Tethered-Satellite system (TSS): Preliminary results on the active experiment core equipment

Summary The first Tethered-Statellite System (TSS-1) Electrodynamic mission has been launched aboard the Space Shuttle STS-46 on July 31, 1992, as a joint mission between the United States and Italy. A 500 kg spherical Satellite (1.6 m diameter) attached to the Orbiter by a thin (0.24 cm), conducting, insulated wire (Tether), has been reeled upwards from the Orbiter payload bay to a distance of 257 m when the Shuttle was at a projected altitude of 300 km. ASI, the Italian Space Agency, had the responsibility for developing the reusable Satellite, while NASA had the responsibility for developing the Deployer system and the Tether, integrating the payload and providing transportation into space. One of the main scientific goals of this first mission was to demonstrate the possibility of energy conversion from mechanical to electrical by using a long Tether orbiting through the Earth's magnetic field. ASI designed and developed an active experiment, referred to as Core Equipment, in order to carry out this demonstration. The experiment used two Electron Generator Assemblies (EGAs), located on the Orbiter, to re-emit into the ionosphere as an electron beam the electrons collected on the Satellite from the ionosphere. Each EGA had the capability to emit an electron beam with a programmed intensity from 10 mA up to 750 mA with a resolution of 3 mA. The perveance of each EGA was 7.2 microperv, and the beam energy, up to 3 kV, was provided as part of the e.m.f. induced across the TSS due to its motion through the Earth's magnetic field. Other instruments provided current, voltage, and ambient-pressure measurements, and allowed, via a series of switches, different electrical configurations of the TSS. Moreover, the Core Equipment provided a dynamic package, to study the TSS dynamics, as a first goal, and to verify the possibility of using the TSS Satellite as a platform for future experiments in the microgravity field. The expected voltage across the TSS was estimated to be 5 kV for a full Tether deployment of 20 km. During the mission, and due to unforeseenable reasons, the Tether deployment achieved was only of 257 m. Despite this limitation, there is evidence that the experiment was working nominally in the very low-voltage range across the TSS. This result strongly increases the confidence in the possibility of high-voltage operation of the electrodynamic TSS, as the Tether deployment will achieve the 20 km, as expected in the future reflight. The paper describes the experiment, and reports some preliminary results achieved during the first mission. Paper presented at the 6th Cosmic Physics National Conference, Palermo, 3–7 November 1992.     

TSS core equipment I.—Electrodynamic package and rationale for system electrodynamic analysis

Summary The first Tethered-Satellite System (TSS-1) Electrodynamic mission has been launched aboard the Space Shuttle STS-46 on July 31, 1992, as a joint mission between the United States and Italy. A 500 kg, spherical Satellite (1.6 m diameter), attached to the Orbiter by a thin (0.24 cm), conducting, insulated wire (Tether), has been reeled upwards from the Orbiter payload bay to a distance of 256 m, rather than the expected 20 km, when the Shuttle was at a projected altitude of 300 km. ASI, the Italian Space Agency, had the responsibility for developing the reusable Satellite, while NASA had the responsibility for developing the Deployer system and the Tether, integrating the payload and providing transportation into space. One of the main scientific goals of this first mission is to demonstrate the possibility of energy conversion from mechanical to electrical by using a long Tether orbiting through the Earth's magnetic field. ASI designed and developed an active experiment, referred to as Core Equipment, in order to carry out this demonstration, and to support all the scientific investigations related to the study of the TSS electrodynamic interactions with the Earth's ionosphere. The experiment uses two Electron Generator Assemblies (EGAs), located on the Orbiter, to re-emit into the ionosphere, as an electron beam, the electrons collected on the Satellite from the ionosphere. Other instruments provide current, voltage, and ambient pressure measurements, and allow, via a series of switches, different electrical configurations of the TSS. The Core Equipment was innovative for space experiments in general and Shuttle experiments in particular. In fact, it was the first flight in which the Shuttle has been used as an integral part of the experiment and not only as an observing platform. It was the first mission with an integrated approach to science, will all the instrumentation and their operative modes selected to characterize the electric properties of the TSS.     

