Research on internal gravity waves in the Martian atmosphere based on Tianwen-1 and Mars Global Surveyor occultation data

Internal gravity waves(IGWs)are critical in driving Martian atmospheric motion and phenomena.This study investigates Martian IGWs by using high-resolution data from China’s Tianwen-1 mission and the National Aeronautics and Space Administration’s Mars Global Surveyor(MGS)by the radio occultation(RO)technique.Key IGW parameters,such as vertical and horizontal wavelengths,intrinsic frequency,and energy density,are extracted based on vertical temperature profiles from the Martian surface to~50 km altitude.Data reveal that the Martian IGWs are predominantly small-scale waves,with vertical wavelengths between 6 and 13 km and horizontal wavelengths extending to thousands of kilometers.These waves propagate almost vertically and exhibit low intrinsic frequencies close to the inertial frequency,with the characteristic of low-frequency inertial IGWs.Tianwen-1 data indicate stronger IGW activity,higher energy density,and less dissipation than MGS data in the northern hemisphere.Moreover,MGS data in the southern hemisphere show higher buoyancy frequencies and lower vertical wavelengths,suggesting more stable atmospheric conditions conducive to IGW propagation.These extracted IGW characteristics can enhance our understanding of the atmospheric dynamics on Mars and contribute valuable information for parameterization in global circulation models.

The Mars orbiter magnetometer of Tianwen-1:in-flight performance and first science results

The Mars Orbiter MAGnetometer(MOMAG)is a scientific instrument onboard the orbiter of China’s first mission for Mars—Tianwen-1.Since November 13,2021,it has been recording magnetic field data from the solar wind to the magnetic pile-up region surrounding Mars.Here we present its in-flight performance and first science results,based on its first one and one-half months’data.Comparing these early MOMAG observations to the magnetic field data in the solar wind from NASA’s Mars Atmosphere and Volatile EvolutioN(MAVEN)mission,we report that the MOMAG magnetic field data are at the same level in magnitude,and describe the same magnetic structures with similar variations in three components.We recognize 158 clear bow shock(BS)crossings in these MOMAG data;their locations match well statistically with the modeled average BS.We also identify and compare five pairs of datasets collected when Tianwen-1’s orbiter and the MAVEN probe made simultaneous BS crossings.These BS crossings confirm the global shape of modeled BS,as well as the south-north asymmetry of the Martian BS.Two cases presented in this paper suggest that the BS is probably more dynamic at flank than near the nose.So far,MOMAG performs well,and provides accurate magnetic field vectors.MOMAG is continuously scanning the magnetic field surrounding Mars.Data from MOMAG’s measurements complement data from MAVEN and will undoubt edly advance our understanding of the plasma environment of Mars.

Proton pitch angle distributions in the Martian induced magnetosphere: A survey of Tianwen-1 Mars Ion and Neutral Particle Analyzer observations

The pitch angle distributions of ions and electrons can be affected by various processes;thus,they can serve as an important indicator of the physical mechanisms driving the dynamics of space plasmas.From observations from the Mars Ion and Neutral Particle Analyzer onboard the Tianwen-1 orbiter,we calculated the pitch angle distributions of protons in the Martian induced magnetosphere by using information from the magnetohydrodynamically simulated magnetic field,and we statistically analyzed the spatial occurrence pattern of different types of pitch angle distributions.Even though no symmetrical features were seen in the dataset,we found the dominance of the field-aligned distribution type over the energy range from 188 to 6232 eV.Maps of the occurrence rate showed the preferential presence of a trapped-like distribution at the lower altitudes of the surveyed nightside region.Although our results are more or less restricted by the adopted magnetic field,they indicate the complexity of the near-Mars proton pitch angle distributions and infer the possibility of wave–particle interactions in the Martian induced magnetosphere.

Observations and interpretations of geomorphologic features in the Tianwen-1 landing area on Mars by using orbital imagery data

China’s first Mars exploration mission,Tianwen-1,successfully landed in southern Utopia Planitia on Mars on May 15,2021.This work presents a detailed investigation of the geologic context of the landing area surface for this mission based on orbital remotesensing data.We constructed a geomorphologic map for the Tianwen-1 landing area.Results of our detailed geomorphologic map show several major landforms within the landing area,including rampart craters,mesas,troughs,cones,and ridges.Analysis of materials on the landing area surface indicates that most of the landing area is covered by Martian dust.Transverse aeolian ridges are widely distributed within the landing area,indicating the surface contexts were(and still are)modified by regional winds.In addition,a crater counting analysis indicates the landing area has an absolute model age of~3.3 Ga and that a later resurfacing event occurred at~1.6 Ga.Finally,we outline four formational scenarios to test the formation mechanisms for the geomorphologic features on the landing area surface.The most likely interpretation to explain the existence of the observed surface features can be summarized as follows:A thermal influence may have played an important role in the formation of the surface geomorphologic features;thus,igneous-related processes may have occurred in the landing area.Water ice may also have been involved in the construction of the primordial surface configuration.Subsequent resurfacing events and aeolian processes buried and modified the primordial surface.

