Candidate Landing Sites Research Articles

Investigation of the Regolith Thickness and Boulder Density at the Four Candidate Landing Sites of the Emirates Lunar Mission Rashid-1 Rover

Investigation of the Regolith Thickness and Boulder Density at the Four Candidate Landing Sites of the Emirates Lunar Mission Rashid-1 Rover

Efficient adversarial attacks detection for deep reinforcement learning-based autonomous planetary landing GNC

Given the constraints of remote communication and the unpredictability of the environment, autonomous planetary landing mechanisms are expected to achieve the high criteria of autonomy and provide optimal trajectory in future space exploration missions. As the results, applying Deep Reinforcement Learning (DRL) techniques into autonomous landing has produced encouraging findings. Due to the black-box nature of deep learning algorithms, one of the main concerns regarding the robustness of DRL is its vulnerability to adversarial attacks. This constraint prevents the transfer of DRL-based autonomous landing schemes from simulation to real-world applications. In this article, we explore how the DRL-based autonomous landing will be impacted by adversarial attacks and how to protect the system effectively and efficiently. To achieve this, a Long Short Term Memory (LSTM) based adversarial attack detector is been proposed. The proposed method adopts the explainability measurement of the target DRL scheme and flag the detection of adversarial attacks when acting. The proposed method is built and tested on 3D digital terrain model of Candidate Landing Site for 2020 Mission in Jezero Crater to simulate the landing scenario on the Mars. The experimental results demonstrate the proposed methodology can effectively detect adversarial attacks when acting on DRL agent with a high confidence in detection accuracy.

Candidate Landing Sites for the Emirates Lunar Mission (ELM) Rashid-1 Rover

Candidate Landing Sites for the Emirates Lunar Mission (ELM) Rashid-1 Rover

Stratigraphic cross-sections, geologic history, and provenance of material at the candidate landing sites of the Artemis missions

From the scientific perspective, Artemis lunar missions focus on the south circumpolar region (SCR) mainly to investigate the existence and abundance of volatiles and to explore and sample ancient lunar deposits. The volatile distribution is primarily related to the cold traps in permanently shadowed regions, while the availability of ancient material is due to the proximity to the early lunar ∼2300 km diameter South Pole-Aitken (SPA) impact basin. One of the critical factors for future missions will be determining the geological structure and provenance (sources) of material at each candidate landing site, which can be predicted utilizing three-dimensional stratigraphic reconstructions of geological map units and crater ejecta deposits. This type of reconstruction permits a better understanding of candidate material that can be collected and analyzed at each site, and a ranking of landing sites can be formulated on this basis. Here, we present reconstructed geological cross-sections at Artemis landing sites using our recent SCR geological map and numerical modelling of crater ejecta thicknesses and their sequence.

The Generation of High-Resolution Mapping Products for the Lunar South Pole Using Photogrammetry and Photoclinometry

High-resolution and high-accuracy mapping products of the Lunar South Pole (LSP) will play a vital role in future lunar exploration missions. Existing lunar global mapping products cannot meet the needs of engineering tasks, such as landing site selection and rover trajectory planning, at the LSP. The Lunar Reconnaissance Orbiter (LRO)’s narrow-angle camera (NAC) can acquire submeter images and has returned a large amount of data covering the LSP. In this study, we combine stereo-photogrammetry and photoclinometry to generate high-resolution digital orthophoto maps (DOMs) and digital elevation models (DEMs) using LRO NAC images for a candidate landing site at the LSP. The special illumination and landscape characteristics of the LSP make the derivation of high-accuracy mapping products from orbiter images extremely difficult. We proposed an easy-to-implement shadow recognition and contrast stretching method based on the histograms of the LRO NAC images, which is beneficial for photogrammetric and photoclinometry processing. In order to automatically generate tie points, we designed an image matching method considering LRO NAC images’ features of long strips and large data volumes. The terrain and smoothness constraints were introduced into the cost function of photoclinometry adjustment, excluding pixels in shadow areas. We used 61 LRO NAC images to generate mapping products covering an area of 400 km2. The spatial resolution of the generated DOMs was 1 m/pixel, and the grid spacing of the derived DEMs was 1 m (close to the spatial resolution of the original images). The generated DOMs achieved a relative accuracy of better than 1 pixel. The geometric accuracy of the DEM derived from photoclinometry was consistent with the lunar orbiter laser altimeter (LOLA) DEM with a root mean square error of 0.97 m and an average error of 0.17 m.

