near-Earth Research Articles

The Oxygen Isotopic Composition of Samples Returned from Asteroid Ryugu with Implications for the Nature of the Parent Planetesimal

We present oxygen isotopic analyses of fragments of the near-Earth Cb-type asteroid Ryugu returned by the Hayabusa2 spacecraft that reinforce the close correspondence between Ryugu and CI chondrites. Small differences between Ryugu samples and CI chondrites in can be explained at least in part by contamination of the latter by terrestrial water. The discovery that a randomly sampled C-complex asteroid is composed of CI-chondrite-like rock, combined with thermal models for formation prior to significant decay of the short-lived radioisotope 26Al, suggests that if lithified at the time of alteration, the parent body was small (≪50 km radius). If the parent planetesimal was large (>50 km in radius), it was likely composed of high-permeability, poorly lithified sediment rather than consolidated rock.

The Large Array Survey Telescope—Science Goals

The Large Array Survey Telescope (LAST) is designed to survey the variable and transient sky at high temporal cadence. The array is comprised of 48 F/2.2 telescopes of 27.9 cm aperture, coupled to full-frame backside-illuminated cooled CMOS detectors with 3.76 μm pixels, resulting in a pixel scale of 1.″25. A single telescope with a field of view of 7.4 deg2 reaches a 5σ limiting magnitude of 19.6 in 20 s. LAST 48 telescopes are mounted on 12 independent mounts—a modular design which allows us to conduct optimized parallel surveys. Here we provide a detailed overview of the LAST survey strategy and its key scientific goals. These include the search for gravitational-wave (GW) electromagnetic counterparts with a system that can cover the uncertainty regions of the next-generation GW detectors in a single exposure, the study of planetary systems around white dwarfs, and the search for near-Earth objects. LAST is currently being commissioned, with full scientific operations expected in mid 2023. This paper is accompanied by two complementary publications in this issue, giving an overview of the system and of the dedicated data reduction pipeline.

Determination of the Motion Parameters of Near-Earth Objects from Position Measurements Performed at the Terskol Observatory

Determination of the Motion Parameters of Near-Earth Objects from Position Measurements Performed at the Terskol Observatory

Conceptual Design of Near-Earth Asteroid Mining and Utilization of Potential Resources

Asteroid mining represents a groundbreaking endeavor with the potential to revolutionize resource acquisition and pave the way for sustainable space exploration. This conceptual research paper explores the scientific and technological aspects of asteroid mining, focusing on its feasibility, potential benefits, and challenges. By analyzing existing missions, advancements in robotics and spacecraft technologies, and resource prospecting techniques, this paper aims to shed light on the transformative impact of asteroid mining on resource sustainability and the future of space exploration.

Close encounters of the interstellar kind: exploring the capture of interstellar objects in near-Earth orbit

ABSTRACT Recent observations and detections of interstellar objects (ISOs) passing through the Solar system have sparked a wave of interest into these objects. Although rare, these ISOs can be captured into bound orbits around the Sun. In this study, we investigate the novel idea of capture of ISOs into near-Earth orbits and find that a steady population of ISOs exists among the current population of near-Earth objects (NEOs). Using numerical simulations, we find that the capture of ISOs into near-Earth orbits is dominated by Jupiter that is 104 times more efficient in capturing ISOs compared to Earth. Captured ISOs are more likely to be in orbits with high eccentricities and low inclinations. We also investigate the stability of captured ISOs and find that they are generally unstable and have an average survival lifetime of ∼1 Myr, consistent with lifetime of NEOs originating from outer asteroid belt, and are ejected from the Solar system due to interactions with other planets or the Sun. Our results have important implications for understanding the population of ISOs in the Solar system and possible future detection. We find that about one to a few 50–70 m sized captured ISOs among NEOs would be detectable by Vera Rubin Observatory over its lifetime. By detecting and studying captured ISOs, we can learn about the properties and origins of such objects, and the formation and evolution of exoplanetary systems and even our Solar system.