EUV-FUV spectroscopy of TSS optical Phenomena

Summary We propose to use the IEH (International Ultraviolet Hitchhiker), a multidisciplinary facility (Astronomy, Solar System, Earth's atmosphere) to be mounted on the Shuttle pallet as a Hitchhiker flight opportunity, in order to obtain 2D images in the EUV-FUV ((400÷1300) ?) of the optical phenomena occurring in the neighborhood of the TSS satellite. These peculiar phenomena, not detectable during the first TSS mission, are primarily due to the interaction of a high-potential conductive body with the surrounding ionospheric plasma. Paper presented at the V Cosmic Physics National Conference, S. Miniato, November 27–30, 1990.     

鄱阳湖总悬浮物浓度高光谱定量模型

以鄱阳湖为研究对象,利用地物波谱仪在湖区进行高光谱测量和同步的水体采样实验,通过研究鄱阳湖水体的光谱反射率特征和实测总悬浮物(TSS)浓度之间的关系,建立了TSS浓度的遥感定量模型.结果表明,由于悬浮物的反射作用出现双峰特征,红光与近红外部分波段是TSS的敏感区域,敏感性红光波段大于近红外波段;一阶微分处理的593nm处一阶导数数据和TSS浓度的一元二次方程为反演的最佳模型.研究成果可为今后卫星遥感大面积监测鄱阳湖TSS浓度奠定基础.     

与哈姆林甜橙果实内在品质主要参数同步相关的特征光谱研究

基于光谱分析的甜橙内在品质检测技术近年得到较快发展,但目前采用的大多为单一品质指标的光谱分析,而甜橙果实品质往往取决于果实多项品质指标的共同作用。本研究的目的在于研究甜橙果实反射光谱与果实内在品质的相关性,筛选与哈姆林甜橙果实多个品质指标同步相关的特征光谱,为建立甜橙果实在内品质的实时检测技术提供依据。以哈姆林甜橙(Citrus sinensis (L) cv. Hamlin sweet orange)成熟果实为试材,逐个果实进行果实反射光谱和果实可溶性固形物(TSS)、柠檬酸、维生素C(Vc)含量和固酸比等在内品质主要参数的分析,对所获数据采用Excel,Spss Statg和View SpecPro软件进行统计与分析。结果表明,哈姆林甜橙果实TSS、固酸比和Vc均与波长988 nm近红外光反射光谱呈极显著或显著正相关,相关系数分别为0.387**,0.440**和0.309*,TSS和固酸比与该波长反射率的最佳拟合方程分别为y＝13.957x+5.405和y＝75.120x+37.256;可见光429 nm光谱二阶导数与TSS和Vc呈显著和极显著正相关,相关系数分别为0.350 72*和0.386 9**。波长944 nm近红外光谱倒数对数与固酸比呈显著正相关(r＝0.304*)。试验结果为柑桔果实内在品质主要参数的同步、快速无损检测奠定了基础。     

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根据ITER装置对CTB盒技术性能的要求,对CTB盒中冷屏的支撑部件进行了结构和传热的分析和设计。对结构形式的选择、结构强度的理论计算和支撑结构总的热损失进行了设计和计算,用ANSYS软件对该结构的非线性接触结构-热耦合问题进行了仿真分析。研究结果表明,球支撑结构既能够满足系统对支撑的结构安全要求,在有压接触情况下的漏热量符合ITER设计文集的规定。     

