大气行星波影响低频电波吸收变化的机制

本文根据冬季中低纬低电离层中、低频（ＬＦ）电波振幅扰动与高纬平流层中大气行昨波活动密切相关的观测事实，分析研究了可能引起低电离层对ＬＦ电波吸收变化诸因素的作用后，提出了一种能较好地解释观测现象的物理机制，大气行星波可通过两种方式改变大气离化率ｑ，因而引起低电离层中电子密度Ｎ扰动，进而改变由Ｎ大小决定的电离层电波吸收值，结果导致ＬＦ电波振幅发生相应变化。文中给出了描述这一物理计算公式和某些计算结果。     

我国中低纬地区上空低电离层中的行星波

本文通过5年的电离层吸收观测资料与平流层增温事件对比及吸收资料的谱分析,得出以下几点初步结论:1)极区平流层增温事件的影响可能通过子午环流和行星波传播,经过5—9天后到达中低纬地区,从而引起那里的电离层吸收变化;2)冬季行星波沿子午方向的平均速度大约在10m/s到15m/s之间变化;3)全年均有周期为32天、18天、10天、8天和2天的行星波出现,它对大气湍流系数有明显影响。计算得出行星波扰动引起中层的NO浓度偏离未扰值可高达40%。      

A roadmap towards a space-based radio telescope for ultra-low frequency radio astronomy

The past two decades have witnessed a renewed interest in low frequency radio astronomy, with a particular focus on frequencies above 30 MHz e.g., LOFAR (LOw Frequency ARray) in the Netherlands and its European extension ILT, the International LOFAR Telescope. However, at frequencies below 30 MHz, Earth-based observations are limited due to a combination of severe ionospheric distortions, almost full reflection of radio waves below 10 MHz, solar eruptions and the radio frequency interference (RFI) of human-made signals. Moreover, there are interesting scientific processes which naturally occur at these low frequencies. A space or Lunar-based ultra-low-frequency (also referred to as ultra-long-wavelength, ULW) radio array would suffer significantly less from these limitations and hence would open up the last, virtually unexplored frequency domain in the electromagnetic spectrum.A roadmap has been initiated by astronomers and researchers in the Netherlands to explore the opportunity of building a swarm of satellites to observe at the frequency band below 30 MHz. This roadmap dubbed Orbiting Low Frequency Antennas for Radio Astronomy (OLFAR), a space-based ultra-low frequency radio telescope that will explore the Universe’s so-called dark ages, map the interstellar medium, and study planetary and solar bursts in the solar system and search them in other planetary systems. Such a radio astronomy system will comprise of a swarm of hundreds to thousands of satellites, working together as a single aperture synthesis instrument deployed sufficiently far away from Earth to avoid terrestrial RFI. The OLFAR telescope is a novel and complex system, requiring yet to be proven engineering solutions. Therefore, a number of key technologies are still required to be developed and proven. The first step in this roadmap is the NCLE (Netherlands China Low Frequency Explorer) experiment, which was launched in May 2018 on the Chinese Chang’e 4 mission. The NCLE payload consists of a three monopole antenna system for low frequency observations, from which the first data stream is expected in the second half of 2019, which will provide important feedback for future science and technology opportunities.In this paper, the roadmap towards OLFAR, a brief overview of the science opportunities, and the technological and programmatic challenges of the mission are presented.     

宇宙黑暗时代探路者——鸿蒙计划

低频射电探测任务构想——鸿蒙计划旨在利用多颗卫星绕月编队形成超长波天文观测阵列,在月球背面开展空间低频射电天文探测。其科学目标是高精度测量全天射电频谱,揭示宇宙黑暗时代与黎明的演化历史;实现首次高分辨率超长波巡天,打开最后一个电磁窗口;观测太阳和行星超长波活动,揭示空间环境相互作用规律。该任务将获得超长波频段全天空图像,获取超长波波段天文射电源的强度、频谱、分布等信息。这些科学数据对于探索宇宙黑暗时代和黎明时代、研究银河系星际介质、宇宙线起源与传播、河外射电星系、类星体和星系团的演化、太阳活动与行星磁场等,具有重要的科学价值。     

A drilling tool design and in situ identification of planetary regolith mechanical parameters

The physical and mechanical properties as well as the heat flux of regolith are critical evidence in the study of planetary origin and evolution. Moreover, the mechanical properties of planetary regolith have great value for guiding future human planetary activities. For planetary subsurface exploration, an inchworm boring robot (IBR) has been proposed to penetrate the regolith, and the mechanical properties of the regolith are expected to be simultaneously investigated during the penetration process using the drilling tool on the IBR. This paper provides a preliminary study of an in situ method for measuring planetary regolith mechanical parameters using a drilling tool on a test bed. A conical-screw drilling tool was designed, and its drilling load characteristics were experimentally analyzed. Based on the drilling tool-regolith interaction model, two identification methods for determining the planetary regolith bearing and shearing parameters are proposed. The bearing and shearing parameters of lunar regolith simulant were successfully determined according to the pressure-sinkage tests and shear tests conducted on the test bed. The effects of the operating parameters on the identification results were also analyzed. The results indicate a feasible scheme for future planetary subsurface exploration.     

