On the role of tidal winds in the descending of the high type of sporadic layer (Esh)

As the prevailing tidal winds in the E region are generated by heating mechanisms, the dynamics of Es layers impacted by solar tides is a relevant theme in the space weather studies. This paper aims to identify the tidal wind component involved in the mechanism of formation and descending of the high type of sporadic layer (Es_h). The Es_h layers observed at altitudes between around 120 and 150 km in the Brazilian low latitude stations of Jataí and São José dos Campos during the months of April, June, September and December of 2016 are used in this analysis. The height variability and altitude descent of the Es_h layers are analyzed from the h′Es parameter obtained by ionosonde data. In this study, the observational data are compared with the simulations generated by an extended version of the Ionospheric E-Region Model (MIRE). At higher altitudes in the E region, the results show that the prevailing tidal pattern and wind direction controlling the Es_h layer formation and descent are different depending on month: (a) in April and June the zonal wind component and the associated semidiurnal tidal oscillations prevail, with some differences in terms of time of occurrence and descending speeds, and (b) in September and December the diurnal tidal periodicities become dominant, and both the meridional and zonal wind components seem to control the descending of the Es_h layers. Since the role of the tidal periodicities and wind directions changed depending on the month, the results suggest a possible seasonal tidal wind pattern, which is not well understood from the present study but requires further investigation. Other relevant aspects of the observations and the modeling are highlighted and discussed.     

阻尼网特性数值模拟

依靠经验公式和工程估算等传统方法,无法对阻尼网性能进行精确评估.为确定阻尼网压力损失系数和降湍性能,采用计算流体力学方法,结合适当的边界条件,对阻尼网进行了模拟.使用数值模拟能够得到不同开孔率阻尼网在不同雷诺数、不同入射方向、不同目数的损失系数,与试验结果更为接近,在30°~45°大角度入射时得到的损失系数更为精确;在入射气流与阻尼网平面呈一定夹角时,阻尼网后的气流压力和速度呈现脉动趋势,传播距离大约为100d;在雷诺数小于40时流动保持层流状态,扰动传播距离为50d,此时降湍效果最好,随雷诺数增加,扰动传播距离增加至400d;在流动未失稳时,开孔率越低,降湍效果越明显,开孔率低于0.5时流动容易失稳;开孔率保持不变,随目数增加阻尼网损失系数增加明显,降湍能力提升.因此可以根据数值模拟结果选择阻尼网的最优参数.     

复杂管网系统未知信息调节阀的一种瞬变建模方法

关键调节阀信息缺失是制约复杂管网系统可建模的重要因素。通过对调节阀建模研究的分类和总结，得出了多数调节阀的流量特性曲线均处于等百分比与线性之间的结论；进而针对结构和节流特性均未知的调节阀，提出了一种利用信息已知的基准阀门模型和有限的系统试验数据进行建模的方法。对核心机试验台气路系统中2个未知信息调节阀的建模与仿真表明:在常温0~1 400 s、低温0~1 240 s两种工况下，选用3种不同基准阀门模型仿真结果的差别低于10%，2个调节阀在47组件气路全系统仿真中的流量曲线与试验曲线之间的平均误差在15%以内，系统下游两支路的压强仿真曲线与试验曲线之间的最大误差低于15%，为解决此类问题提供了一种有效的建模方案。      

Regional gravity field model in Pakistan area from the combination of CHAMP,GRACE and ground data using least squares collocation: A case study

This study describes a methodology of recovery of the Earth’s gravity field from CHAMP and GRACE satellites data in Pakistan using least squares collocation (LSC) based downward continuation technique. The CHAMP height anomalies and GRACE gravity disturbances derived from the observed satellite data have been used in combination solution using LSC with observed gravity values at the Earth surface. The combined covariance functions of height anomalies and/or gravity disturbances at satellite altitudes and observed gravity anomalies at Earth surface have been used as the basis for combination and downward continuation solution. The variance of predicted gravity anomalies from GRACE gravity disturbances is relatively lower than the corresponding results of gravity anomalies from CHAMP height anomalies. This fact may be attributed partly to the amplification of noise and partly to the unstable inverse transformation process of height anomalies to gravity anomalies. The impact of data error variance has been studied in the context of smoothing and noise reduction in the final solution of downward continuation using least squares collocation. The raising of data error suppresses the noise and as a result a smooth final solution is obtained. The prediction results appear to be dependent on the quality of data and goodness of combined covariance function, which are fairly comparable for the CHAMP and GRACE data. The recovered gravity field from satellite data appears to contribute mainly to medium and long wavelength parts of total gravity field spectrum. Due to flexibility of data handling in least squares collocation, this procedure is applicable to any observable of gravity field being at different altitudes and with different data spacing.     