Detection of quasitrapezoidal frequency and amplitude modulation

It has been proposed that the detection of frequency modulation (FM) of sinusoidal carriers can be mediated by two mechanisms; a place mechanism based on FM-induced amplitude modulation (AM) in the excitation pattern, and a temporal mechanism based on phase locking in the auditory nerve. The temporal mechanism appears to be "sluggish" and does not play a role for FM rates above about 10 Hz. It also does not play a role for high carrier frequencies (above about 5 kHz). This experiment provided a further test of the hypothesis that the effectiveness of the temporal mechanism depends upon the time spent close to frequency extremes during the modulation cycle. Psychometric functions for the detection of AM and FM were measured for two carrier frequencies, 1 and 6 kHz. The modulation waveform was quasitrapezoidal. Within each modulation period, P, a time Tss was spent at each extreme of frequency or amplitude. The transitions between the extremes, with duration Ttrans had the form of a half-cycle of a cosine function. The modulation rate was 2, 5, 10, or 20 Hz, giving values of P of 500, 200, 100, and 50 ms. TSS varied from 0 ms (sinusoidal modulation) up to 160, 80, 40, or 20 ms, for rates of 2, 5, 10, and 20 Hz, respectively. The detectability of AM was not greatly affected by modulation rate or by the value of TSS, except for a slight improvement with increasing TSS for the lowest modulation rates; this was true for both carrier frequencies. For FM of the 6-kHz carrier, the pattern of results was similar to that found for AM, which is consistent with an excitation-pattern model of FM detection. For FM of the 1-kHz carrier, performance improved markedly with increasing TSS, especially for the lower FM rates; there was no change in performance with TSS for the 20-Hz modulation rate. The results are consistent with the idea that detection of FM of a 1-kHz carrier is partly mediated by a sluggish temporal mechanism. That mechanism benefits from greater time spent at frequency extremes of the modulation cycle for rates up to 10 Hz.     

CO oxidation facilitated by robust surface states on Au-covered topological insulators

Surface states--the electronic states emerging as a solid material terminates at a surface--are usually vulnerable to contaminations and defects. The robust topological surface state(s) (TSS) on the three-dimensional topological insulators provide a perfect platform for exploiting surface states in less stringent environments. Employing first-principles density functional theory calculations, we demonstrate that the TSS can play a vital role in facilitating surface reactions by serving as an effective electron bath. We use CO oxidation on gold-covered Bi(2)Se(3) as a prototype example, and show that the robust TSS can significantly enhance the adsorption energy of both CO and O(2) molecules, by promoting different directions of static electron transfer. The concept of TSS as an electron bath may lead to new design principles beyond the conventional d-band theory of heterogeneous catalysis.     

Neutron dosimetry in low-earth orbit using passive detectors

This paper summarizes neutron dosimetry measurements made by the USF Physics Research Laboratory aboard US and Russian LEO spacecraft over the past 20 years using two types of passive detector. Thermal/resonance neutron detectors exploiting the 6Li(n,T) alpha reaction were used to measure neutrons of energies <1 MeV. Fission foil neutron detectors were used to measure neutrons of energies above 1 MeV. While originally analysed in terms of dose equivalent using the NCRP-38 definition of quality factor, for the purposes of this paper the measured neutron data have been reanalyzed and are presented in terms of ambient dose equivalent. Dose equivalent rate for neutrons <1 MeV ranged from 0.80 microSv/d on the low altitude, low inclination STS-41B mission to 22.0 microSv/d measured in the Shuttle's cargo bay on the highly inclined STS-51F Spacelab-2 mission. In one particular instance a detector embedded within a large hydrogenous mass on STS-61 (in the ECT experiment) measured 34.6 microSv/d. Dose equivalent rate measurements of neutrons >1 MeV ranged from 4.5 microSv/d on the low altitude STS-3 mission to 172 microSv/d on the ~6 year LDEF mission. Thermal neutrons (<0.3 eV) were observed to make a negligible contribution to neutron dose equivalent in all cases. The major fraction of neutron dose equivalent was found to be from neutrons >1 MeV and, on LDEF, neutrons >1 MeV are responsible for over 98% of the total neutron dose equivalent. Estimates of the neutron contribution to the total dose equivalent are somewhat lower than model estimates, ranging from 5.7% at a location under low shielding on LDEF to 18.4% on the highly inclined (82.3 degrees) Biocosmos-2044 mission.     

