Lander Mission Research Articles

Informing Planetary Protection Policies for the Future Exploration of Ceres: State of Understanding after the Dawn Mission.

We review the current state of understanding of Ceres as it relates to planetary protection policy for future landed missions, including for sample return, to the dwarf planet. The Dawn mission found Ceres to be an intriguing target for a mission, with evidence for the presence of regional, possibly extensive liquid at depth, and local expressions of recent and potentially ongoing activity. The Dawn mission also found a high abundance of carbon in the regolith, interpreted as a mix of carbonates and amorphous carbon, as well as locally high concentrations of organic matter. Key findings from this review are as follows: (1) outside of the region of Occator crater, Ceres shows no geological evidence for conduits from the surface to the interior; and (2) considering the biological potential of Ceres' deep interior, a surface sample return mission should be considered Category V restricted, unless it can be demonstrated that evaporites sourced from Ceres' deep brine region, and recently exposed in Occator crater, have not been scattered to the rest of Ceres' surface; in that case, the probability of returning an unsterilized particle to an acceptably low value is to be determined by a future study.

Comprehensive characterization of solar wind interaction with lunar crustal magnetic fields: Kaguya low-altitude observations

Although the Moon does not have a global intrinsic magnetic field, lunar crustal magnetic anomalies (LMAs) are nonuniformly distributed over the lunar surface. The interaction between the solar wind and LMAs leads to the formation of mini-magnetospheres. Since the spatial scales of LMAs are very small, below several tens of kilometers, solar wind ions are demagnetized while electrons are still magnetized, forming Hall electric fields typically at low altitudes (<∼30 km). Since direct observations of these interaction regions are challenging from typical nominal altitudes of lunar orbiters (>∼\\sim$$\\end{document}]]>100 km), the solar wind-LMA interaction has not been fully understood. In this study, we analyze low-altitude data obtained by Kaguya over various LMAs to comprehensively characterize the plasma environment and electromagnetic fields in the solar wind-LMA interaction region. We observe strong solar wind ion reflection and whistler mode waves at 1–10 Hz under high solar wind dynamic pressure and strong interplanetary magnetic field conditions, respectively. These trends are particularly clear over spatially extended LMAs. Over both spatially isolated and extended LMAs, strong Broadband Electrostatic Noise at 1–10 kHz tends to be observed when the spacecraft is magnetically connected to the lunar surface. In addition, our results suggest that anti-moonward electrostatic fields at low altitudes contribute to the acceleration, deceleration, and reflection of incident solar wind particles, and the resulting modification of particle velocity distribution functions can strongly influence the nature of the solar wind-LMA interaction including plasma wave excitation. Based on Kaguya data, we also develop a predictable indicator of the central interaction region where solar wind ions and electrons are decoupled. We propose that this indicator can be utilized to define regions of interest for future low-altitude or lander missions to LMA.Graphical

Simulation of the charged particle deflection from the sweeping magnet array in the Lunar Environment heliospheric X-ray imager.

The Lunar Environment heliospheric X-ray Imager (LEXI) is an instrument built to image x-rays from solar wind charge exchange in Earth's magnetosheath. Monitoring the position of the magnetopause at the inner boundary of the magnetosheath allows us to understand how magnetic reconnection regulates how energy from the solar wind is deposited into Earth's magnetosphere. LEXI is part of an upcoming lunar lander mission set to land in Mare Crisium. To repel unwanted charged particles, the instrument carries a permanent magnet array composed of 48 neodymium magnets. The array was designed to maximize charged particle deflection while minimizing stray magnetic fields, which could impact other instruments or spacecraft operation. A Runge-Kutta-based fully kinetic particle tracing model was created to evaluate the effectiveness of LEXI's unique charged particle deflector array. Combined with the other particle suppression measures of the instrument, including physical structures and filters, the simulations show proton and electron transmission to the LEXI detector is expected to be sufficiently reduced to allow successful imaging. The flexible simulation model can be generalized to be used in examining the magnetic deflector array effectiveness of other instruments whose signals could be compromised by unwanted charged particle contamination.