Mini-RF S-band Radar Characterization of a Lunar South Pole–crossing Tycho Ray: Implications for Sampling Strategies

One of the youngest features on the Moon is Tycho, an 85 km diameter impact crater with a vast ray system that spans much of the lunar nearside. As such, it serves as an important stratigraphic marker for the Moon. One of Tycho’s longest rays crosses the South Pole, where it intersects several candidate landing sites for NASA’s Artemis III mission, which intends to return new lunar samples. Identification of ray-related effects are thus important to understand the provenance of collected material. To help contextualize sampling strategies, here we characterize the South Pole–crossing Tycho ray using monostatic S-band radar observations from the Lunar Reconnaissance Orbiter’s Miniature Radio Frequency instrument. We found that the ray is a ∼15 km wide radar-bright feature extending at least ∼1600 km from Tycho. Polarimetric analysis revealed that the measured radar backscatter is consistent with a terrain enhanced in centimeter-to-decimeter-scale scatterers. Moreover, we found that the abundance of these scatterers likely decreases with distance from the primary crater, suggesting there may be less Tycho-disturbed material, in particular, poleward of 85°S, where the candidate landing sites are located. Nevertheless, we identified craters along the ray and, importantly, within the Haworth candidate landing site that exhibit secondary crater characteristics, such as radar-bright, asymmetric ejecta deposits. We showed, based on solar illumination and topographic slopes, that the likely Tycho-related secondaries within Haworth are accessible by landed missions. Exploration of this site may thus directly sample Tycho-disturbed material, including a nearby permanently shadowed region, providing new insights into lunar surface processes.

Character and spatial distribution of mineralogy at the lunar south polar region

The lunar south polar region, encompassing part of the South Pole-Aitken (SPA) basin, stands out as one of the most intriguing areas for future lunar exploration endeavors. Using the Moon Mineralogy Mapper (M3) data, we conducted a comprehensive investigation into the characteristics and distribution of minerals within the lunar south polar region, spanning from 80°S to the south pole. The cartographic outputs from this study, capable of delineating the composition and abundance of various minerals, have enabled the partitioning of the lunar south polar region into two distinct zones. The region situated within the inner ring of the SPA basin is characterized by an elevated abundance of low-Ca pyroxene, whereas the Feldspathic Highlands (FH) in the lunar south polar region and the outer ring of the SPA basin predominantly comprise feldspathic materials, albeit with localized pyroxene-rich areas. The dominant mafic component across the lunar south polar region is low-Ca pyroxene, with no evidence of olivine-rich materials being detected. The mineralogy of some candidate landing sites was illustrated and the hematite-bearing materials were observed at the rim of Shackleton and de Gerlache. Furthermore, we also identified an abundance plagioclase on the western rim of Shackleton. These findings underscore the significance of the lunar south polar region, not only as a promising locale for in situ resource utilization (ISRU) in forthcoming lunar missions but also as a key site for advancing our understanding of the Moon's geological evolution.

