火星进入气体辐射加热研究进展

针对飞行器进入火星大气时气体辐射加热对防热设计带来不确定性，在简述火星探测和气体辐射研究的发展历程的基础上，对火星进入气体辐射加热研究的进展进行综述。首先，针对火星大气环境描述了气体辐射加热的概念和问题由来。其次，重点综述了近年来火星进入气体辐射加热基础模型的数值和试验研究进展，其中包括：热化学非平衡气体动力学、气体辐射特性和辐射传输的计算模型与方法等数值研究；地面测试设备、试验技术和模拟火星大气环境的气体辐射测量与验证等试验研究。再次，综述了流动辐射耦合和后体气体辐射加热等火星进入器设计方面开展的研究。最后，对未来火星进入气体辐射加热研究进行了展望，提出了研究建议。     

静电电磁脉冲辐射场诱发针-球电极结构放电试验

针对当前国内外诱发静电放电（ESD）研究较少的实际情况，为了解自然环境下静电放电辐射场诱发放电的基本特性，进一步分析诱发放电的特征规律，建立了大气条件下诱发放电试验系统。主要采取理论分析、试验验证的方式，对静电放电辐射场诱发针-球电极结构放电的基本规律进行摸索，初步得出了诱发放电的基本规律。研究结果表明：在外界条件一定的情况下，随着辐射场强的不断增大，放电重复频率不断增大；在辐射场强一定的情况下，随着高压源电压的不断增大，诱发放电重复频率不断增大；在外界环境条件一定的情况下，能够确定该条件下的诱发放电唯一阈值。这些试验规律的取得，为真空条件下的诱发放电特性研究提供了试验方法和理论依据，对开展航天器运行环境中的诱发放电研究和防护方法设计具有重要意义。     

Short-term periodicities in the downward longwave radiation and their associations with cosmic ray and solar interplanetary data

In this study downward longwave (LW) atmospheric radiation data for the period of 2014–2020 were used to search for short-term periodicities using fast Fourier transform (FFT). Several local peaks in the power spectrum density were found and established. The time series exhibits a series of significant peaks (exceeding the 95% confidence limit), such as at 273 days, 227 days, 200 days, 178 days, 157 days, 110 days, 120 days, 87 days, 73 days, 53–56 days, 35–30 days, 25–27 days, 21 days, 13 days, and 9–10 days.Moreover, cosmic ray data from KACST muon detector and the Oulu neutron monitor, as well as the data for the solar radio flux at 10.7 cm (F10.7 cm), Dst index, and solar wind speed for the same period as the LW data, were used to look for common cyclic variations and periodicities matching those found in the LW radiation. This was done to investigate the possible effect of the solar activity parameters on LW radiation. Several common periodicities were observed in the spectra of all the variables considered, such as 227 days, 154–157 days, 25–27 days, and 21 days. Some of the periodicities found in the LW radiation spectrum can be attributed to the modulation of the cosmic ray intensity by solar activity. Others are attributed to the disturbances in the interplanetary magnetic field. Based on the spectral results, we suggest that the solar signals may directly or indirectly affect the variations of the downward longwave radiation, which in turn may affect climate change.     

Influence of curved thin-film device on deformation of a solar sail

A spinning solar sail IKAROS’s membrane is estimated to unexpectedly deform into an inverted pyramid shape due to thin-film devices with curvature, such as thin-film solar cells and steering devices on the membrane. It is important to investigate the deformation caused by the curved thin-film devices and predict the sail shape because the out-of-plane deformation greatly affects solar radiation pressure (SRP) and SRP torque. The purpose of this paper is to clarify the relationship between the global shape and orientation and position of curved thin-film devices and to evaluate SRP torque on the global shape using finite element analysis. The global shape is evaluated based on the out-of-plane displacement and the SRP torque. When the curved thin-film devices make the membrane shrink in the circumferential, diagonal, and radial direction, the sail deforms into a pyramid shape, an inverted pyramid one, and a saddle one, respectively. The saddle shape is more desirable for solar sails than the inverted pyramid shape and the pyramid one from the viewpoint of shape stability to SRP and control of SRP torque in the normal direction of the sail (windmill torque). The position of the thin-film device tends to increase the absolute value of windmill torque when it is biased circumferentially from the petal central axis. The suggested design principles for the arrangement of thin-film devices is that the curved thin-film devices should be directed so that the sail shrinks in the radial direction in order to deform the sail into a saddle shape with high shape stability, and the position of the thin-film devices should be biased in the circumferential direction paying attention to the absolute value of windmill torque to determine the direction of windmill torque.     