Utility-Driven Approach to Onboard Scheduling and Execution for an Autonomous Europa Lander Mission

Jupiter’s icy moon Europa is among the most promising locations to explore for signs of extraterrestrial life in our solar system. However, searching for biosignatures on the surface of Europa presents an unprecedented set of challenges: immense uncertainty, limited energy, and few opportunities for operator feedback. Effectively carrying out a robotic science campaign under these conditions will require a system with a greater degree of autonomy than any planetary exploration mission to date. In particular, onboard scheduling and execution are required for robustness to uncertainty in surface conditions, variation in lander performance, and science discoveries to maximize the quantity and quality of science data returned to Earth during a fixed, limited lander lifetime. Here we represent a proposed Europa Lander surface mission as a utility-driven hierarchical task network and establish through analysis that onboard autonomy using automated mission planning with execution feedback and predictive task models results in mission execution that is more consistently productive compared to traditional static approaches. We design a simulated onboard autonomy framework built by integrating two software components—Multi-mission EXECutive and Europa Lander Autonomy Prototype—to properly simulate the Europa Lander domain and demonstrate empirically that the proposed planning and execution system is capable of commanding a set of realistic surface scenarios as part of a larger Europa Lander surface autonomy software prototype. We expect that an approach to scheduling and execution grounded in decision theory will be an enabling technology for future tightly constrained planetary surface missions.

A fast calculation method for three-impulse contingency return trajectory during the near-moon phase based on differential algebra

Aimed at the demand of contingency return at any time during the near-moon phase in the manned lunar landing missions, a fast calculation method for three-impulse contingency return trajectories is proposed. Firstly, a three-impulse contingency return trajectory scheme is presented by combining the Lambert transfer and maneuver at the special point. Secondly, a calculation model of three-impulse contingency return trajectories is established. Then, fast calculation methods are proposed by adopting the high-order Taylor expansion of differential algebra in the two-body trajectory dynamics model and perturbed trajectory dynamics model. Finally, the performance of the proposed methods is verified by numerical simulation. The results indicate that the fast calculation method of two-body trajectory has higher calculation efficiency compared to the semi-analytical calculation method under a certain accuracy condition. Due to its high efficiency, the characteristics of the three-impulse contingency return trajectories under different contingency scenarios are further analyzed expeditiously. These findings can be used for the design of contingency return trajectories in future manned lunar landing missions.

Comprehensive Analysis of a Chloride‐Rich Topographic Depression in Terra Sirenum, Mars: A Possible Lost Basin With Astrobiological Significance

AbstractThe hygroscopic nature of chlorides gives them the potential to provide a harbor for microbes to adapt and survive in extreme conditions, which is pertinent to Mars, given its evolution of climatic conditions. Moreover, observations of secondary hydrous minerals in chloride‐rich regions have opened the case for a diverse geological environment on the Martian surface. Therefore, through comprehensive analysis, we aim to reconstruct the geological evolution of a chloride‐rich basin within Terra Sirenum. We conducted morphological, morphometric, and mineralogical analyses of the basin and its surrounding area to determine its geological evolution, longevity, and environmental condi5tions during its activity. Subsequently, we carried out a discharge analysis of the surrounding valley networks and determined the water activity using ionic forms of the associated mineralogy. We observed bright‐toned polygonal cracks within the basin as well as its surrounding terrain, suggesting that the basin extended beyond its present boundary. Mineralogical diversity and age dating of the basin and the surrounding area indicated different geochemical environments and cycles of wetting and drying until the late Hesperian. Whereas, sediment transport modeling suggests that the basin was hydrologically active for more than ten thousand years. Our results show a tell‐tale signature of a large sedimentary basin and a large‐scale geological process within the Terra Sirenum. The water activity modeling show that the geochemical composition of the basin was favorable to support the origin of life forms and/or sustain them and suggest promising aspects of the basin for future landing missions.

