Abstract On 2022‐02‐15, solar eruptions caused one of the most intensive Solar Particle Events (SPEs) in Solar Cycle 25 observed at various heliospheric locations. This study focuses on the enhancements of energetic proton flux observed by multiple detectors located at the orbit and on the surface of Mars. We carry out the first analysis by the Mars Energetic Particle Analyzer (MEPA) instrument on board the Chinese Tianwen‐1 spacecraft (TW‐1) at Mars orbit which also serves to validate the instrument's capability to measure protons of up to 100 MeV. We reconstruct the event spectrum up to 1 GeV and further model the event doses at Mars's orbit and surface which are then validated against the corresponding dosimetry data. Our study utilizes all available radiation detectors at Mars, advances our understanding of Mars's radiation environment induced by large SPEs, and emphasizes the necessity of continuous and synergistic radiation monitoring at Mars.

In this work, a matchbox-sized dust detector with a wide measurement range was developed for the lunar surface applications. The characteristics of the detector response to lunar dust simulant deposition mass, particle size, light incidence angle, and temperature are investigated experimentally. It is found that in current study the shortcircuit current of the dust detector decreases with the increase in dust deposition mass overall. However, the pattern of current reduction is closely dependent on the size of the dust particles. Specifically, for the dust particle in the range of 75-100 mu m, the short-circuit current of the detector tends to decrease slowly and approximately linearly as the dust deposition mass increases, irrespective of light incidence angle. However, for the particle in the size range of 0-25 mu m, the decrease of short-circuit current with dust deposition mass can be well described by an exponential function. In addition, the occlusion coefficients for different particle size distributions at different light incidence angles, ranging from -0.88 to -0.08, are also obtained, which is important for determining the mass range of dust deposited on lunar surface-mounted detector at the corresponding conditions. The present research can provide guidance for lunar dust detection with solar cell-based detector.

During landing, the plume from the lander erodes the regolith on the lunar surface, thus destroying the nature of this surface. Landing also provides an opportunity to extract the mechanical properties of the lunar regolith in situ and to study wind erosion on airless bodies such as the Moon. Our goal in this study is to quantify the interparticle force of the lunar regolith, the erosion depth, and other parameters and to test the reliability of the plume erosion model. The erosion depth provides the necessary reference information for the precise interpretation of scientific results obtained from returned samples. We measure the total mass of the lunar regolith mobilized by the plume during the Moon landing. This information is also helpful for future lunar missions. With high-quality data from the Chang’E-5 (CE-5) and Chang’E-4 (CE-4) missions, we measure the erosion depth and the total mass and combine the results with computational fluid dynamics (CFD) to extract the interparticle force. We then test the plume erosion model according to the results from image measurement and CFD and propose a new formula with which to calculate the threshold friction velocity at which plume erosion is initiated. This calculation shows that the interparticle force for a 4-μm-diameter particle is 3.38–16.1 nN. The results also show that the CE-5 landing plume stripped away a 1.2-cm-deep layer of regolith, creating a ≈10-m-diameter crater on the lunar surface, and dispersed ≈441 kg of lunar regolith. Any analysis of a CE-5 drilling sample that is sensitive to the regolith depth must consider this 1.2-cm-thick eroded layer. When a plume erodes the lunar surface, the minimum shear stress required is much less than that predicted by the erosion model, which can no longer be used to predict whether erosion will occur.

In this study, a numerical model of quartz crystal microbalance (QCM) of a space atmospheric density sensor is developed. To reduce the heating time of desorption, the two-section linear and nonlinear radiation surfaces are proposed to optimize the heat transfer characteristics of the heating shell based on the self-directed online machine learning optimization (SOLO) approach. SOLO approach integrates deep neural network (DNN) with the finite elements method (FEM), which substitutes the objective as a function of design variables. New training data is generated dynamically based on the DNN's prediction of the shortest heating time of QCM space atmospheric density sensor. For the optimal two-section radiation surface, H1, L1 (height and horizontal span of first section radiation surface) are selected as the variables to be optimized. The optimal design values are 4.32 mm and 2.53 mm, respectively, the corresponding heating time is about 99.8 s, which approximately reduces 15% compared with the original structure. For the nonlinear radiation surface, the generatrix of the first section follows an exponential function a(ebx-1), the second section follows a logarithmic function cln(dx + 1), the distance between the top of heating shell and the boundary point of the two section is denoted as Hn. a, b, c, d and Hn are selected as the variables to be optimized, the optimal design values are 1.84, 0.79, 1.72, 45.99 and 0.5 mm, respectively, the corresponding heating time is about 97.7 s, which approximately reduces 18.6% compared with the original structure.