Effects of solar activity variations on the low latitude topside nighttime ionosphere

We have studied the topside nighttime ionosphere of the low latitude region using data obtained from DMSP F15, ROCSAT-1, KOMPSAT-1, and GUVI on the TIMED satellite for the period of 2000–2004, during which solar activity decreased from its maximum. As these satellites operated at different altitudes, we were able to discriminate altitude dependence of several key ionospheric parameters on the level of solar activity. For example, with intensifying solar activity, electron density was seen to increase more rapidly at higher altitudes than at lower altitudes, implying that the corresponding scale height also increased. The density increased without saturation at all observed altitudes when plotted against solar EUV flux instead of F10.7. The results of the present study, as compared with those of previous studies for lower altitudes, indicate that topside vertical scale height increases with altitude and that, when solar activity increases, topside vertical scale height increases more rapidly at higher altitudes than at lower altitudes. Temperature also increased more rapidly at higher altitudes than at lower altitudes as solar activity increased. In addition, the height of the F2 peak was seen to increase with increasing solar activity, along with the oxygen ion fraction measured above the F2 peak. These results confirm that the topside ionosphere rises and expands with increasing solar activity.     

The atmospheric cosmic- and solar energetic particle radiation environment at aircraft altitudes

Galactic cosmic rays interact with the solar wind, the earth's magnetic field and its atmosphere to produce hadron, lepton and photon fields at aircraft altitudes. In addition to cosmic rays, energetic particles generated by solar activity bombard the earth from time to time. These particles, while less energetic than cosmic rays, also produce radiation fields at aircraft altitudes which have qualitatively the same properties as atmospheric cosmic rays. We have used a code based on transport theory to calculate atmospheric cosmic-ray quantities and compared them with experimental data. Agreement with these data is seen to be good. We have then used this code to calculate equivalent doses to aircraft crews. We have also used the code to calculate radiation doses from several large solar energetic particle events which took place in 1989, including the very large event that occurred on September 29^th and 30^th of that year. The spectra incident on the atmosphere were determined assuming diffusive shock theory.     

A new window on the cosmos: The Stratospheric Observatory for Infrared Astronomy (SOFIA)

The Stratospheric Observatory for Infrared Astronomy (SOFIA) is a joint US/German Project to develop and operate a gyrostabilized 2.5-m telescope in a Boeing 747-SP. This observatory will allow astronomical observations from 0.3 μm to sub-millimeter wavelengths at stratospheric altitudes as high as 45,000 ft where the atmosphere is not only cloud-free, but largely transparent at infrared wavelengths. The dynamics and chemistry of interstellar matter, and the details of embedded star formation will be key science goals. In addition, SOFIA’s unique portability will enable large-telescope observations at sites required to observe transient phenomena and location specific events. SOFIA will offer the convenient accessibility of a ground-based telescope for servicing, maintenance, and regular technology upgrades, yet will also have many of the performance advantages of a space-based telescope. Initially, SOFIA will fly with nine first-generation focal plane instruments that include broad-band imagers, moderate resolution spectrographs that will resolve broad features from dust and large molecules, and high resolution spectrometers capable of studying the chemistry and detailed kinematics of molecular and atomic gas. First science flights will begin in 2010, leading to a full operations schedule of about 120 8–10 h flights per year by 2014. The next call for instrument development that can respond to scientifically exciting new technologies will be issued in 2010. We describe the SOFIA facility and outline the opportunities for observations by the general scientific community with cutting edge focal plane technology. We summarize the operational characteristics of the first-generation instruments and give specific examples of the types of fundamental scientific studies these instruments are expected to make.     

A new reeling technique for very long extension scanning in the stratosphere

A balloon borne winching system has been developed for extending a very long tether with payload down into the stratosphere and recovering it; this has been flight proven by being carried to an altitude of 40 km, lowering a 62 kg stratospheric photochemistry experiment 12 km at a descent velocity of ～6–8 m/sec and recovering it at comparable velocities. During the first flight, data gave no evidence of dynamic instabilities due to the system or the stratospheric interactions. The future utility of this payload is discussed with attention to the design factors that bound the range of performance of this type of system.     

基于GNSS的高轨卫星定位技术研究

利用全球卫星导航系统(GNSS)进行导航定位具有全球、全天候、实时和高精度的优点,应用于高地球轨道(HEO)卫星的定位,能够提供精确的轨道和姿态确定,并且可以克服目前主要利用地面测控系统对HEO卫星进行定位的设备复杂、投资高等缺点,使得自主导航成为可能.本文对利用GNSS的高轨卫星定位相关技术进行了研究,分析了单一GNSS系统和多个GNSS组合系统的卫星可见性、动态性和几何精度因子(GDOP).通过仿真分析表明,利用组合GNSS系统并通过提高GNSS接收机灵敏度的方法,可以解决GNSS进行HEO卫星定位的相关问题,并能保证HEO卫星定位精度的要求.      