MEDEA: A New Model for Emulating Radio Antenna Beam Patterns for 21 cm Cosmology and Antenna Design Studies

In 21 cm experimental cosmology, accurate characterization of a radio telescope’s antenna beam response is essential to measure the 21 cm signal. Computational electromagnetic (CEM) simulations estimate the antenna beam pattern and frequency response by subjecting the EM model to different dependencies, or beam hyperparameters, such as soil dielectric constant or orientation with the environment. However, it is computationally expensive to search all possible parameter spaces to optimize the antenna design or accurately represent the beam to the level required for use as a systematic model in 21 cm cosmology. We therefore present the Model for Emulating Directivities and Electric fields of Antennas (MEDEA), an emulator that rapidly and accurately generates far-field radiation patterns over a large hyperparameter space. MEDEA takes a subset of beams simulated by CEM software, spatially decomposes them into coefficients on a complete, linear basis, and then interpolates them to form new beams at arbitrary hyperparameters. We test MEDEA on an analytical dipole and two numerical beams motivated by upcoming lunar lander missions, and then employ MEDEA as a model to fit mock radio spectrometer data to extract covariances on the input beam hyperparameters. We find that the interpolated beams have rms relative errors of at most 10−2 using 20 input beams or less, and that fits to mock data are able to recover the input beam hyperparameters when the model and mock are derived from the same set of beams. When a systematic bias is introduced into the mock data, extracted beam hyperparameters exhibit bias, as expected. We propose several extensions to MEDEA to potentially account for such bias.

Observed Correlation Between Local Topography and Passive Neutron Measurements From the Dynamic Albedo of Neutrons (DAN) Instrument on the Mars Science Laboratory (MSL) Rover

AbstractThe Dynamic Albedo of Neutrons (DAN) instrument on the Mars Science Laboratory Curiosity rover primarily measures neutrons that have undergone interactions with rocks and materials in the rover's local environment. As the rover ascends Aeolis Mons, it may encounter more extreme local topography (e.g., cliffs, gullies, canyons). We present three parts of the rover's traverse in which local topography, expressed as the average local relief relative to the rover, is moderately to strongly correlated with an increase in passive thermal neutron count rates. These increases in count rates are consistent with results from radiation transport models of the instrument's performance near simulated topographic features. Additional DAN measurements in areas of high average local relief (&gt;0.25 m) within 5 m of the instrument could bolster this correlation. DAN's sensitivity to topography in its passive mode could be utilized as a new measurement capability and has implications for the operation of future landed missions carrying neutron spectrometers (e.g., VIPER, MoonRanger, Lunar‐VISE).

A New Robust Lunar Landing Selection Method Using the Bayesian Optimization of Extreme Gradient Boosting Model (BO-XGBoost)

The safety of lunar landing sites directly impacts the success of lunar exploration missions. This study develops a data-driven predictive model based on machine learning, focusing on engineering safety to assess the suitability of lunar landing sites and provide insights into key factors and feature representations. Six critical engineering factors were selected as constraints for evaluation: slope, elevation, roughness, hillshade, optical maturity, and rock abundance. The XGBoost model was employed to simulate and predict the characteristics of landing areas and Bayesian optimization was used to fine-tune the model’s key hyperparameters, enhancing its predictive performance. The results demonstrate that this method effectively extracts relevant features from multi-source remote sensing data and quantifies the suitability of landing zones, achieving an accuracy of 96% in identifying landing sites (at a resolution of 0.1° × 0.1°), with AUC values exceeding 95%. Notably, slope was recognized as the most critical factor affecting safety. Compared to assessment processes based on Convolutional Neural Networks (CNNs) and Random Forest (RF) models, XGBoost showed superior performance in handling missing values and evaluating feature importance accuracy. The findings suggest that the BO-XGBoost model shows notable classification performance in evaluating the suitability of lunar landing sites, which may provide valuable support for future landing missions and contribute to optimizing lunar exploration efforts.