Engine plumes can seriously erode the Martian surface during the landing phase, causing a substantial alteration of the terrain of the immediate touchdown area and beyond. Furthermore, large amounts of lifted dust can block the view of boulders or craters, posing a serious threat to the lander's safety. Improving our understanding of the plume-surface interaction can reduce the risk of failure on a Mars landing mission. In situ studies on this subject are limited, particularly those relating to high-thrust single-nozzle engines. The Tianwen-1 represents the only Mars landing mission that employed such an engine with a thrust of -3000 N during the landing phase: Its success represents a unique opportunity in addressing this issue, providing an important reference for future Mars return missions. Here, we report the evolution characteristics of the plume-induced regolith erosion and the plume impingement effect measurements at the Tianwen-1 landing site. The results show that depressions and infilling are a complex process accompanying the changing of patterns as the lander descends. Specifically, the plume will seriously erode the area beneath the nozzle, causing the formation of a deep crater. Meanwhile, the expanding radial flow tends to flatten the peripheral area of the lander, which depends on the homogeneity of the regolith. To better quantify the impingement effects, some crucial parameters were extracted. The measured volume, diameter, and depth of the crater are 0.115 +/- 0.019 m3, 1.50 m, and -0.35 m, respectively. We also calculated the total erosion area and volume as 4879.4 +/- 297.7 m2 and 376.9 +/- 102.2 m3. In addition, plumeinduced infilling/erosion depths and rates during the landing phase were measured. Further, we investigated the shallow stratigraphic architecture exposed by the plume-induced crater beneath the lander, showing that it represents probably dust/sand-coated black rocks above at least -35 cm thick, bright reddish materials. These results provide valuable insights into the plume impingement effects on the Martian surface and the shallow subsurface layer at the Tianwen-1 landing site, which will benefit future Mars explorations.

In recent years, the Lunar south pole region (SPR) has become the focus of future explorations due to its special illumination condition and the possible water ice in permanently shadowed craters around it. The Shackleton crater locates almost exactly at the Moon’s south pole and has become the hottest destination for several landing missions, including the Chang’E-7 mission. However, people still know little about the electric potential and the dust environment around this crater. In this paper, we develop an analytical model to study the surface potential and the electrostatic dust transport around the crater. It is found that the crater’s floor can be negatively charged due to the topographic shielding, and the surface potential is as low as −175 V on the leeward crater wall. Accordingly, a large number of charged dust grains can be emitted from the leeward crater wall, with a maximum height of about 10 km and a horizontal distance of about 40 km, which brings a local dust cloud around the crater. Both the topographic shielding and the local dust cloud are qualitatively verified by a numerical simulation, in which a typical dust density of 10 4 −10 5 m −3 is found near the crater. Our results are important to the environmental assessment for future explorations near the crater. Furthermore, the results are helpful to understand the surface charging and the electrostatic dust transport on the other airless bodies.

The plume-surface interaction that occurs as a result of a variable-thrust engine exhaust plume impinging on soil during landings is critical for future lunar mission design. Unique lunar environmental properties, such as low gravity, high vacuum, and the regolith layer, make this study complex and challenging. In this paper, we build a reliable simulation model, with constraints based on landing photos, to characterize the erosion properties induced by a low-thrust engine plume. We focus on the low-thrust plume-surface erosion process and erosion properties during the Chang’E-5 mission, aiming to determine the erosion difference between high- and low-thrust conditions; this is a major concern, as the erosion process for a low-thrust lunar mission is rarely studied. First, to identify the entire erosion process and its relative effect on the flat lunar surface, a one-to-one rocket nozzle simulation model is built; ground experimental results are utilized to verify the simulated inlet parameters of the vacuum plume flow field. Following that, plume flow is considered using the finite volume method, and the Roberts erosion model, based on excess shear stress, is adopted to describe plume-surface interaction properties. Finally, a Lagrangian framework using the discrete phase model is selected to investigate the dynamic properties of lunar dust particles. Results show that erosion depth, total ejected mass, and the maximum particle incline angle during the Chang’E-5 landing period are approximately 0.2 cm, 335.95 kg, and 4.16°, respectively. These results are not only useful for the Chang’E-5 lunar sample analysis, but also for future lunar mission design.