Balloon-borne,high-altitude gravimetry

Gravity measurements from a high-altitude balloon can verify global and upward-continued gravity models. A gravimeter suspended beneath a balloon is in a dynamic, and largely unpredictable, environment sensing accelerations due to gravity and balloon motions. Independent measurements of balloon motions using inertial navigation data combined with ground tracking data will allow for separation of balloon-induced accelerations from gravitational accelerations. Analysis of these data must estimate: 1) vertical gravimeter accelerations due to motion and gravity, 2) horizontal velocity to estimate the Eötvös effect, and 3) gravimeter position for comparison with gravity models. The first engineering test flight occurred on 11 October 1983, during the seasonal wind reversal and was very successful. Flight duration was approximately seven hours, with two hours of data collected at each of 30 km and 26 km altitudes. The results include gravity estimates, design criteria for future flights and feasibility analysis for vertical gravity profiles during ascent and descent.     

Chemical composition measurements of the atmosphere of Jupiter with the Galileo Probe mass spectrometer.

The Galileo Probe entered the atmosphere of Jupiter on December 7, 1995. Measurements of the chemical and isotopic composition of the Jovian atmosphere were obtained by the mass spectrometer during the descent over the 0.5 to 21 bar pressure region over a time period of approximately 1 hour. The sampling was either of atmospheric gases directly introduced into the ion source of the mass spectrometer through capillary leaks or of gas, which had been chemically processed to enhance the sensitivity of the measurement to trace species or noble gases. The analysis of this data set continues to be refined based on supporting laboratory studies on an engineering unit. The mixing ratios of the major constituents of the atmosphere hydrogen and helium have been determined as well as mixing ratios or upper limits for several less abundant species including: methane, water, ammonia, ethane, ethylene, propane, hydrogen sulfide, neon, argon, krypton, and xenon. Analysis also suggests the presence of trace levels of other 3 and 4 carbon hydrocarbons, or carbon and nitrogen containing species, phosphine, hydrogen chloride, and of benzene. The data set also allows upper limits to be set for many species of interest which were not detected. Isotope ratios were measured for 3He/4He, D/H, 13C/12C, 20Ne/22Ne, 38Ar/36Ar and for isotopes of both Kr and Xe.     

局部地区高空磁场的计算方法

本文用曲面样条函数表示地磁场及其水平梯度在地面上的分布, 从而使A.J.Zmuda提出的计算高空磁场的方法更加简便。本文还给出了借助于局部地区地磁场的球谐分析, 计算高空磁场的方法。      

Systems for long duration flights

This paper describes the systems for long duration flights developed in Japan for scientific observations. Much efforts have been expended to evolve systems for long duration flights in Japan, by controlling the balloon trajectories with a knowledge of wind pattern at high altitudes over Japan. These systems called “Cycling Balloon”, “Boomerang Balloon” and “New Boomerang Balloon” have been successfully used for the observations by keeping the balloons close to the balloon station.“Relay Balloon” is another system to extend the telemetry range by using an additional balloon as a relay station to link the telemetry from the main balloon.Some detailes of the exhaust valve, ascent meter and automatic level control devices used for the balloon control are also described in the paper.     

Flight safety implications of the extreme solar proton event of 23 February 1956

There is considerable speculation about the effects at aircraft altitudes resulting from extreme solar proton events. The ground level event (GLE) of 23 February 1956 (GLE 5), remains the largest solar proton event of the neutron monitor era in terms of its influence on count rates at monitors near sea level. During this GLE the count rate was increased by as much as 4760% (15-min average) at the Leeds monitor relative to the count rate from galactic cosmic radiation (GCR). Two modern models of the event cumulative solar proton spectrum for this event, a 6-parameter fit in energy and a 4-parameter Band fit in rigidity, are compared with 1-h of GCR at solar minimum. While effective doses calculated with CARI-7A for both models at low geomagnetic cutoff rigidities are indeed high when compared with GCR and can exceed recommended exposure limits, both GLE spectra exhibit a much stronger dependence on cutoff rigidity than GCR, and a larger fraction of the dose from neutrons. At locations with cutoff rigidities above 4.2 and 6.4?GV, respectively, the GLE effective doses are smaller than the GCR hourly dose. At locations with cutoff rigidities above about 4?GV, GCR was the dominant source of exposure in 10?h or less at all altitudes examined. This suggests that if a similar event occurs in the future, low- and mid-latitude flights at modern jet flight altitudes could be well-protected by Earth’s magnetic field.     