Intelligent cooperative control for flexible landing on small celestial bodies

In view of the potential landing risks in small celestial body landing missions, the concept of flexible landing has been proposed in recent years. By employing a flexible lander with structural compliance to complex surface topography, the risks of rebound or overturning upon touchdown can be reduced. During flexible landing, the overall motion of the flexible lander is controlled by several nodes embedded in the flexible structure. Due to the flexible deformation, the motion among the nodes is intricately coupled, posing challenges to the control algorithm design. To address this problem, an intelligent cooperative control method for flexible landing is proposed in this paper. By decomposing the flexible internal force into a low-order principal term with specific physical interpretation and an unmodeled high-order residual term, the coupling relationship among the nodes is characterized. On this basis, the low-order dynamics system is reconstructed into a piecewise affine system, upon which a multi-node cooperative optimal controller is designed. A long-short-term memory recurrent neural network is further established to compensate for the unmodeled high-order term. Through the combination of the low-order principal control and the high-order intelligent compensation, a feasible approach for achieving flexible landing is obtained. Finally, the effectiveness of the proposed control method is verified via 433 Eros-based flexible landing simulations.

Organ dose equivalents of albedo protons and neutrons under exposure to large solar particle events during lunar human landing missions

Astronauts participating in lunar landing missions will encounter exposure to albedo particles emitted from the lunar surface as well as primary high-energy particles in the spectra of galactic cosmic rays (GCRs) and solar particle events (SPEs). While existing studies have examined particle energy spectra and absorbed doses in limited radiation exposure scenarios on and near the Moon, comprehensive research encompassing various shielding amounts and large SPEs on the lunar surface remains lacking. Additionally, detailed organ dose equivalents of albedo particles in a human model on the lunar surface have yet to be investigated. This work assesses the organ dose equivalents of albedo neutrons and albedo protons during historically large SPEs in August 1972 and September 1989 utilizing realistic computational anthropomorphic human phantom for the first time. Dosimetric quantities within human organs have been evaluated based on the PHITS Monte Carlo simulation results and quality factors of the state-of-the-art NASA Space Cancer Risk (NSCR) model, as well as ICRP publications. The results with the NSCR model indicate that the albedo contribution to organ dose equivalent is less than 3 % for 1 g/cm2 aluminum shielding, while it increases to more than 30 % in some organs for 50 g/cm2 aluminum shielding during exposure to low-energy-proton-rich SPEs.

Geological evidence for extensive basin ejecta as plains terrains in the Moon’s South Polar Region

Water ice and other volatiles that accumulated in the Moon’s polar regions are among the top priority targets for lunar exploration, due to their significances in both lunar geology and extraterrestrial resource utilization. Locating suitable landing sites and determining the provenance of sampled/measured surface materials are critical for future landed missions. Here, we map over 800 sites of plains terrains in the Moon’s south polar region, with a total surface area of ~46,000 km2. Orbital measurements and analog studies show that most of these plains have apparently higher albedo and lower iron content than volcanic mare plains, suggesting an origin of ejecta-induced debris flows from distant impact craters, especially from the Schrödinger basin. Our findings suggest that the entire lunar south polar region probably have experienced contributions from distant basin materials. We recommend these plains as priority landing sites for future exploration of lunar polar volatiles and early bombardment history.

Radiolytic Effects on Biological and Abiotic Amino Acids in Shallow Subsurface Ices on Europa and Enceladus.