Ground calibration of the Mars orbiter magnetometer onboard Tianwen-1

Ground calibration experiments of the Mars orbiter magnetometer(MOMAG)onboard the orbiter of Tianwen-1 were performed to determine the sensitivity,misalignment angle,and offset of the sensors.The linearity of the applied calibrated magnetic fields and the output from the sensors were confirmed to be better than 10^(-4),and the sensor axes were orthogonal to each other within 0.5 degrees.The temperature dependencies of the sensitivity and misalignment angle were examined,but no clear signatures of temperature dependencies could be seen.Sensor offset and the stability of sensor offset drift with a temperature change were also determined by the rotation method.The stability of the sensor offset drift was less than 0.01 nT/℃.The ground calibration of MOMAG determines all the calibration parameters of the sensors for accurate magnetic field measurements in orbit with the appropriate corrections.

Mars Orbiter magnetometer of China’s First Mars Mission Tianwen-1

As one of the seven scientific payloads on board the Tianwen-1 orbiter,the Mars Orbiter Magnetometer(MOMAG)will measure the magnetic fields of and surrounding Mars to study its space environment and the interaction with the solar wind.The instrument consists of two identical triaxial fluxgate magnetometer sensors,mounted on a 3.19 meter-long boom with a seperation of about 90 cm.The dual-magnetometers configuration will help eliminate the magnetic field interference generated by the spacecraft platform and payloads.The sensors are controlled by an electric box mounted inside the orbiter.Each magnetometer measures the ambient vector magnetic field over a wide dynamic range(to 10,000 nT per axis)with a resolution of 1.19 pT.Both magnetometers sample the ambient magnetic field at an intrinsic frequency of 128 Hz,but will operate in a model with alternating frequency between 1 and 32 Hz to meet telemetry allocations.

The payloads of planetary physics research onboard China’s First Mars Mission (Tianwen-1)

Mars is not only our nearby but also the most Earth-like planetary neighbor.Scientific exploration of Mars is thus of crucial value to our understanding of the solar system.The existence of abundant evidence for the former presence of water on Mars demands further exploration for signs of life on our sister planet,and investigations that could shed light on conditions favorable to the origin of life.For nearly 60 years,humans have conducted orbitally-based remote sensing and in-situ surface exploration of Mars,leading to many significant scientific discoveries.But much remains to be done before we can be sure that we truly and fully understand Mars.Key research topics include the history of water on Mars and how that history relates to the planet’s habitable environment-past,present,and future;the distribution and evolution of waterbearing and evaporative salt minerals on the planet’s surface;the history of volcanic activity on Mars;the Martian magnetic field and its effect on the escape of water and atmosphere from the planet;interactions between the solar wind and the Martian atmosphere and ionosphere;atmospheric characteristics and climate change on Mars;and so on(Li CL et al.,2018;Liu JJ et al.,2018).Based on the above scientific questions about life,climate,and geology on Mars,the international planetary science community has formulated ambitious Mars exploration programs.

Overview of the Mars climate station for Tianwen-1 mission

The background and scientific objectives of the Mars Climate Station(MCS)for Tianwen-1 are introduced,accompanied by a comparative review of the status of related meteorological observation missions and of advanced sensing technologies.As one of the China Tianwen-1 Mission’s principal scientific payloads,the MCS contains four measurement sensors and one electronic processing unit that are specially designed to measure local temperature,pressure,wind,and sound on the Martian surface.The MCS’s measurement principles,technical schemes,ground calibration techniques,and adaptability evaluation to the Mars surface environment of MCS are introduced in details.The conclusion presents measurement performance specifications of the MCS,based on ground test results,that will provide guidance to future research based on data from the Tianwen-1 and later Mars missions.

Calibration of Mars Energetic Particle Analyzer (MEPA)

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.