Characterization of the Moon’s South polar craters using optical, microwave and thermal remote sensing

The peculiar illumination and insolation conditions at the poles of the Moon lead to the formation of Permanently Shadowed Regions (PSR) that act as cold traps for volatiles and are important for In Situ Resource Utilization (ISRU). However, since these regions lie in shadows of surrounding topographic highs, the ability of optical remote sensing in imaging these regions for photo reconnaissance is limited and using other modes of remote sensing becomes imperative. In this work, reflectance from optical data, backscatter from active microwave data and temperature from thermal data from the surfaces of three craters – de Gerlache, Haworth and Shoemaker – on the South Pole of the Moon, in close proximity to the Artemis III candidate landing sites, has been studied. Images from Clementine UVVIS, LRO WAC and LRO NAC have been compared with fully polarimetric data from the L-bands sensor of Chandrayaan-2 DFSAR. Further, the temperatures at the surface of the craters have been studied using data from LRO DIVINER. Since large parts of the craters under study lie in permanent shadows, Clementine UVVIS and LRO WAC could image only some parts of the rims. LRO NAC, with its longer exposure times, could image some parts within the crater however the walls of the crater and the floor near the walls remained in shadow. DFSAR was found to be useful in viewing the permanently shadowed regions of the craters. Overall, the backscatter in HH and VV (co-pol) channels was higher than the backscatter in HV and VH (cross-pol) channels. The elevated rims of the craters were clearly visible in co-pol channels and the rough texture of the ejecta of the craters had a distinct high backscatter in cross-pol channels. This fully polarimetric data can be used to map the interiors of the craters where optical data has low albedo. Analysis of the thermal data revealed that within the craters, in the regions that were in perpetual shadows, the maximum summer temperatures were less than 150 K making these regions cold traps for volatiles and possible locations of surface water–ice. The parts of craters lying in the shadows of surrounding higher features had lower maximum temperatures in summer and the parts facing them had higher maximum temperatures due to reflected insolation. Seleno Referenced Image (SRI) product from Chandrayaan-2 DFSAR was found to be a viable alternative to optical data for viewing the PSRs and for their geologic mapping.

Illumination and regolith temperature at China’s next candidate lunar landing site Shackleton crater

This study focuses on the illumination and temperature at China’s next lunar candidate landing site Shackleton crater. We used the NASA’s SPICE system to evaluate the terrain obscuration effect on real-time illumination; the resulting illumination map resembles previous studies, validating the methodologies used in our study. In addition, we estimated an accumulated illumination map for the period of likely rover movement. The map indicates the illuminated inner wall of the Shackleton crater is close to 27% of the whole, meaning that the rover will likely receive solar radiation during its movement. Using the real-time illumination and the distributed 1-D thermal diffusion model, we continuously evaluated the regolith temperature for more than 20 years to stabilize the temperature, and selected the temperature of the end time as the initial value used in a thermal study set for July 20, 2023 and May 8, 2027. Our results indicate the temperature in the permanent shadow region remains nearly constant, thus validating the stability of our estimated initial temperature. Our results also indicate that the surface temperature is more sensitive to transient illumination, but the subsurface temperature is more likely to be associated with the accumulated illumination. This difference indirectly implies that the conductivity of the lunar regolith is inefficient. The locations receiving more solar radiation show a temperature larger than the threshold (∼112 K) of ice stability. The permanently shadowed regions can be as cold as 25 K, and such extreme coldness is a hazard to the rover. There are suitable temperature locations which have a warm surface but cold subsurface to preserve water ice. To further ensure normal rover movement, we provided a map of suitable temperature sites and found that these locations exist not only in the Shackleton crater’s inner wall, but also outside the crater. We suggested four trade-off sampling sites with suitable temperatures and gradual slopes.

ELCD: Efficient Lunar Crater Detection Based on Attention Mechanisms and Multiscale Feature Fusion Networks from Digital Elevation Models