Europa and Enceladus are key targets to search for evidence of life in our solar system. However, the surface and shallow subsurface of both airless icy moons are constantly bombarded by ionizing radiation that could degrade chemical biosignatures. Therefore, sampling of icy surfaces in future life detection missions to Europa and Enceladus requires a clear understanding of the necessary ice depth where unaltered organic biomolecules might be present. We conducted radiolysis experiments by exposing individual amino acids in ices and amino acids from dead microorganisms in ices to gamma radiation to simulate conditions on these icy worlds. In the pure amino acid samples, glycine did not show a detectable decrease in abundance, whereas the abundance of isovaline decreased by 40% after 4 MGy of exposure. Amino acids in dead Escherichia coli (E. coli) organic matter exhibited a gradual decline in abundances with the increase of exposure dosage, although at much slower rates than individual amino acids. The majority of amino acids in dead A. woodii samples demonstrated a step function decline as opposed to a gradual decline. After the initial drop in abundance with 1 MGy of exposure, those amino acids did not display further decreases in abundance after exposure up to 4 MGy. New radiolysis constants for isolated amino acids and amino acids in dead E. coli material for Europa/Enceladus-like conditions have been derived. Slow rates of amino acid destruction in biological samples under Europa and Enceladus-like surface conditions bolster the case for future life detection measurements by Europa and Enceladus lander missions. Based on our measurements, the "safe" sampling depth on Europa is ∼20 cm at high latitudes of the trailing hemisphere in the area of little impact gardening. Subsurface sampling is not required for the detection of amino acids on Enceladus-these molecules will survive radiolysis at any location on the Enceladus surface. If the stability of amino acids observed in A. woodii organic materials is confirmed in other microorganisms, then the survival of amino acids from a potential biosphere in Europa ice would be significantly increased.

Conceptual Design of an Unmanned Electrical Amphibious Vehicle for Ocean and Land Surveillance

Unmanned vehicles (UVs) have become increasingly important in various scenarios of civil and military operations. The present work aims at the conceptual design of a modular Amphibious Unmanned Ground Vehicle (A-UGV) that can be easily adapted for different types of land and/or water missions with low monetary cost (EUR &lt; 5 k, without sensors). Basing the design on the needs highlighted in the 2021 review of the Strategic Directive of the Portuguese Navy, the necessary specifications and requirements are established for two mission scenarios. Then, a market research analysis focused on vehicles currently available and their technological advances is conducted to identify existing UV solutions and respective characteristics/capabilities of interest to the current work. To study and define the geometry of the hull and the configuration of the A-UGV itself, preliminary computational structural and fluid analyses are carried out to ensure it complies with the specifications initially established. As a result, one obtains a fully electric vehicle with approximate dimensions of 1050 × 670 × 450 mm (length–width–height), enabled with 6 × 6 traction capable of reaching 20 km/h on land, which possesses amphibious capabilities of independent propulsion in water up to 8 kts and an estimated autonomy of over 60 min.

Tripping on the Moon

Two recent lunar lander missions have toppled over on touchdown. We analyse a simplified model to determine the lateral speed of an object that results in tipping, as a practical example of an inelastic collision that conserves angular momentum. The solution employs rotational dynamics and conservation laws covered in an introductory mechanics course. We suggest further investigations, including simple experiments that can be performed in the teaching laboratory.

Optimal attitude control for landing on asteroid with a flexible lander

The recently developed flexible lander offers a potential option for future asteroid landing missions due to its advantages in suppression of rebound and overturning. The strong nonlinear dynamics and control constraints of the flexible lander hinder the online implementation of optimal attitude feedback control. To generate the optimal attitude control rapidly, a constrained inhomogeneous approximating sequence of Riccati equations (CI-ASRE) method is proposed. The saturation function is firstly constructed to incorporate control magnitude constraints into dynamics so that the constraints can be analytically handled. Subsequently, to avoid singularity, a partial factorization strategy is proposed to convert the constrained dynamics into two parts, a pseudolinear term and an inhomogeneous term. This factorization enables the nonlinear problem to be expressed as the limit of a sequence of inhomogeneous linear quadratic problems while avoiding local linearization. At last, the analytical CI-ASRE is newly derived to iteratively solve these problems to rapidly obtain optimal feedback control. The computational simplicity and effectiveness of the CI-ASRE method overcome difficulties of optimal attitude control problems of the flexible lander associated with control constraints, strong nonlinearity, and online feedback control generation. The effectiveness of the proposed method for the flexible lander is verified using a landing scenario on asteroid 433 Eros.