There are a lot of application requirements for liquid level measurement in engineering. At present, the formula of regular or uniform field is used in the calculation of the corresponding relationship between capacitance and liquid level of the capacitance liquid level sensor, which ignores the influence of the dispersion field on the capacitance distribution. There are some problems, such as unclear effective area of liquid level measurement and low accuracy of liquid level measurement. In order to further improve the accuracy of the sensor, the finite element method is used to simulate the electric field distribution of the capacitance sensor, analyze the influence of the dispersion field on the capacitance measurement, and carry out theoretical calculation and experimental verification, finally determine the effective measurement area of the liquid level. In this paper, a liquid level sensor which can be used in both conductive and nonconductive liquids is designed, which can save cost and achieve high sensitivity. Taking the conductive liquid as an example, the methods and suggestions to further improve the measurement accuracy of capacitive liquid level sensor are put forward.

Based on the two traditional flow sensor design methods of constant temperature difference and constant power, a double-winding distributed thermal flow sensor is proposed. The sensor measures the gas mass flow by heating the double-winding with constant power and collecting the sensor temperature using double-winding at the same time. Based on the principle of fluid flow and heat transfer, the flow measurement principle is analyzed, the temperature field of the sensor is simulated by COMSOL software, and the sensor structure is optimized to provide a reliable basis for sensor design. In order to obtain the correction formula between the outside temperature and the measured value of the sensor, a simulation calculation is carried out for different outside temperatures. Finally, a double-winding flow sensor is designed according to the optimization results. The sensor was tested on a standard flow output device to verify the feasibility of the sensor for flow measurement. The outside temperature test is carried out to verify that the sensor has good temperature adaptability. The results shows that the simulation results are in good agreement with the experimental results. The error is less than ±10% in the middle range of the sensor.

Solar energetic particles (SEPs) associated with flares and/or coronal mass ejection (CME)-driven shocks can impose acute radiation hazards to space explorations. To measure energetic particles in near-Mars space, the Mars Energetic Particle Analyzer (MEPA) instrument onboard China's Tianwen-1 (TW-1) mission was designed. Here, we report the first MEPA measurements of the widespread SEP event occurring on 29 November 2020 when TW-1 was in transit to Mars. This event occurred when TW-1 and Earth were magnetically well connected, known as the Hohmann-Parker effect, thus offering a rare opportunity to understand the underlying particle acceleration and transport process. Measurements from TW-1 and near-Earth spacecraft show similar double-power-law spectra and a radial dependence of the SEP peak intensities. Moreover, the decay phases of the time-intensity profiles at different locations clearly show the reservoir effect. We conclude that the double-power-law spectrum is likely generated at the acceleration site, and that a small but finite cross-field diffusion is crucial to understand the formation of the SEP reservoir phenomenon. These results provide insight into particle acceleration and transport associated with CME-driven shocks, which may contribute to the improvement of relevant physical models.

The development process of space Langmuir probe needs to complete a large number of tests and calibration tests on the ground. Due to the long calibration period, complexity and high cost of plasma environment calibration, calibration tests are usually carried out after the instrument has been developed, in order to conduct preliminary tests on Langmuir probe during the instrument development process to verify the performance, as well as to save the cost of calibration tests and increase the reliability of the instrument, An advanced spatial Langmuir probe volt-ampere(I-V) load simulator was designed in this paper. Based on the positive and negative polarity of the external bias voltage, the I-V characteristic curve of the Langmuir probe was divided into positive and negative characteristic curves, which were realized by the combination of the output characteristic curves of NPN and PNP transistors, and the diode switching selectivity. The laboratory test results were consistent with the theoretical curve, verifying the validity and compliance of the design, which can play an important role in supporting the development of the space Langmuir probe and the calibration of the plasma environment.