Very low frequency interferometry for the Chang’E-2 project

Very low frequency interferometry among two astronomical experiments has been proposed and accepted for further study for the second phase of China’s lunar exploration programme (the Chang’E Programme), which is envisaged to operate a lander and a rover on the surface of the moon. This experiment is an interferometer experiment in the very low frequency (VLF, f < 15 MHz) regime of radio frequencies with at least degree-level angular resolution. The goals include observing solar storm activities, Coronal Mass Ejections, Auroral Kilometric Radiation, and planetary radiation in the solar system, studying the origin of Cosmic Rays, spectral properties of pulsars, surveying ionized hydrogen in the Galaxy, and exploring coherent radio emissions.     

1986年2月的高太阳活动研究──Ⅳ日地扰动事件耦合初析

利用光学、射电、软X射线和硬X射线观测资料,对1986年2月系列太阳爆发中最大的两个耀斑作相似与相异性的分析,解释它们近地空间效应的区别,对该系列太阳爆发事件和叠加在一起的地球事件作认证研究.      

Lower ionosphere response to external forcing: A brief review

There are two ways of external forcing of the lower ionosphere, the region below an altitude of about 100 km: (1) From above, which is directly or indirectly of solar origin. (2) From below, which is directly or indirectly of atmospheric origin. The external forcing of solar origin consists of two general factors – solar ionizing radiation variability and space weather. The solar ionization variability consist mainly from the 11-year solar cycle, the 27-day solar rotation and solar flares, strong flares being very important phenomenon in the daytime lower ionosphere due to the enormous increase of the solar X-ray flux resulting in temporal terminating of MF and partly LF and HF radio wave propagation due to heavy absorption of radio waves. Monitoring of the sudden ionospheric disturbances (SIDs – effects of solar flares in the lower ionosphere) served in the past as an important tool of monitoring the solar activity and its impacts on the ionosphere. Space weather effects on the lower ionosphere consist of many different but often inter-related phenomena, which govern the lower ionosphere variability at high latitudes, particularly at night. The most important space weather phenomenon for the lower ionosphere is strong geomagnetic storms, which affect substantially both the high- and mid-latitude lower ionosphere. As for forcing from below, it is caused mainly by waves in the neutral atmosphere, i.e. planetary, tidal, gravity and infrasonic waves. The most important and most studied waves are planetary and gravity waves. Another channel of the troposphere coupling to the lower ionosphere is through lightning-related processes leading to sprites, blue jets etc. and their ionospheric counterparts. These phenomena occur on very short time scales. The external forcing of the lower ionosphere has observationally been studied using predominantly ground-based methods exploiting in various ways the radio wave propagation, and by sporadic rocket soundings. All the above phenomena are briefly mentioned and some of them are treated in more detail.     

Connection between winter mesopause region temperatures and diurnal LF reflection height variations measured at Collm

Scale height, H, estimates are calculated from the decrease/increase of ionospheric virtual reflection heights of low-frequency (LF) radio waves at oblique incidence in suitably defined morning intervals around sunrise during winter months. The day-to-day variations of H qualitatively agree with daily mean temperature variations around 90 km from meteor radar measurements. Since mesospheric long-period temperature variations are generally accepted to be the signature of atmospheric planetary waves, this shows that LF reflection height measurements can be used for monitoring the dynamics of the upper middle atmosphere. The long-term variations of monthly mean H estimates have also been analysed. There is no significant trend, which is in agreement with other measurements of mesopause region temperature trends.     

基于中国岢岚地区法布里-珀罗干涉仪的风场及行星波观测特征

利用中国岢岚站（38.7°N,111.6°W）法布里-珀罗干涉仪2013年7月至2014年11月的水平风场数据,对87,97,250km风场长期变化和行星波特征进行了研究.通过分析年振荡（AO）和半年振荡（SAO）振幅相位,将午夜风场与HWM07数据对比发现:87km和97km处FPI纬向风变化趋势与HWM07相近,而经向风相位落后于HWM07,从振幅上看,HWM07振幅偏大;250km处风场月变化大,FPI与HWM07差异大,HWM07模式的准确性需进一步考虑太阳活动和行星际磁场的影响.利用Lomb-Scargle功率谱以及最小二乘谐波拟合提取了三个高度的行星波振幅,其特征表明87km和97km处纬向风16日波秋季及冬春季活动强,而6.5日波最强振幅出现在春季和秋季,在中间层顶附近两种行星波活动均较弱;250km处经向行星波活动略强于纬向,经向风不同周期带的行星波最强振幅主要出现在5-9月,与电离层f₀F₂振荡特性的研究结果一致.      