The detection and counting of lunar impact craters are crucial for the selection of detector landing sites and the estimation of the age of the Moon. However, traditional crater detection methods are based on machine learning and image processing technologies. These are inefficient for situations with different distributions, overlaps, and crater sizes, and most of them mainly focus on the accuracy of detection and ignore the efficiency. In this paper, we propose an efficient lunar crater detection (ELCD) algorithm based on a novel crater edge segmentation network (AFNet) to detect lunar craters from digital elevation model (DEM) data. First, in AFNet, a lightweight attention mechanism module is introduced to enhance the feature extract capabilities of networks, and a new multiscale feature fusion module is designed by fusing different multi-level feature maps to reduce the information loss of the output map. Then, considering the imbalance in the classification and the distributions of the crater data, an efficient crater edge segmentation loss function (CESL) is designed to improve the network optimization performance. Lastly, the crater positions are obtained from the network output map by the crater edge extraction (CEA) algorithm. The experiment was conducted on the PyTorch platform using two lunar crater catalogs to evaluate the ELCD. The experimental results show that ELCD has a superior detection accuracy and inference speed compared with other state-of-the-art crater detection algorithms. As with most crater detection models that use DEM data, some small craters may be considered to be noise that cannot be detected. The proposed algorithm can be used to improve the accuracy and speed of deep space probes in detecting candidate landing sites, and the discovery of new craters can increase the size of the original data set.

A multi-lander New Frontiers mission concept study for Enceladus: SILENUS

Enceladus, with its subsurface ocean, is amongst the top priority targets in the search for life beyond Earth. Following on discoveries from the Cassini mission that Enceladus possesses a global subsurface ocean containing salt and organic compounds, there are many unconstrained properties of the ocean and ice shell that must be investigated to further assess the habitability of Enceladus and begin the search for biosignatures on Enceladus. In this paper, we present a concept study for a New Frontiers class multi-lander and orbiter mission to Enceladus that investigates if there is or ever was a habitable environment on Enceladus. The mission architecture includes an orbiter for detailed chemical analysis of material erupted from Enceladus’ plumes and four impact landers for geophysical measurements. As part of our mission concept study, we explore key trades for orbital and surface science, as well as assess the scientific potential and hazards of candidate landing sites on Enceladus. The novelty of our mission architecture and consideration of both orbital and surface science elements makes this work directly relevant to a broad range of potential future mission architectures under consideration, such as those identified in the 2023–2032 Planetary Science and Astrobiology Decadal Survey.

Landing Site Detection for Autonomous Rotor Wing UAVs Using Visual and Structural Information

The technology of unmanned aerial vehicles (UAVs) has increasingly become part of many civil and research applications in recent years. UAVs offer high-quality aerial imaging and the ability to perform quick, flexible and in-depth data acquisition over an area of interest. While navigating in remote environments, UAVs need to be capable of autonomously landing on complex terrains for security, safety and delivery reasons. This is extremely challenging as the structure of these terrains is often unknown, and no prior knowledge can be leveraged. In this study, we present a vision-based autonomous landing system for rotor wing UAVs equipped with a stereo camera and an inertial measurement unit (IMU). The landing site detection algorithm introduces and evaluates several factors including terrain’s flatness, inclination and steepness. Considering these features we compute map metrics that are used to obtain a landing-score map, based on which we detect candidate landing sites. The 3D reconstruction of the scene is acquired by stereo processing and the pose of the UAV at any given time is estimated by fusing raw data from the inertial sensors with the pose obtained from stereo ORB-SLAM2. Real-world trials demonstrate successful landing in unknown and complex terrains such as suburban and forest areas.

Improving YOLOv5 with Attention Mechanism for Detecting Boulders from Planetary Images

It is of great significance to apply the object detection methods to automatically detect boulders from planetary images and analyze their distribution. This contributes to the selection of candidate landing sites and the understanding of the geological processes. This paper improves the state-of-the-art object detection method of YOLOv5 with attention mechanism and designs a pyramid based approach to detect boulders from planetary images. A new feature fusion layer has been designed to capture more shallow features of the small boulders. The attention modules implemented by combining the convolutional block attention module (CBAM) and efficient channel attention network (ECA-Net) are also added into YOLOv5 to highlight the information that contribute to boulder detection. Based on the Pascal Visual Object Classes 2007 (VOC2007) dataset which is widely used for object detection evaluations and the boulder dataset that we constructed from the images of Bennu asteroid, the evaluation results have shown that the improvements have increased the performance of YOLOv5 by 3.4% in precision. With the improved YOLOv5 detection method, the pyramid based approach extracts several layers of images with different resolutions from the large planetary images and detects boulders of different scales from different layers. We have also applied the proposed approach to detect the boulders on Bennu asteroid. The distribution of the boulders on Bennu asteroid has been analyzed and presented.