A Main Belt Comet exploration mission has been proposed to perform rendezvous with a Main Belt Comet in the future, and the probe will orbit the comet and carry on complete investigation. The scientific objective of the Main Belt Comet Dust Analyzer (MBCDA) instrument, part of the scientific payload onboard the Main Belt Comet mission, is to explore the ejections, orbit activity and origin of the comet, as well as dust evolution in the coma and their influence on the probe. To this aim, MBCDA is composed of different modules: a Microbalance Sensor system, to measure the dust flux from different directions and perform a thermo-gravimetric analysis, a Dust Size Sensor, to monitor the grain's diameter by optical detection, a Dust Momentum Sensor, to detect the momentum carried by the particles, and a Microscopic Imaging System, to obtain the morphological, charging properties and composition information of the comet dust. The preliminary calibration results of MBCDA demonstrate that the instrument is basically compatible with design specifications and is suitable to obtain scientific results about cometary dust.

The Mars radiation environment, both in past and at present, plays a vital role in the evolution of Martian atmosphere, so it is necessary to detect the background radiation environment both in the Martian atmosphere and the transfer orbit from Earth to Mars. The Tianwen-1 Energetic Particle Analyzer (EPA) is designed to measure and analyze the energetic charged particles emitted to the Martian atmosphere. Mars-EPA consists of two parts: one is the Mars-EPA sensor head and the other is the Mars-EPA electronics system. This paper begins with an introduction of Mars-EPA structure and function of each part, followed by a simulation of how sensor head structure is designed. It then evaluates the performance of detection system using Geant4 software, to whether this sensor is capable of identifying the target particle and proposes a reasonable ground calibration procedure, which allows on overall detection performance to some degree. This Mars-EPA has demonstrated a potentially high capability and configurability which hopefully will shed light on future development of compact energetic detectors in deep space exploration.

When the lander approaches the lunar surface, the rocket exhaust will erode the surface and eject massive high-speed dust, which could damage the payloads on the lander or interfere with subsequent surface operations. This process also provides a unique opportunity to study the plume-dust interaction and the wind erosion on the surface of airless body such as the Moon. Previously, limited knowledge was obtained from Apollo landing images and a simplified erosion model is built to study the erosion process. With high-quality data acquired in the landing process of Chang'E-4 (CE-4) mission, for the first time, we aim to quantify the dust ejection angle and erosion depth for a low-thrust lander, test the effectiveness of the current erosion model, and provide reference information for future landing missions. We use image measurement methods to extract key parameters such as dust ejection angle and erosion depth from the landing image of CE-4. For comparison with the observation, we also employ an erosion model to estimate the erosion thickness. The dust appears at about 7 s before the lander touch the surface, with a height of 13 m above the surface. When the nozzle altitude was about 0.6 m, the dust ejection angle is measured to be above 7 degrees, while the dust ejection angle calculated by the particle trajectory method is less than 4.3 degrees for particle sizes smaller than 1 mm. For the first time, an average erosion depth of 0.7 cm is measured between 1.12 m and 2 m from the nozzle centerline for a low-thrust lander. The measurement corresponds to an erosion time duration from 1.1 s before landing to 0.4 s after landing. The measured erosion range using CE-4 data is much larger than the estimated erosion radius given by the previous erosion model. It indicates that the dust's angular distribution, local topography of the landing area, and other factors are important in improving the precision of the erosion model.

This paper describes the scientific objectives and payloads of Tianwen-1, China’s first exploration mission to Mars. An orbiter, carrying a lander and a rover, lifted-off in July 2020 for a journey to Mars where it should arrive in February 2021. A suite of 13 scientific payloads, for in-situ and remote sensing, autonomously commanded by integrated payload controllers and mounted on the orbiter and the rover will study the magnetosphere and ionosphere of Mars and the relation with the solar wind, the atmosphere, surface and subsurface of the planet, looking at the topography, composition and structure and in particular for subsurface ice. The mission will also investigate Mars climate history. It is expected that Tianwen-1 will contribute significantly to advance our scientific knowledge of Mars.