CALET Results after Three Years on Orbit on the International Space Station

Physics of Atomic Nuclei - The CALorimetric Electron Telescope (CALET) is an astroparticle physics experiment installed on the International Space Station since August 2015. The CALET mission was...     

Thermal Spin Squeezing as a Signature of Thermal Global Entanglement in Heisenberg Models

We study thermal spin squeezing (TSS) and thermal global entanglement (TGE) in a general Heisenberg spin chain, in the presence of Dzyaloshinskii-Moriya interaction and an external magnetic field. We derive an inequality associating the squeezing parameter and the global concurrence, which establishes (TSS) as a signature of (TGE). The inequality reduces to equality for particular symmetric chains which also associates TSS with bipartite entanglement in such systems. We also check the results by presenting two numerical examples.     

The Shuttle Potential and return electron experiment (SPREE)

Summary The Shuttle Potential and Return Electron Experiment (SPREE) was designed and fabricated for flight as part of the joint NASA/Agenzia Spaziale Italiana Tethered Satellite System (TSS-1) mission. The SPREE is a complex instrument package designed to measure ion and electron particle flux and wave-particle interactions. The SPREE flight hardware consists of two multiangular electrostatic analyzer units, two rotary tables, a data processing unit, a particle correlator experiment, and two data recording units. The electrostatic analyzers measure both electrons and ions, in an energy range from 10 eV to 10 keV and simultaneously over an angular fan of (100×10) degrees. These units are mounted on the rotary tables to provide a 2π steradian field of view out of the Orbiter's payload bay. To assess negative charging of the Orbiter with respect to the ambient plasma, ion data from the analyzers are processed real time by an on-board algorithm operating within the data processing unit. The particle correlator experiment determines wave-particle interactions in the frequency range 0–10 MHz for electrons and from 0–10 kHz for ions. SPREE operated successfully throughout the TSS-1 mission. Examples of the data returned by the SPREE are shown.     

Thermal Spin Squeezing as a Signature of Thermal Global Entanglement in Heisenberg Models

We study thermal spin squeezing (TSS) and thermal global entanglement (TGE) in a general Heisenberg spin chain, in the presence of Dzyaloshinskii-Moriya interaction and an external magnetic field. We derive an inequality associating the squeezing parameter and the global concurrence, which establishes (TSS) as a signature of (TGE). The inequality reduces to equality for particular symmetric chains which also associates TSS with bipartite entanglement in such systems. We also check the results by presenting two numerical examples.     

Gaussian Density Matrices: Quantum Analogs of Classical States

We study quantum analogs of classical situations, i.e. quantum states possessing some specific classical attribute(s). These states seem quite generally, to have the form of gaussian density matrices. Such states can always be parametrized as thermal squeezed states (TSS). We consider the following specific cases: (a) Two beams that are built from initial beams which passed through a beam splitter cannot, classically, be distinguished from (appropriately prepared) two independent beams that did not go through a splitter. The only quantum states possessing this classical attribute are TSS. (b) The classical Cramer's theorem was shown to have a quantum version (Hegerfeldt). Again, the states here are Gaussian density matrices. (c) The special case in the study of the quantum version of Cramer's theorem, viz. when the state obtained after partial tracing is a pure state, leads to the conclusion that all states involved are zero temperature limit TSS. The classical analog here are gaussians of zero width, i.e. all distributions are δ functions in phase space.     