NOAH-H, a deep-learning, terrain classification system for Mars: Results for the ExoMars Rover candidate landing sites

In this investigation a deep learning terrain classification system, the “Novelty or Anomaly Hunter – HiRISE” (NOAH-H), was used to classify High Resolution Imaging Science Experiment (HiRISE) images of Oxia Planum and Mawrth Vallis. A set of ontological classes was developed that covered the variety of surface textures and aeolian bedforms present at both sites. Labelled type-examples of these classes were used to train a Deep Neural Network (DNN) to perform semantic segmentation in order to identify these classes in further HiRISE images.This contribution discusses the methods and results of the study from a geomorphologists perspective, providing a case study applying machine learning to a landscape classification task. Our aim is to highlight considerations about how to compile training datasets, select ontological classes, and understand what such systems can and cannot do. We highlight issues that arise when adapting a traditional planetary mapping workflow to the production of training data. We discuss both the pixel scale accuracy of the model, and how qualitative factors can influence the reliability and usability of the output.We conclude that “landscape level” reliability is critical for the use of the output raster by humans. The output can often be more useful than pixel scale accuracy statistics would suggest, however the product must be treated with caution, and not considered a final arbiter of geological origin. A good understanding of how and why the model classifies different landscape features is vital to interpreting it reliably. When used appropriately the classified raster provides a good indication of the prevalence and distribution of different terrain types, and informs our understanding of the study areas. We thus conclude that it is fit for purpose, and suitable for use in further work.

Planning for Landing Site Selection in the Aerial Supply Delivery

In the aerial supply delivery problem, an un-manned aircraft needs to deliver supplies as close as possible to the desired goal location. This involves choosing and landing at a landing site that is closest to or most accessible from the desired goal location. The problem is complicated by the fact that the status of candidate landing sites is unknown before the mission begins, and instead the aircraft needs to compute a sequence according to which it flies and senses the candidate landing sites in order to land as quickly as possible. The problem of computing this sequence corresponds to planning under uncertainty about environment. In this paper, we show how it can be solved efficiently via a recently developed probabilistic planning framework, called Probabilistic Planning with Clear Preferences (PPCP). We show that the problem satisfies the Clear Preferences assumption required by PPCP,and therefore all the theoretical guarantees continue to hold. The experimental results in simulation show that our approachcan solve large-scale problems in real-time while experiments on a physical quad-rotor provide proof of concept.

System analysis of a Moon base at the south pole: Considering landing sites, ECLSS and ISRU