Accurate simulation and calculation of the deposition of outgassing molecule can shorten the cycle and reduce the cost of vacuum tests on satellites. It also provides a reference for contamination protection design by systems engineers. In this study, the molecular outgassing, transport and deposition processes were simulated by diffusion theory, the angle coefficient method, and the first-order desorption equation, respectively. The simulation results were consistent with the test data trends, but deviated from the test values. Given the effect of initial molecular outgassing rate, diffusion coefficient and residence time on the deposition mass, it was surmised that considering the molecular species and the weight mass rate would improve the calculation result. These considerations indeed improved the numerical simulations of high-vacuum contamination.

Charged dust widely exists on the surface of the moon, which is considered to be closely related with many natural phenomena. China's Chang'E-5 lunar mission plans to monitor the charged characteristics of electrostatically levitated dust on the lunar surface in an economical and effective way. The designed detector consists of two probes, the reference probe and the measuring probe. Each single probe consists of two grids and a sticky quartz crystal microbalance. The sensitivity coefficient of measuring probe is SM=(8.002 +/- 0.510)x10-9g/Hz.cm2, and that of reference probe is SR=(9.137 +/- 0.369)x10-9 g/Hz.cm2 under the test. By comparing the measurement results of two sets of probes, the mass proportion of dust with different charge/mass ratio of suspended lunar dust can be obtained. These results measured on the lunar surface would be helpful for analyzing the levitation mechanisms and motion characteristics of lunar dust. (c) 2021 Elsevier B.V. All rights reserved.

A space floating potential detector (FPD) is an instrument being developed to study the charging of spacecraft structures. It measures the floating potential that arises as the spacecraft interacts with the low Earth orbit (LEO) plasma as well as the Earth’s magnetic field. The FPD belongs to the active potential control system and consists of three functional modules. Leakage current-eliminating and zero-clearing techniques are used in the detector design to ensure the measurement of the floating potential over the long term within the range from −150 to 0 V and at a voltage resolution of less than 1 V. In order to investigate the performance of the FPD, a typical LEO space plasma environment is simulated in the laboratory. The calibrations of the FPD show that the output voltage is basically linear with the input bias voltage, and the maximum nonlinear error is less than 0.9%.

The first Mars exploration mission of China (Tianwen-1) is scheduled to be launched in 2020; a charged particle telescope, the Mars Energetic Particle Analyzer (MEPA), is carried as one of the payloads on the orbiter. The MEPA is designed to measure solar energetic particles (SEPs) and galactic cosmic rays (GCRs) in the near-Mars space and in the transfer orbit from Earth to Mars. Before the launch, the MEPA was calibrated in ground experiments with radioactive sources, electronic pulses, and accelerator beams. The calibration parameters, such as energy conversion constants, threshold values for the triggers, and particle identification criteria, were determined and have been stored for onboard use. The validity of the calibration parameters has been verified with radioactive sources and beams. The calibration results indicate that the MEPA can measure charged particles reliably, as designed, and that it can satisfy the requirements of the Tianwen-1 mission.

It was suspected that the horizon glow observed over the lunar terminator was caused by electrostatically levitated dust particles, but do high concentrations of dust particles really exist over the lunar terminator? This is an important question that cannot be answered even today. In fact, no in situ investigations about the lunar dust have been conducted on lunar surface since Apollo. Here we first report in situ investigations of lunar dust at Chang'E‐3 (CE‐3) landing site using solar cell probe (SCP). The results show that, different from Apollo's observation, the short‐circuit current of SCP did not decrease sharply during the first several lunations except the first lunation, indicating the recently developed minimalist qualitative model of sunrise‐driven dust transport might not be applicable at the geologically young CE‐3 landing site. In addition, within detector's detection limit, no abrupt changes in dust concentration were observed above the sharp sunlight/shadow boundaries on lunar surface.