa

The Lithopanspermia space experiment was launched in 2007 with the European Biopan facility for a 10-day spaceflight on board a Russian Foton retrievable satellite. Lithopanspermia included for the first time the vagrant lichen species Aspicilia fruticulosa from Guadalajara steppic highlands (Central Spain), as well as other lichen species. During spaceflight, the samples were exposed to selected space conditions, that is, the space vacuum, cosmic radiation, and different spectral ranges of solar radiation (λ?≥?110, ≥200, ≥290, or ≥400?nm, respectively). After retrieval, the algal and fungal metabolic integrity of the samples were evaluated in terms of chlorophyll a fluorescence, ultrastructure, and CO(2) exchange rates. Whereas the space vacuum and cosmic radiation did not impair the metabolic activity of the lichens, solar electromagnetic radiation, especially in the wavelength range between 100 and 200?nm, caused reduced chlorophyll a yield fluorescence; however, there was a complete recovery after 72?h of reactivation. All samples showed positive rates of net photosynthesis and dark respiration in the gas exchange experiment. Although the ultrastructure of all flight samples showed some probable stress-induced changes (such as the presence of electron-dense bodies in cytoplasmic vacuoles and between the chloroplast thylakoids in photobiont cells as well as in cytoplasmic vacuoles of the mycobiont cells), we concluded that A. fruticulosa was capable of repairing all space-induced damage. Due to size limitations within the Lithopanspermia hardware, the possibility for replication on the sun-exposed samples was limited, and these first results on the resistance of the lichen symbiosis A. fruticulosa to space conditions and, in particular, on the spectral effectiveness of solar extraterrestrial radiation must be considered preliminary. Further testing in space and under space-simulated conditions will be required. Results of this study indicate that the quest to discern the limits of lichen symbiosis resistance to extreme environmental conditions remains open.     

Monitoring coastal sea level using reflected GNSS signals

A continuous monitoring of coastal sea level changes is important for human society since it is predicted that up to 332 million people in coastal and low-lying areas will be directly affected by flooding from sea level rise by the end of the 21st century. The traditional way to observe sea level is using tide gauges that give measurements relative to the Earth’s crust. However, in order to improve the understanding of the sea level change processes it is necessary to separate the measurements into land surface height changes and sea surface height changes. These measurements should then be relative to a global reference frame. This can be done with satellite techniques, and thus a GNSS-based tide gauge is proposed. The GNSS-based tide gauge makes use of both GNSS signals that are directly received and GNSS signals that are reflected from the sea surface. An experimental installation at the Onsala Space Observatory (OSO) shows that the reflected GNSS signals have only about 3 dB less signal-to-noise-ratio than the directly received GNSS signals. Furthermore, a comparison of local sea level observations from the GNSS-based tide gauge with two stilling well gauges, located approximately 18 and 33 km away from OSO, gives a pairwise root-mean-square agreement on the order of 4 cm. This indicates that the GNSS-based tide gauge gives valuable results for sea level monitoring.     

Coronal index of solar activity – Solar-terrestrial research

The purpose of this paper is to introduce a coronal index of solar activity (CI) as computed from ground-based observations of the green coronal line intensities (Fe?xiv; 530.3 nm). This index, expressed in W s^?1, is derived for the period 1939–1998 and belongs to the class of ground-based indices used to study solar activity and its influence on the heliosphere. The smoothed peak solar cycle intensity of the CI increased monotonically during the period of research. On the other hand, comparative studies have shown relatively good agreement with similar solar indices. CI can be used to study, among other things, the rotation of the Sun as a star, and long-term, intermediate- and short-term periodicities. The CI is inferred from a homogeneous coronal data set that can be used to study such topics as the 2D distribution of the green corona and photospheric/chromospheric activity, the differential rotation of the emission green corona, and the relationship between the green corona and cosmic rays.     

不仅仅是奢侈品

跨界合作奢侈酒店横空山世奢侈品品牌个个都热衷于跨界合作,从LV的麻将牌到Hermes的自行车,从Dior的手机到Gucci的汽车。一个个看似毫无关联却又异常和谐的奢侈品陆续出现在公众视野中,有了奢侈品的加入,任何东西都能成为奢华的象征。因此,当奢侈品大鳄们踏足酒店业时,我们并不感到惊讶,这一切都是那么顺其自然。     

一种飞-续-飞随机谱的编制方法及软件

本文介绍了一种飞-续-飞随机谱的编制方法和软件。它以空测的重心过载数据为基础,经过数据处理后,建立对应于每个飞行任务的Markov矩阵。并调整统计平均后的Markov矩阵以保证可得到一个不中断的过载序列。然后从矩阵中抽取半循环序列,构成飞-续-飞随机谱。本文中讨论了矩阵中半循环的随机抽取方法,给出了应用实例。