中层大气行星波的跨赤道传播

使用一个全球原始方程半谱模式,模拟了行星波的跨赤道传播。结果指出:冬半球对流层顶附近准定常行星波的幅度起伏和相位变化,可以造成中层大气行星波的跨赤道传播,并且在夏半球形成瞬变行星波。所得结果为中层大气行星波的跨赤道传播、夏半球行星波的形成和南北半球之间的耦合提供了一种物理机制。      

The problems of simulation of planetary systems accumulation processes

Evolution of a system consisting of a great number of bodies that are gravitationally interacting and aggregating in contacts is considered. Body motions take place in the gravitational field of a central massive body (Sun or planet) in the same plane and at the initial time of system evolution orbits of all bodies are circular. It is shown that during evolution of the protoplanetary cloud, ring zones of matter rarefaction and condensation develop. Development of the condensation zones leads to the formation of planets, the most part of which acquire a direct rotation about their axes. In the case under consideration, approximate agreement between the law of planetary distances and that of geometric progression takes place as it is observed in planetary and satellite systems. The formation of the terrestrial planets and Jovian planets has been simulated. The principal numerical results have been obtained through digital simulation of planetary accumulation.     

A new approach based on crater detection and matching for visual navigation in planetary landing

This paper provides an approach of crater detection and matching to visual navigation in planetary landing missions. The approach aims to detect craters on the planetary surface and match them to a landmark database during the descent phase of a planetary landing mission. Firstly an image region pairing method is proposed to detect the crater by using an image region feature detector. Then a WTA-rule is adopted to match the detected crater to the crater in database. To further reduce the false matching rate, an efficient method for reducing false matches using parameters of crater in 3-D database is proposed. Real images of planetary terrain and a semi-physical planetary landing simulation platform are utilized to test the performance of the approach, simulation results show the proposed approach is able to match the required number of craters to the database for pin-point planetary landing with a low rate of false detection and false matching, which will lead to an improved planetary landing precision.     

Time series modeling and analysis of trends of daily averaged ionospheric total electron content

A 10.7 cm solar radio flux F10.7, geomagnetic planetary equivalent amplitude (Ap index), and period variations were considered in this paper to construct a linear model for daily averaged ionospheric total electron content (TEC). The correlation coefficient of the modeled results and International GNSS Service (IGS) observables was approximately 0.97, which implied that the model could accurately reflect the realistic variation characteristics of the daily averaged TEC. The influences of the different factors on TEC and its characteristics at different latitudes were examined with this model. Results show that solar activity, annual and semiannual cycles are the three most important factors that affect daily averaged TEC. Solar activity is the primary determinant of TEC during periods with high solar activity, whereas periodic factors primarily contribute to TEC during periods with minimum solar activity. The extent of the influences of the different factors on TEC exhibits obvious differences at varying latitudes. The magnitude of the semiannual variation becomes less significant with the increase in latitude. Furthermore, a geomagnetic storm causes an increase in TEC at low latitudes and a decrease at high latitudes.     

地基行星大气掩星观测资料流程和数据整理

在中国火星探测萤火一号(YH-1)计划中, 包括了地基掩星观测反演火星大气的科研任务. 观测资料整理是反演流程的第一步. 本文描述了地基火星大气掩星观测处理软件系统的观测数据流程和观测资料整理模块,并详细介绍了观测资料整理模块的结构和功能, 其中包括时间系统转换、历表插值、坐标系变换、信号时延改正以及掩星平面建立. 利用行星数据系统公布的火星快车无线电科学数据和由SPICE得到的地球、火星历表以及火星快车的轨道数据, 结合本文的算法, 得到了一些实验结果.      

Study of the Moon and comparative planetology: Problems and perspectives

On the base of the comparative planetologic study of the Moon and terrestrial planets two fundamental features of their history and structure have been established.Firstly, shell-like structure of the terrestrial planets could be understood only in the terms of the heterogeneous accretion theory. At the final stages of major terrestrial planet formation the leading role belonged to the planetosimals of carbonaceous chondritic composition. Secondly, there are two types of the crust on the planetary surface. Their formation are considered to be independent and differing in the geological time. The primary planetary crust of predominantly feldspathic composition is considered to form during the pregeologic period at the final stage of planetary formation due to the impact-explosive processes. The hydrosphere and atmosphere is thought to appear contemporaneously. The basaltic planetary crust is forming later due to the radioactive decay and superimposed on the primary feldspathic crust.     