YH-1火星探测器设计及研制进展

介绍了中国首颗YH-1火星探测器的任务功能、组成和主要技术指标。给出了探测器设计中的火星探测超低温适应、深空探测自主姿态确定与控制、超远距离通信、休眠唤醒和剩磁控制等关键技术,以及相应的解决途径。试验和验证结果表明:YH-1火星探测器的设计满足火星探测特殊环境的任务要求。其设计和试验技术可直接用于我国其他深空探测项目,为后续深空探测积累了经验。

YH-1火星探测器射频波导测试技术

研究了一种在普通厂房内对萤火一号(YH-1)火星探测器进行射频测试的天线波导射频技术。给出了发射和接收天线波导设计,以及天线波导测试的方法、步骤和测试结果。对电场辐射强度分析表明:采用该天线波导转换器可在普通厂房内进行射频无线测试,满足深空航天器射频测试要求,提高了测试的完整性和安全性。

The solar wind plasma upstream of Mars observed by Tianwen-1:Comparison with Mars Express and MAVEN

On the great journey to Mars,China’s first planetary exploration mission,the Tianwen-1 came within 26 million kilometers of Mars from 31 October 2020 to 25 January 2021 and was getting closer to its destination,the red planet,in search of answers to the cataclysmic climate change that occurred in Martian history.Both the escape of the Martian atmosphere and the loss of surface water were firmly influenced by solar activities.Tianwen-1 provided a unique chance to depict the solar wind streams between Earth and Mars during the minimum of Solar Cycle 25.During the three-month cruise phase of Tianwen-1,the solar wind flows were successively observed at Earth,Tianwen-1,and Mars.After the field of view correction and noise reduction,the solar wind velocity and density measured by Tianwen-1 show good agreement with those at Earth and Mars.The results indicate that the performance of the ion analyzer onboard the Tianwen-1 orbiter is reliable and stable.It is worth looking forward to the joint observations of ion escape with other Mars probes in the following Martian years.

End-to-end Mars entry,descent,and landing modeling and simulations for Tianwen-1 guidance,navigation,and control system

On May 15,2021,the Tianwen-1 lander successfully touched down on the surface of Mars.To ensure the success of the landing mission,an end-to-end Mars entry,descent,and landing(EDL)simulator is developed to assess the guidance,navigation,and control(GNC)system performance,and determine the critical operation and lander parameters.The high-fidelity models of the Mars atmosphere,parachute,and lander system that are incorporated into the simulator are described.Using the developed simulator,simulations of the Tianwen-1 lander EDL are performed.The results indicate that the simulator is valid,and the GNC system of the Tianwen-1 lander exhibits excellent performance.

火星探测器动力学模型优化及“天问一号”探测器定轨研究

对上海天文台火星探测器定轨软件的动力学模型进行优化和升级,开发形成了MarsODP V2.0,该软件可以处理多种类型测量数据。对火星进行高精度动力学建模,考虑火星本身特性,增加了火卫一和火卫二的三体摄动、火星大气阻力摄动以及多种火星定向模型优化等。利用MEX实测数据比较了优化前后的火星定轨软件的定轨精度,计算结果表明,动力学模型优化后,定轨精度明显提升,与参考轨道的位置差异和速度差异减小;利用实测数据对美国MRO探测器进行精密定轨并验证软件优化后定轨精度。对“天问一号”探测器环火轨道进行定轨计算分析。

面向火星探测的环氧形状记忆聚合物复合材料的性能研究

国家火星探测任务是建设航天强国进程中的重大标志性工程,是中国航天走向更远深空的里程碑工程.智能材料这种集材料、结构和功能于一体的先进材料将会对火星探测任务有所助力.形状记忆聚合物及其复合材料作为一种典型的智能材料,可在有效减轻载荷的同时实现自主变形,已经在地球同步轨道航天器的应用中崭露头角.因此有必要研究这种新型环氧基形状记忆聚合物复合材料应用于火星探测工程的可能性.首先,针对“天问一号”火星探测器的任务需求,设计了一个具有自释放功能的着陆平台国旗装置.其中的锁紧释放装置由碳纤维增强的形状记忆聚合物复合材料制成,分别从静态拉伸力学性能、动态热机械性能和形状记忆性能三个角度评估了空间辐照和长期存储对形状记忆聚合物复合材料的影响.其中,空间辐照包括γ射线和紫外射线,辐照剂量分别为5×10^(5)rad和23.6 kCal.长期存储分为低温-196℃、室温25℃和高温85℃存储30天,和低温-196℃存储457天两组实验.最后,从“祝融号”火星车所携带相机拍摄的照片可以看到五星红旗被成功释放,旗面平整、图案清晰.这说明所研究的环氧基形状记忆聚合物复合材料可成功应用于火星探测任务,未来有望以多种结构形式助力我国的火星采样返回乃至其它深空探测任务.