Perseverance MEDA Atmospheric Pressure Observations—Initial Results

AbstractThe Mars2020 Perseverance Rover landed successfully on the Martian surface on the Jezero Crater floor (18.44°N, 77.45°E) at Martian solar longitude, Ls, ∼5° in February 2021. Since then, it has produced highly valuable environmental measurements with a versatile scientific payload including the MEDA (Mars Environmental Dynamics Analyzer) suite of environmental sensors. One of the MEDA systems is the PS pressure sensor system, which weighs 40 g and has an estimated absolute accuracy of better than 3.5 Pa and a resolution of 0.13 Pa. We present initial results from the first 414 sols of Martian atmospheric surface pressure observations by the PS, whose performance was found to meet its specifications. Observed sol‐averaged atmospheric pressures follow an anticipated pattern of pressure variation in the course of the advancing season and are consistent with data from other landing missions. The observed daily pressure amplitude varies by ∼2%–5 % of the sol‐averaged pressure, with absolute amplitude 10–35 Pa in an approximately direct relationship with airborne dust. During a regional dust storm, which began at Ls ∼ 135°, the daily pressure amplitude roughly doubled. The daily pressure variations were found to be remarkably sensitive to the seasonal evolution of the atmosphere. In particular, analysis of the daily pressure signature revealed diagnostic information likely related to the regional scale structure of the atmosphere. Comparison of Perseverance pressure observations with data from other landers reveals the global scale seasonal behavior of Mars' atmosphere.

Multi-Objective Robust Trajectory Design for Powered Descent and Landing

A robust trajectory optimization approach for guidance algorithm gain and target vector selection for powered descent and landing is developed. A genetic algorithm is used to determine optimized guidance algorithm parameters to minimize the impact of initial condition, environment, navigation, and vehicle property uncertainty on flight performance for a given sensor suite. Vehicle state uncertainties are computed efficiently using linear covariance analysis techniques. When implemented in the guidance algorithm, the optimized gains and target vectors shape a trajectory that has more favorable conditions for a given navigation sensor suite, resulting in improved flight performance. As a demonstration of this method, the optimized guidance parameters are found for a multiphase trajectory from powered descent initiation to touchdown for a robotic lunar landing mission. Single-objective optimization results demonstrate a reduction in uncertainty and an improvement in nominal performance. Multi-objective optimization results showing the tradeoff between terminal position uncertainty and total propellant usage are presented for multiple sensor suite compositions. Further, guidance parameters selected using the developed robust trajectory design approach may enable acceptable flight performance with fewer and/or lower-quality sensors. The resulting Pareto fronts present the optimal trade space early in the mission design process to enable informed decision-making.

Whipple’s Vision: Theology of the Land and Nineteenth-Century Episcopal Missions to Minnesota Native Americans

This article considers theologies of the land by examining the legacy of the nineteenth-century Episcopal bishop Henry Benjamin Whipple and his encounter with Minnesota’s Native American people. Using the work of Willie James Jennings as an interpretive lens, it argues that Whipple developed and implemented a theology in which land is (1) fundamentally separate from people, (2) passive physical material, (3) a resource for human productivity, and (4) an instrument for the formation of Christian and American identity. It shows how such a vision of the land has contributed to a destructive theology of displacement, conquest, wealth, and assimilation. It briefly proposes an alternative theology of the land in which land is (1) distinguishable but not separable from people, (2) differentiated and sacred, (3) a creature with value exceeding its productivity, and (4) a place for mutual formation of people and land through God’s power.

High frequency Lunar Penetrating Radar quality control, editing and processing of Chang’E-4 lunar mission

Chinese lunar landing mission Chang’E-4 reached the far side of the Moon in January 2019 and has been providing unprecedented Lunar Penetrating Radar data able to explore the lunar subsurface down to more than 40 m (with its more resolutive high frequency band). Data are periodically released to the scientific community in raw PDS4 format. Here we provide different versions of the radar dataset after editing (i.e. pre-processing), partial, and full processing in order to provide a complete ready-to-use dataset to end-users (data collected since 4th January 2019 until 27th March 2023) which can be directly exploited for analysis, interpretation, inversion, as well as integration with imagery or other information. In particular, we implemented an efficient and objective way to remove duplicated traces representing more than 90% of original data, as well as a processing flow able to retain all the original data information, while avoiding redundancies. The provided datasets can be implemented with future data releases and straightforwardly exploited for any future analysis.