The path towards increasing RAMS for novel complex missions based on CubeSat technology

The paper presents the initial outcomes of a project, currently ongoing under the supervision of the European Space Agency, having the main objective to specify and design a Fault Detection Isolation and Recovery (FDIR) system by making use of relevant RAMS (Reliability, Availability, Maintainability, Safety) analyses for missions in non-deterministic environment with limited resources. The initial project tasks have been to select a study case represented by a CubeSat complex mission, analyse in detail both its mission and system requirements and, based on them, define a set of relevant RAMS analyses to be carried out in the second phase of the project, as inputs for the development of a FDIR concept aimed at a careful balance of the limited spacecraft resources in case of critical failures. Two possible study cases have been identified: LUMIO, a 12U CubeSat mission for the observation of micro-meteoroid impacts on the Lunar farside, and M-ARGO, a 12U deep-space CubeSat which will rendezvous with a near-Earth asteroid and characterize its physical properties for the presence of in-situ resources. Although both missions are characterized by a high level of autonomy and complexity in a harsh environment, LUMIO has been eventually selected as study case for the project. In the paper, the challenges and features of this mission are shortly presented. The specificities of the RAMS analysis and FDIR concept for this specific class of small satellite missions (including the selected study case) are highlighted in the paper, looking in particular at aspects such as the improvement of reliability while maintaining the CubeSat philosophy, the tuning of mission and system requirements in view of facilitating the design and implementation of the FDIR concept, and the current gaps within the RAMS/FDIR body of knowledge. The conclusions drawn during this first project phase provide a real view of how systems engineering must work in tandem with RAMS analyses and FDIR to achieve a more robust and functional mission architecture, thus improving the mission reliability.

NEOMOD: A New Orbital Distribution Model for Near-Earth Objects

Near-Earth Objects (NEOs) are a transient population of small bodies with orbits near or in the terrestrial planet region. They represent a mid-stage in the dynamical cycle of asteroids and comets, which starts with their removal from the respective source regions—the main belt and trans-Neptunian scattered disk—and ends as bodies impact planets, disintegrate near the Sun, or are ejected from the solar system. Here we develop a new orbital model of NEOs by numerically integrating asteroid orbits from main-belt sources and calibrating the results on observations of the Catalina Sky Survey. The results imply a size-dependent sampling of the main belt with the ν 6 and 3:1 resonances producing ≃30% of NEOs with absolute magnitudes H = 15 and ≃80% of NEOs with H = 25. Hence, the large and small NEOs have different orbital distributions. The inferred flux of H < 18 bodies into the 3:1 resonance can be sustained only if the main-belt asteroids near the resonance drift toward the resonance at the maximal Yarkovsky rate (≃2 × 10−4 au Myr−1 for diameter D = 1 km and semimajor axis a = 2.5 au). This implies obliquities θ ≃ 0° for a < 2.5 au and θ ≃ 180° for a > 2.5 au, both in the immediate neighborhood of the resonance (the same applies to other resonances as well). We confirm the size-dependent disruption of asteroids near the Sun found in previous studies. An interested researcher can use the publicly available NEOMOD Simulator to generate user-defined samples of NEOs from our model.

Avoiding Armageddon The urgent search for near-Earth objects

Avoiding Armageddon The urgent search for near-Earth objects

Astreaks: astrometry of NEOs with trailed background stars

ABSTRACT The detection and accurate astrometry of fast-moving near-Earth objects (NEOs) has been a challenge for the follow-up community. Their fast apparent motion results in streaks in sidereal images, thus affecting the telescope’s limiting magnitude and astrometric accuracy. A widely adopted technique to mitigate trailing losses is non-sidereal tracking, which transfers the streaking to background reference stars. However, no existing publicly available astrometry software is configured to detect such elongated stars. We present Astreaks, a streaking source detection algorithm, to obtain accurate astrometry of NEOs in non-sidereal data. We validate the astrometric accuracy of Astreaks on 371 non-sidereally tracked images for 115 NEOs with two instrument set-ups of the GROWTH-India Telescope. The observed NEOs had V-band magnitude in the range [15, 22] with proper motion up to 140 arcsec min−1, thus resulting in stellar streaks as high as 6.5 arcmin (582 pixels) in our data. Our method obtained astrometric solutions for all images with 100 per cent success rate. The standard deviation in observed-minus-computed (O–C) residuals is 0.52 arcsec with O–C residuals &amp;lt;2 arcsec (&amp;lt;1 arcsec) for 98.4 per cent (84.4 per cent) of our measurements. These are appreciable, given the pixel scale of ∼0.3 and ∼0.7 arcsec of our two instrument set-ups. This demonstrates that our modular and fully automated algorithm helps improve the telescope system’s limiting magnitude without compromising astrometric accuracy by enabling non-sidereal tracking on the target. This will help the NEO follow-up community cope with the accelerated discovery rates and improved sensitivity of the next-generation NEO surveys. Astreaks has been made available to the community under an open-source license.