“天问一号”火星探测器着陆控制方案研究

本文先依据“天问一号”着陆的有关数据,运用数学和物理方法,建立着陆器的运动模型方程;再借助蒙特卡罗模型和遗传算法,分别基于耗时最短、燃耗最优的目标,设计着陆的控制策略。根据“天问一号”着陆的真实值数据,对模型进行了匹配度检验,结果表明:运动模型结果与真实值数据的误差较小,说明该运动模型具有可靠性,可以使其广泛应用于人类对其他星球的进一步探测,为宇宙探测计划提供参考性技术。

Evolution History of Mesas in the Southern Utopia Planitia and Implications for the Ancient Oceans on Mars

As one of the prominent landforms in the Zhurong landing region,mesas are geological features with flat tops and steep marginal cliffs.The mesas are widely distributed along the dichotomy boundary.There are various interpreted origins proposed for the mesas,such as the erosion of sedimentary layers,tuyas eruptions,or surface collapse due to the catastrophic release of groundwater.We investigate the detailed morphological characteristics of the mesas on the Late Hesperian Lowland unit within the Utopia Planitia.We observe morphological evidence for both the ice-bearing interior mesas and the sedimentary origin,including(1)small pits on the crater wall and mesa cliff formed by the release of volatiles like ice;(2)lobate flows at the base of mesas formed by the melting of subsurface ice;(3)layered mesas indicating sedimentary origin;(4)grooves on the top surface of mesas formed by the volumetric compaction of sedimentary deposits.The results indicate that the mesas in the study area are formed by the erosion of sedimentary layers and representative of the Noachian oceanic sediments.We propose an evolutionary model for the mesas.This study will provide some insights into future research of ancient ocean hypothesis of Mars and interesting targets for the exploration of the Zhurong rover.

The Development of Emergency Communication Device for Tianwen-1 Probe

Mars is one of the most valuable planets for space exploration.After entering the entry descent and landing(EDL)phase,the spacecraft would carry out a series of procedural deceleration operations and achieve soft landing on the surface of Mars.In the process of EDL,the landing platform would encounter a series of irreversible incidents within environmental unpredictability,making this process highly risky.The emergency communication device plays an important role if in the Mars Exploration Program.It can capture and store key dynamic parameters during EDL phase,enabling a high probability of survival in the occurrence of a faulty condition.It can also send the stored data to the Mars obit probe when the communication condition is met.This paper presents a scheme design for the emergency communication device based on its functionality and performance requirements.It includes the design proposal,simulation results,reliability analysis,technical risks and control measures,inheritance and performance compliance which verifies the rationality and correctness of the design.

天问一号着陆巡视器进入舱GNC系统设计与实现

为了应对火星EDL过程的短时间、大测控时延、大冲击力学环境以及无高精度地图的特点,进入舱GNC系统开展了一系列高自主、强容错设计。全系统热备份、关键功能异构热备份的设计确保了对产品故障的自主诊断与快速处理;系统工作模式自主转换、关键模式转换多判据备份的策略提高了系统的容错能力;产品供电的自主抗冲击管理、触地开关的自主故障诊断与处理策略,确保了对火工品起爆等大冲击高动态工况的有效应对;针对背罩-组合体规避及地形障碍规避的需求,设计了一套激光产品和光学产品有机融合的避障系统及使用策略。设计了直升机挂飞等专项试验对系统设计进行验证。天问一号进入舱GNC系统在轨顺利实施了展配平翼等关键动作,完成了背罩以及地形障碍的规避,实现了3.1 km的最终着陆精度,充分证明了系统设计的正确性。

天问一号火星探测器产品保证工作实践

分析了火星探测器任务环境复杂、软件自主性高、验证任务重、材料选用控制难等特点,总结了天问一号火星探测器在狠抓风险识别与管控、聚焦软件系统设计源头,严格试验考核,以及严控材料选用及验证等方面采取的主要产品保证工作措施。上述措施有效保证了天问一号火星探测器的产品质量,可为后续火星探测器及其他行星际探测器研制过程的产品保证工作提供借鉴。