The objective of this paper is to perform an in-depth feasibility analysis and dimensioning of a potential Environmental Control and Life Support System (ECLSS) and power system for a crewed lunar base at the lunar south pole. The analyzed ECLSS includes an In-Situ Resource Utilization (ISRU) reactor for oxygen resupply and a Regenerative Fuel Cell System (RFCS) as power supply during shadow phases. The co-dependencies and interactions between the ECLSS sub-systems themselves and with the environment are incorporated to achieve a holistic system analysis. We used a fixed ECLSS configuration based on the current NASA plans for a Moon base ECLSS with a fixed function-to-subsystem allocation. The performed trade-offs are then restricted within the design space, to e.g. resize tanks and individual subsystems instead of considering other possible subsystems. We chose this approach because the aim of this paper is to perform an in-depth system analysis of all related subsystems and their interaction with the environment instead of a top-level trade-off.The first step is the selection of a suitable landing site and the dynamic simulation of its lighting conditions over the investigated period of 1 year. We use a slope map with a resolution of 120 m per pixel, a Permanently Shaded Region (PSR) map with a resolution of 240 m per pixel and a digital elevation model with a resolution of 240 m per point, which is interpolated from a source with a resolution of 60 m per pixel and meshed with triangles by the Thermal Moon Simulator (TherMoS) tool in order to calculate illumination values. The requirements chosen for the candidate landing sites are a slope of less than 5° over a diameter of at least 1 km and having both a PSR and a Peak of Light (POL) in less than 10 km distance. We discuss the four most promising candidate sites in this paper and calculate initial energy storage system estimates to select two landing sites for further analysis.We derive a reaction kinetics model for the ilmenite hydrogen reduction ISRU process from literature data and incorporate it into a dynamic model with simulated lighting and thermal conditions to calculate heat losses to the environment and the required electrical energy for its operation. In addition, we use the derived model to analyze and compare different design options of the ISRU reactor with an Equivalent System Mass (ESM) based optimization approach to identify the optimal operating conditions. Using this approach, we found operating temperatures above 1150 K resulted in higher ESM values for the reactor than lower temperatures.For the Moon base, we combine an ISS ECLSS model and the ISRU reactor model. The state-of-the-art urine and water processing technologies achieve recovery rates of up to 98%. Hence, we expect the overall ECLSS including the ISRU reactor to have a water surplus when combined with a Sabatier reactor to process metabolic CO2 from the crew into methane and water. Therefore, the Sabatier reactor combined with an electrolyzer can potentially generate methane and oxygen as fuel for resupply missions. The system can achieve a theoretic fuel production of 4100 kg per year using this approach. Although the dynamic analysis showed that only 2588 kg could be produced per year because of the lean operating conditions of the Sabatier and its efficiency of below 100%. The produced oxygen and methane could reduce operating costs for the base by reducing the required fuel resupply. Based on the power demands of the other subsystems and the available solar power and shadow duration at the selected landing site, we dimensioned the RFCS and estimate the required mass for it to 19,500 kg. Which is less than half the mass required if lithium batteries are used. The overall system requires resupply of approximately 6580 kg per year for a crew of six. The dynamic analysis of the system showed that the initial mostly steady state sizing approach can be optimized and relevant system parameters can be reduced by more than 15%.

Trajectory Design of Perseus: A CubeSat Mission Concept to Phobos

The Martian satellites Phobos and Deimos hold many unanswered questions that may provide clues to the origin of Mars. These moons are low Δv stopover sites to Mars. Some human missions to Mars typically identify Phobos and Deimos as staging bases for Mars surface exploration. Astronauts could base initial operations there in lieu of repeated voyages to and from the planet surface, to refuel transiting spacecraft, to teleoperate robotics and other critical machinery, and to develop habitable infrastructure ahead of human landings. Despite their strategic and scientific significance, there has been no successful dedicated mission to either moon. For this reason, we propose Perseus, a geological imaging CubeSat mission to Phobos. Perseus, a 27U, 54kg CubeSat will return thermal and visible images at resolutions better than currently available over most of Phobos’ surface. This includes visible images at 5m/pixel and thermal images at 25m/pixel of Phobos’ surface. The Perseus mission is nominally intended to be a co-orbital mission, where the spacecraft will encounter Phobos on its Martian orbit. However, a hyperbolic rendezvous mission concept, to image Phobos on a hyperbolic flyby, is also considered to reduce the risks associated with orbit capture and to reduce mission costs. This paper presents the preliminary feasibility, science objectives, and technological development challenges of achieving these science goals. We then formulate two rendezvous concepts as a series of three nonlinear optimization problems that span the design tree of mission concepts. The tree’s root node is the heliocentric cruise problem, which identifies the near-optimal launch and arrival windows for the Perseus spacecraft. The leaf nodes of the design tree are the two rendezvous concepts that identify near-optimal co-orbital and hyperbolic trajectories for Phobos’ reconnaissance. The design problems are solved using evolutionary algorithms, and the performance of the selected mission concepts is then examined. The results indicate that a co-orbital encounter allows about one encounter per day with about 6 min per encounter. The hyperbolic encounter, on the other hand, allows a single encounter where the spacecraft will spend about 2 min in the imaging region with respect to Phobos. The spacecraft will obtain higher resolution images of Phobos on this feasible region than have ever been seen for most of the surface. These detailed images will help identify candidate landing sites and provide critical data to derisk future surface missions to Phobos.