The low surface thermal inertia of the rapidly rotating near-Earth asteroid 2016 GE1

Context. Asteroids smaller than about 100 m in diameter are observed to rotate very fast, with periods often much shorter than the critical spin limit of 2.2 h. Some of these super-fast rotators can also achieve a very large semimajor axis drift induced by the Yarkovsky effect, which, in turn, is determined by internal and surface physical properties. Aims. We consider here a small super-fast-rotating near-Earth asteroid, designated as 2016 GE1. This object rotates in just about 34 s, and a large Yarkovsky effect has been determined from astrometry. By using these results, we aim to constrain the thermal inertia of the surface of this extreme object. Methods. We used a recently developed statistical method to determine the thermal properties of near-Earth asteroids. The method is based on the comparison between the observed and the modeled Yarkovsky effect, and the thermal conductivity (inertia) is determined via a Monte Carlo approach. Parameters of the Yarkovsky effect model are fixed if their uncertainty is negligible, modeled with a Gaussian distribution of the errors if they are measured, or deduced from general properties of the population of near-Earth asteroids when they are unknown. Results. Using a well-established orbit determination procedure, we determined the Yarkovsky effect on 2016 GE1 and confirm a significant semimajor axis drift rate. Using a statistical method, we show that this semimajor axis drift rate can only be explained by low thermal inertia values below 100 J m−2 K−1 s−1/2. We benchmarked our statistical method using the well-characterized asteroid Bennu and find that only knowing the semimajor axis drift rate and the rotation period is generally insufficient for determining the thermal inertia. However, when the statistical method is applied to super-fast rotators, we find that the measured Yarkovsky effect can be achieved only for very low values of thermal inertia: namely, 90% of the probability density function of the model outcomes is contained at values smaller than 100 J m−2 K−1 s−1/2. Conclusions. We propose two possible interpretations for the extremely low thermal inertia of 2016 GE1: a high porosity or a cracked surface, or a thin layer of fine regolith on the surface. Though both possibilities seem somewhat unexpected, this opens up the possibility of a subclass of low-inertia, super-fast-rotating asteroids.

(433) Eros and (25143) Itokawa surface properties from reflectance spectra

Context. Our knowledge of near-Earth asteroid (NEA) composition is important for planetary research, planetary defence, and future in-space resource utilisation. Upcoming space missions, for example, Hera, M-ARGO, or missions to the asteroid (99942) Apophis, will provide us with surface-resolved NEA reflectance spectra. Neural networks are useful tools for analysing reflectance spectra and determining material composition with high precision and low processing time. Aims. We applied neural-network models on disk-resolved spectra of the Eros and Itokawa asteroids observed by the NEAR Shoemaker and Hayabusa spacecraft. With this approach, the mineral variations or intensity of space weathering can be mapped. Methods. We built and tested two types of convolutional neural networks (CNNs). The first one was trained using asteroid reflectance spectra with known taxonomy classes. The other one used silicate reflectance spectra with assigned mineral abundances and compositions. Results. The reliability of the classification model depends on the resolution of reflectance spectra. Typical F1 score and Cohen's κC values decrease from about 0.90 for high-resolution spectra to about 0.70 for low-resolution spectra. The predicted silicate composition does not strongly depend on spectrum resolution and coverage of the 2-µm band of pyroxene. The typical root mean square error is between 6 and 10 percentage points. For the Eros and Itokawa asteroids, the predicted taxonomy classes favour the S-type and the predicted surface compositions are homogeneous and correspond to the composition of L/LL and LL ordinary chondrites, respectively. On the Itokawa surface, the model identified fresh spots that were connected with craters or coarse-grain areas. Conclusions. The neural network models trained with measured spectra of asteroids and silicate samples are suitable for deriving surface silicate mineralogy with a reasonable level of accuracy. The predicted surface mineralogy is comparable to the mineralogy of returned samples measured in the laboratory. Moreover, the taxonomical predictions can point out locations of fresher areas.

Post-flight Evaluation of Lidar-based Digital Terrain Models for OSIRIS-REx Navigation at Bennu

The Origins, Spectral Interpretation, Resource Identification, and Security–Regolith Explorer (OSIRIS-REx) spacecraft spent more than 2 yr characterizing near-Earth asteroid (101955) Bennu. The OSIRIS-REx Laser Altimeter (OLA) was responsible for producing the most accurate reconstruction of the asteroid’s surface—down to a global resolution of around 5 cm with a data precision of ±1.25 cm. However, the best-quality global OLA digital terrain model (DTM), version 21 (v21), was not available for navigation during proximity operations, nor was the utility of this model evaluated for processing images and altimeter data for navigation. The focus of this paper is the post-flight assessment of the final OLA v21 DTM, its performance for navigation-related analysis, and estimates of corrections needed for the DTM and measurement models. We created 15 cm resolution maplets for processing optical navigation (OpNav) data, and 5 cm resolution DTMs for processing altimeter data, to estimate a combined spacecraft trajectory over five phases of the mission. Our estimated corrections to the OLA instrument model produce altimeter data residuals with a precision of 7.12 cm (1σ; one standard deviation from the mean). The OpNav maplets produce image residuals at 0.2 px (1σ) and estimated landmark locations accurate to ±6 cm, outperforming DTM navigation-related performance requirements. Finally, our estimate of the global DTM scale is more precise and within 1.1σ of previously reported values. We find that a slight discrepancy persists between the image and altimeter data, with image data suggesting that the DTM is too small by 0.049%, but nevertheless is exceptional for navigation.