An introduction to the lunar and planetary science activities in Korea

Korea is planning a series of lunar space programs in 2020 starting with a lunar orbiter and a lander with a rover. Compared to other countries, Korea has a relatively brief history in space and planetary sciences. With the expected Korean missions on the near-term horizon and the relatively few Korean planetary scientists, Korea Institute of Geoscience and Mineral Resources (KIGAM) has established a new planetary research group focusing on development of prospective lunar instruments, analysis of the publicly available planetary data of the Moon, organizing nationwide planetary workshops, and initiating planetary educational programs with academic institutions. Korea has also initiated its own rocket development program, which could acquire a rocket-launch capability toward the Korean lunar mission. For the prospective Korea’s lunar science program, feasibility studies for some candidate science payloads have been started since 2010 for an orbiter and a lander. The concept design of each candidate instrument has been accomplished in 2012. It is expected that the development of science payloads may start by 2014 as Phase A. Not only developing hardware required for the lunar mission but also educational activities for young students are high priorities for Korea. The new plan of the Korean lunar mission can be successfully accomplished with international cooperative outreach programs in conjunction with internationally accessible planetary data system (PDS). This paper introduces the KIGAM’s international cooperative planetary research and educational programs and also summarizes other nationwide new developments for Korean lunar research projects at Kyung Hee University and Hanyang University.     

Revised planetary protection policy for solar system exploration

In order to control contamination of planets by terrestrial microorganisms and organic constituents, U.S. planetary missions have been governed by a planetary protection (or planetary quarantine) policy which has changed little since 1972. This policy has recently been reviewed in light of new information obtained from planetary exploration during the past decade and because of changes to, or uncertainties in, some parameters used in the existing quantitative approach. On the basis of this analysis, a revised planetary protection policy with the following key features is proposed: deemphasizing the use of mathematical models and quantitative analyses; establishing requirements for target planet/mission type (i.e., orbiter, lander, etc.) combinations; considering sample return missions a separate category; simplifying documentation; and imposing implementing procedures (i.e., trajectory biasing, cleanroom assembly, spacecraft sterilization, etc.) by exception, i.e., only if the planet/mission combination warrants such controls.     

Development of a thin section device for space exploration: Rock cutting mechanism

We have developed a rock cutting mechanism for in situ planetary exploration based on abrasive diamond impregnated wire. Performance characteristics of the rock cutter, including cutting rate on several rock types, cutting surface lifetime, and cut rock surface finish are presented. The rock cutter was developed as part of a broader effort to develop an in situ automated rock thin section (IS-ARTS) instrument. The objective of IS-ARTS was to develop an instrument capable of producing petrographic rock thin sections on a planetary science spacecraft. The rock cutting mechanism may also be useful to other planetary science missions with in situ instruments in which sub-sampling and rock surface preparation are necessary.     

Planetary radio astronomy from voyager

The Planetary Radio Astronomy instruments on Voyager 1 and 2 provided new, highly detailed measurements of several different kinds of strong, nonthermal radiation generated in the inner magnetospheres and upper ionospheres of Jupiter and Saturn. At Jupiter, an intense decameter-wavelength component (between a few tenths of a MHz and 39.5 MHz) is characterized by complex, highly organized structure in the frequency-time domain and by a strong dependence on the longitude of the observer and, in some cases, of Io. At frequencies below about 1 MHz there exists a (principally) kilometer-wavelength component of emission that is bursty, relatively broadbanded (typically covering 10 to 1000 kHz), and strongly modulated by planetary rotation. The properties of this component are consistent with a source confined to high latitudes on the dayside hemisphere of Jupiter. A second kilometric component is narrow-banded, relatively weak and exhibits a spectral peak near 100 kHz. The narrowband component also occurs periodically but at a repetition rate that is a few percent slower than that corresponding to the planetary rotation rate. This component is thought to originate at a frequency near the electron plasma frequency in the outer part of the Io plasma torus (8 to 10 R_J) and to reflect the small departures from perfect corotation experienced by plasma there.The Voyager instruments also detected intense, low frequency, radio emissions from the Saturn system. The Saturnian kilometric radiation is observed in a relatively narrow frequency band between 3 kHz and 1.2 MHz, is elliptically or circularly polarized, and is strongly modulated in intensity at Saturn's 10.66-hr rotation period. This emission is believed to be emitted in the right-hand extraordinary mode from regions near or in Saturn's dayside, polar, magnetospheric cusps. Variations in intensity at Saturn's rotation period may correspond to the rotation of a localized magnetic anomaly into the vicinity of the ionospheric footprint of the polar cusp. Variations in activity on time scales of a few days and longer seem to indicate that both the solar wind and the satellite Dione can also influence the generation of the radio emission.