Deorbiting spacecraft with passively stabilised attitude using a simplified quasi-rhombic-pyramid sail

This paper studies deorbiting using an analogue to the quasi-rhombic-pyramid concept for planar motion. The focus is on maintaining a stable (meaning oscillatory) attitude close to the direction of the velocity of the spacecraft relative to the atmosphere. The study consists of a massive computation of deorbit times chosen in a region of the phase space where atmospheric drag plays a leading role. Here, no damping effects are considered. Thus, any passive stabilisation observed is either due to solar radiation pressure or atmospheric drag. The results show that such stable deorbiting is feasible up to a threshold that depends upon the physical parameters of the sail. This threshold is around 500 km of altitude. Stable deorbiting is also shown to reduce the unpredictability that appears due to tumbling.     

Drought prediction using the Along Track Scanning Radiometer (ATSR2) on board ERS2 satellite

Frequent monitoring and estimation of the areas under drought danger is important for agriculture, hydrology, weather, natural hazards and crop yield prediction.     

一种基于先验知识的3D位姿参数识别方法

计算机视觉中用单幅照片来识别三维物体的六个自由度是非常困难的，但是，在知道一些先验知识的情况下，可以对物体的六个自由度进行识别。本文提出一种基于先验知识的三维位举参数识别的方法，使用物体上不共线的三个特征点及目标点来确定物体的位置和姿态，给出了六个参数的解析表达式，在实时处理中可以得到好的效果。     

Charge exchange interactions on near-Earth proton radiation for orbit perturbation of high area-to-mass ratio objects

This novel concept expels neutral gas in the presence of geomagnetically-trapped protons in near-Earth orbit. The expelled neutral gas acts to induce charge exchange collisions with the geomagnetically-trapped protons and induce drag on objects which pass through it. The charge exchange collisions between the neutral gas and the geomagnetically-trapped protons create neutrals with similar kinetic energy that are not confined by the geomagnetic field. The charge exchange neutrals are able to collide with orbital objects and perturb their orbits. The delta-v applied by the charge exchange neutral flux is greatest on high area-to-mass objects. Numerical simulation shows charge exchange neutral impacts produce a delta-v on objects on the order of 3.8 x 10⁻¹¹ m/s at a distance of 1 km from the center of the expelled gas in a 1,000 km orbit. The impulse imparted by charge exchange neutral impacts is at least six orders of magnitude smaller than that provided by the induced drag caused by gas expulsion. The localized drag increase can force a majority of small objects into the orbit of the expelled gas cloud, even if that orbit is retrograde to the initial orbit of the objects. This new technique can be applied to the remediation of space debris.     

An overview of RADOM results for earth and moon radiation environment on Chandrayaan-1 satellite

The RADiatiOn Monitor (RADOM) is a miniature dosimeter-spectrometer that flew onboard the Chandrayaan-1 lunar mission in order to monitor the local radiation environment. Primary objective of the RADOM experiment was to measure the total absorbed dose, flux of surrounding energetic particles and spectrum of the deposited energy from high energy particles both en-route and in lunar orbit. RADOM was the first experiment to be switched on after the launch of Chandrayaan-1 and was operational until the end of the mission. This paper summarizes the observations carried out by RADOM during the entire life time (22 October 2008–31 August 2009) of the Chandrayaan-1 mission and compares the measurement by RADOM with the radiation belt models such as AP-8, AE-8 and CRRESS.     

Reanalysis of radiation belt electron phase space density using various boundary conditions and loss models

Data assimilation is becoming an increasingly important tool for understanding the near Earth hazardous radiation environments. Reanalysis of the radiation belts can be used to identify the electron acceleration mechanism and distinguish local acceleration from radial diffusion. However, for any practical applications we need to determine how reliable is reanalysis, and how significant is the dependence of the results on the assumptions of the code and choice of boundary conditions. We present the sensitivity of reanalysis of the radiation belt electron phase space density (PSD) to the assumed location of the outer boundary, using the VERB code and a Kalman filter. We analyze the sensitivity of reanalysis to changes in the electron-loss throughout the domain, and the sensitivity to the assumed boundary condition and its effect on the innovation vector. All the simulations presented in this study for all assumed loss models and boundary conditions, show that peaks in the phase space density of relativistic electrons build up between 4.5 and 6 R_E during relativistic electron flux enhancements in the outer radiation belt. This clearly shows that peaks build up in the heart of the electron radiation belt independent of the assumptions in the model, and that local acceleration is operating there. The work here is also an important step toward performing reanalysis using observations from current and future missions.