Determination of the Motion Parameters of Near-Earth Objects from Position Measurements Performed at the Terskol Observatory

The paper presents a method for processing positional observations of near-Earth objects using a numerical model of satellite motion developed at the Research Institute of Applied Mathematics and Mechanics of Tomsk State University (NII PMM TSU). The root-mean-square error of orbit improvement without rejection of observations for such objects does not exceed 0.3″ over a seven-day time interval. The results of the presentation of observations for the next occurrence of the object are obtained, which makes it possible to find the object in a time interval of five months. The orbit has been refined in the joint processing of measurements on several occurrences of the object over a six-month time interval. All results were obtained from observations made on the equipment of the Terskol Observatory Shared Use Center.

Targets selection and mission optimization of kinetic impact deflection test mission for small size asteroids

Near-Earth Asteroids (NEAs) impact poses a major potential threat to life on Earth, and kinetic impact is currently the most mature and feasible means of asteroid defense. The deflection effect of kinetic impact (KI) is closely related to the asteroid orbit, structure, material composition, mechanical properties, impact velocity, and other factors. To ensure the success of an asteroid defense mission, it is crucial to conduct in-orbit test missions and gain a thorough understanding of momentum transfer and orbital deflection principles. The Double Asteroid Redirection Test (DART) Mission has been launched and successfully impacted the Dimorphos whose diameter is 160 m. However, missions specifically targeting near-Earth asteroids with diameters ranging from 20 m to 90 m, which are more abundant but fainter and pose greater challenges in terms of navigation and guidance accuracy, have not been executed. For in-orbit demonstration and performance evaluation of kinetic impact asteroid deflection missions, the selection criteria for candidate asteroids were first established considering the size, orbit distribution, orbit uncertainty, characteristic information, and optical observability. 20 near-Earth asteroids were selected as primary candidate asteroids from the 28,946 cataloged near-Earth asteroids. Then, according to the mission cost and the way to evaluate the deflection distance, two Kinetic Impact in-orbit Demonstration (KID) mission scenarios were designed. A kinetic impact test mission optimization model was developed, integrating global and local optimization algorithms, while considering constraints like launch vehicle, launch site, and observability during and after impact. The model utilized a high-precision orbital dynamics model of the solar system to assess the deflection effect on the asteroid. We further reduced the candidate asteroids to 7 and ranked them in each mission scenario. Additionally, disruption conditions of the asteroids were examined, and mission parameters were re-optimized to ensure deflection without disruption. Accounting for factors such as the momentum enhancement factor, the impact probability between the asteroid and Earth was calculated for a 200-year period following the impact, thus evaluating the risk of an asteroid colliding with Earth after the KID mission implementation. The research can provide references for the target selection and kinetic impact test mission options for 20–90 m asteroids.

The Formation of a Rubble Pile Asteroid: Insights from the Asteroid Ryugu

The Hayabusa2 mission returned primitive samples from the C-type asteroid Ryugu to Earth. The C-type asteroids hold clues to the origin of Earth’s water and the building blocks of life. The rubble pile structure of C-type asteroids is a crucial physical feature relating to their origin and evolution. A rubble pile asteroid is hypothesized to be bound primarily by self-gravity with a significant void space among irregularly shaped materials after catastrophic impacts between larger asteroids. However, the geological observations from Hayabusa2 and the analyses of the returned sample from Ryugu revealed that the high microporosity was common to various &gt;10 m- to mm-sized materials of Ryugu, which suggests that the asteroid Ryugu is not just a loosely bound agglomeration of massive rocky debris from shattered asteroids. For a better understanding of the origin and evolution of the rubble pile asteroid, the current most accepted hypothesis should be verified by observations and laboratory analyses and improved upon based on this information. Here, the previous models are examined using Hayabusa2’s geological observations of the asteroid and the analytical data from the samples returned from Ryugu’s surface and subsurface material. Incorporating the new findings, a hypothesis for the evolution of the rubble pile asteroid Ryugu from a cometary nucleus through sublimation and subsequent dynamic resurfacing is proposed. The proposed hypothesis is applicable to other rubble-pile asteroids and would provide perspectives for near-Earth objects in general.