Hayabusa2 Landing Site Selection: Surface Topography of Ryugu and Touchdown Safety

One of the primary goals of Hayabusa2 is to land on the asteroid Ryugu to collect its surface materials. The key for a successful touchdown is to find a promising landing site that meets both scientific and engineering requirements. Due to the limited availability of pre-arrival information about Ryugu, the landing site selection (LSS) must be conducted based on proximity observations over a limited length of time. In addition, Ryugu was discovered to possess an unexpectedly high abundance of boulders with an absence of wide and flat areas, further complicating the LSS. To resolve these problems, we developed a systematic and stepwise LSS process with a focus on the surface topography of Ryugu and the associated touchdown safety. The proposed LSS scheme consists of two phases: Phase-I LSS, a comprehensive survey of potential landing areas at the 100-m scale based on the global mapping of Ryugu, and Phase-II LSS, a narrowing-down process of the candidate landing sites at the 10-m scale using high-resolution images and a local terrain model. To verify the feasibility of a precision landing at the target site, we also investigated the landing dispersion via a Monte Carlo simulation, which incorporates the effect of the irregular surface gravity field. One of the major characteristics of the Hayabusa2 LSS developed in this study is the iterative feedback between LSS analyses on the ground and actual spacecraft operations near the target asteroid. Using the newly developed method, we chose a landing site with a radius of 3 m, and Hayabusa2 successfully conducted its first touchdown on February 21, 2019. This paper reports the methodology and results of the stepwise iterative LSS for the first Hayabusa2 touchdown. The touchdown operation results reconstructed from flight data are also provided, demonstrating the validity of the adopted LSS strategy.

A local Martian crustal field model: Targeting the candidate landing site of the 2020 Chinese Mars Rover

Unlike Earth, Mars lacks a global dipolar magnetic field but is dominated by patches of a remnant crustal magnetic field. In 2021, the Chinese Mars Rover will land on the surface of Mars and measure the surface magnetic field along a moving path within the possible landing region of 20°W–50°W, 20°N–30°N. One scientific target of the Rover is to monitor the variation in surface remnant magnetic fields and reveal the source of the ionospheric current. An accurate local crustal field model is thus considered necessary as a field reference. Here we establish a local crust field model for the candidate landing site based on the joint magnetic field data set from Mars Global Explorer (MGS) and Mars Atmosphere and Volatile Evolution (MAVEN) data combined. The model is composed of 1,296 dipoles, which are set on three layers but at different buried depths. The application of the dipole model to the joint data set allowed us to calculate the optimal parameters of their dipoles. The calculated results demonstrate that our model has less fitting error than two other state-of-the art global crustal field models, which would indicate a more reasonable assessment of the surface crustal field from our model.

Illumination and temperature analysis for CE-5 candidate landing site Mons Rümker

The forthcoming lunar exploration of Chang’e-5 (CE-5) mission will be the first sampling return project of China. The actual drilling needs the information about real-time illumination and corresponding temperature. To give a support for the project, in this paper the SPICE software system is first used to calculate the real-time illumination at the CE-5 candidate landing site Mons Rümker. It is found that our synthetic map of illumination is consistent with the morning map of illumination provided by the Japan’s SELENE satellite. This result verifies the rationality of our algorithm and the corresponding code. According to the calculated illumination and considering a one-dimensional heat conduction model, we study the temperature distribution over Mons Rümker. It is found that the regolith temperature near the surface is greatly related to the illumination, but varies a little with the depth increasing. It is also discovered that the regolith temperature beneath a depth of 0.57 m will not change any more. To give a support for the actual drilling program, it is recommended to consider the temperature difference between the outside and inside of the regolith, especially their stresses caused by such a temperature difference. Moreover, considering the drilling depth of CE-5 larger than 0.57 m, it is likely to measure the heat flow for the constant-temperature layer. We propose that for the next lunar exploration following CE-5 the measurement of heat flow is considered. This will promote the research of lunar science.