Energy spectrum of iron nuclei measured inside the MIR space craft using CR-39 track detectors

We have exposed stacks of CR-39 plastic nuclear track detectors inside the MIR space craft during the EUROMIR95 space mission for almost 6 months. Over this long period a large number of tracks of high LET events was accumulated in the detector foils. The etching and measuring conditions for this experiment were optimized to detect tracks of stopping iron nuclei. We found 185 stopping iron nuclei inside the stack and identified their trajectories through the material of the experiment. Based on the energy-range relation the energy at the surface of the stack was determined. These particles allow the determination of the low energy part of the spectrum of iron nuclei behind shielding material inside the MIR station.     

Manipulating Nonlinear Photocurrent from Interlayer Coupling in Bilayer Metamaterials for Polarized Terahertz Generation

Polarized terahertz (THz) wave generation is of great significance for chiral and anisotropic sensing applications. However, how to manipulate amplitude, polarization, and ellipticity of the THz generation is still a fundamental challenge. Herein, polarized THz wave generation is achieved from a bilayer metamaterial consisting of T-shaped structure (TSS) and split resonator rings (SRRs) by combining Maxwell and hydrodynamic equations. The elliptically polarized THz wave can be synthetized directly from horizontally and vertically polarized THz components due to the orthogonal nonlinear photocurrents along the arm-directions of TSS and SRRs, respectively. Besides, the ellipticity and the orientation angle of the THz polarization ellipse can be modulated by the twist angle between the SRRs and TSS layers. The maximum ellipticity can reach 0.34 while the orientation angle is tunable from −0.45 to 0.48π by tuning the twist angle. This work proposes an interlayer coupling method for the polarized THz sources based on metamaterials in potential circular dichroism and chiral sensing applications.     

The ACES/PHARAO space mission

Proposed in 1997, the ACES/PHARAO experiment is a space mission in fundamental physics with two atomic clocks on the International Space Station, a network of ultra-stable clocks on the ground, and space-to-ground time transfer systems. The ACES flight instruments are near completion and launch in space is planned for the first half of 2017 for a mission duration of three years. A key element of the satellite payload is a cold-atom clock designed for microgravity environment, PHARAO, operating with laser-cooled cesium atoms. Here we first report on the design and tests of the PHARAO flight model, which is now completed and ready for launch. We then briefly present the status of development of the other instruments of the ACES payload, the Space Hydrogen Maser, the microwave time-transfer system (MWL), and the laser time transfer ELT.     

星上定标光源LED长期工作的稳定性

为配合空间相机研制任务,对LED作为星上定标光源的可行性进行了研究。介绍了试验用LED的结构。从理论上分析了深能级的产生对LED发光效率的影响,引入阿仑尼斯模型对LED的衰减进行了分析。根据任务需要,对LED进行了老化试验,利用积分球法测量LED的相对发光强度,定时监测,得到LED发光强度随时间变化的曲线及趋势。根据试验结果,研究和分析了LED长时间工作的稳定性。试验结果显示,老化初期LED相对发光强度变化明显,经过250h的持续工作后,变化趋于平稳。3000h后LED相对发光强度总的衰减量约为3%,期间峰值变化量小于1.5%,满足星上定标的要求。给出了试验过程中LED的衰减情况,作为校正参考。最后根据实验结果对LED的寿命进行了理论的估算。     

拓扑绝缘体的普适电导涨落

拓扑绝缘体因其无能量耗散的拓扑表面输运而备受关注, 揭示拓扑表面态因其 的贝利相位而产生的拓扑输运现象, 将有助于拓扑绝缘体相关器件的应用开发. 本文回顾了普适电导涨落(UCF) 揭示拓扑绝缘体奇异输运性质的研究进展. 通过调控温度、角度、门电压、垂直磁场和平行磁场等外部参量, 实现了对拓扑绝缘体的UCF 效应的系统研究, 证实了拓扑绝缘体中二维UCF 的输运现象, 并通过尺寸标度规律获得了UCF 的拓扑起源的实验证据, 讨论了拓扑表面态的UCF 的统计对称规律. 从而实现了对拓扑绝缘体UCF 效应的较为完整的理解.