月球引力转弯软着陆的制导控制研究

对于月球引力转弯软着陆过程 ,采用反馈线性化方法 ,对高度和速度信息分别设计了跟踪制导控制律 ,并应用微分几何的有关理论证明了这两种跟踪制导控制系统的李雅普诺夫稳定性。此外 ,根据软着陆系统推力、燃料和状态的约束条件 ,给出了引力转弯着陆过程初始条件的可达集合。最后给出的软着陆跟踪制导实例 ,只需要测得斜向距离、速度和姿态角度信息。这种制导方法测量简单 ,适于低成本的软着陆任务。     

Analysis of tape tether survival in LEO against orbital debris

The low earth orbit (LEO) environment contains a large number of artificial debris, of which a significant portion is due to dead satellites and fragments of satellites resulted from explosions and in-orbit collisions. Deorbiting defunct satellites at the end of their life can be achieved by a successful operation of an Electrodynamic Tether (EDT) system. The effectiveness of an EDT greatly depends on the survivability of the tether, which can become debris itself if cut by debris particles; a tether can be completely cut by debris having some minimal diameter. The objective of this paper is to develop an accurate model using power laws for debris-size ranges, in both ORDEM2000 and MASTER2009 debris flux models, to calculate tape tether survivability. The analytical model, which depends on tape dimensions (width, thickness) and orbital parameters (inclinations, altitudes) is then verified with fully numerical results to compare for different orbit inclinations, altitudes and tape width for both ORDEM2000 and MASTER2009 flux data.     

Ionospheric losses of Venus in the solar wind

The nature of ionospheric losses from Venus is of essential importance for understanding the ionosphere dynamics of this unmagnetized planet. A plausible mechanism that can explain the escape of charged particles involves the solar wind interaction with the upper atmospheric layers of Venus. The hydrodynamic approach proposed for plasma expansion in the present study comprises two populations of positive ions and the neutralizing electrons, which interact with the solar wind electrons and protons. The fluid equations describing the plasma are solved numerically using a self-similar approach. The behavior of plasma density, velocity, and electric potential, as well as their reliance upon solar wind parameters have been examined. It is found that for noon midnight sites, the oxygen ion-to-electron relative density may be the main factor to enhance the ionic loss. However, the other parameters, like hydrogen density and solar wind density and velocity seem to do not stimulate the runaway ions. For lower dawn-dusk region, the plasma are composed of hydrogen and oxygen ions as well as electrons, but for higher altitudes only hydrogen ions and electrons are encountered. All ionic densities play an important role either to reduce or boost the ionic loss. The streaming solar wind velocity has no effect on the plasma escaping for lower altitudes, but it reduces the expansion at higher altitudes.     

Power supplies for long duration balloon flights

Long duration balloon flights require more electrical power than can be carried in primary batteries. This paper provides design information for selecting rechargeable batteries and charging systems. Solar panels for recharging batteries are discussed, with particular emphasis on cells mounting suitable for balloon flights and panel orientation for maximum power collection. Since efficient utilization of power is so important, modern DC to DC power conversion techniques are presented.On short flights of 1 day or less, system designers have not been greatly concerned with battery weight. But, with the advent of long duration balloon flights using superpressure balloons, anchor balloon systems, and RACOON balloon techniques, power supplies and their weight become of prime importance. The criteria for evaluating power systems for long duration balloon flights is performance per unit weight. Instrumented balloon systems have flown 44 days. For these very long duration flights, batteries recharged from solar cells are the only solution. For intermediate flight duration, say less than 10 days, the system designer should seriously consider using primary cells.     

Shock protection of penetrator-based instrumentation via a sublimation approach

It is often necessary for space-borne instrumentation to cope with substantial levels of shock acceleration both in the initial launch phase, as well as during entry, descent and landing in the case of planetary exploration. Current plans for a new generation of penetrator-based space missions will subject the associated on-board instrumentation to far greater levels of shock, and ways must therefore be found to either ruggedize or else protect any sensitive components during the impact phase. In this paper, we present an innovative method of shock protection that is suited for use in a number of planetary environments, based upon the temporary encapsulation of said components within a waxy solid which may then be sublimated to return the instrument back to its normal operation. We have tested this method experimentally using micromachined silicon suspensions under applied shock loads of up to 15,000g, and found that these were able to survive without incurring damage. Furthermore, quality factor measurements undertaken on these suspensions indicate that their mechanical performance remains unaffected by the encapsulation and subsequent sublimation process.