The Lagrange Sunshade: Its Effectiveness in Combating Global Warming and Its Application to Earth Defense from Asteroid Impacts, Beaming Solar Energy for Terrestrial Use, Propelling Interstellar Migration by Laser-Photon Sails and Its Technosigniature

One suggested method to partially mitigate the effects of global warming is the construction of a ~2,000 km dimension sunshade at or near the Sun-Earth Lagrange-1 (L1) Point. Opaque and transparent sunshades have been suggested for this application. Mass estimates are presented for both as well as a discussion of station-keeping issues. If constructed, such a megastructure would have additional applications. These include beaming energy to divert or destroy Earth-threatening Near Earth Asteroids (NEAS), space-based solar-energy production for terrestrial use, and energy beaming to accelerate laser-photon propelled starships engaged in interstellar migrations. Global warming may be a filter that an emerging galactic civilization might have to overcome. As such, technosignatures of extra solar star-planet Lagrange sunshades might be detectable by extremely large telescopes. Larger Lagrange sunshades might also be constructed by a civilization inhabiting a planet circling an aging star since stellar luminosity increases with star age. Keywords: Lagrange Sunshade, Earth Defence, Space-Based Solar Energy, Interstellar Migration, Technosigniatures

Necessary condition for temporary asteroid capture

Abstract Asteroid capture holds great significance in understanding the origins of asteroids, the source of life, and the exploration of planetary mineral resources. To ensure the success of a mission aimed at capturing asteroids, it is crucial to choose asteroids that can be naturally captured by Earth. This article focuses on the orbital characteristics of temporarily captured asteroids. Through a statistical simulation of asteroid motion and an analytical derivation of the Jacobian integral, the necessary conditions for the temporary capture of asteroids by Earth are calculated. The analysis results show an approximately linear relationship between the orbit elements of temporarily captured asteroids. This condition is used to screen the currently observed near-Earth asteroids and has identified asteroids such as 2006 RH120 and 2020 CD3, which have been temporarily captured by Earth. These findings provide important suggestions for future asteroid capture missions and target selection.

The Hazardous km-sized NEOs of the Next Thousands of Years

The catalog of km-sized near-Earth objects (NEOs) is nearly complete. Typical impact monitoring analyses search for possible impacts over the next 100 yr and none of the km-sized objects represent an impact threat over that time interval. Assessing the impact risk over longer timescales is a challenge since orbital uncertainties grow. To overcome this limitation we analyze the evolution of the minimum orbit intersection distance (MOID), which bounds the closest possible encounters between the asteroid and the Earth. The evolution of the MOID highlights NEOs that are in the vicinity of the Earth for longer periods of time, and we propose a method to estimate the probability of a deep Earth encounter during these periods. This metric is used to rank the km-sized catalog in terms of their long-term impact hazard to identify targets of potential interest for additional observation and exploration.

Preliminary design of the Hayabusa2 extended mission to the fast-rotating asteroid 1998 KY26

The near-Earth asteroid 1998 KY26 is a rendezvous target of the Hayabusa2 extended mission, with a diameter as small as 20–40m and a spin period as short as 10.7min. This research aims to develop a plan for Hayabusa2 operations around this particular asteroid constrained by the remaining spacecraft resources. The main part of this paper begins with the characterization of the orbital and surface dynamics about 1998 KY26. The analysis demonstrates that the orbital motion of the spacecraft in the microgravity environment is dominated by solar radiation pressure, while the centrifugal force due to the high spin rate plays a prominent role at the surface. The dynamical environment significantly differs from that of the original target Ryugu, for which Hayabusa2 was specifically designed, posing technical challenges in close-proximity operations. In particular, this article highlights the feasibility of two primary operations: hovering for station-keeping and controlled descent for close-up observations. The discussion is further extended to more advanced operations, such as those using the projectile and target marker aboard the spacecraft. Our research pushes the envelope to explore one of the smallest members of the Solar System.

Measuring the Orbit Drift of Near-Earth Asteroids by the Yarkovsky Effect

The Yarkovsky effect causes the semimajor axis drift of near-Earth asteroids. The drift can be detected by a precise orbit determination process. Using the proposed algorithm, 2233 out of 27,078 near-Earth asteroids are chosen as the initial candidates. Out of these initial candidates, 769 have a measurable Yarkovsky effect with a signal-to-noise ratio (S/N) larger than 1, and 166 have a measurable Yarkovsky effect with an S/N larger than 3. The ratio between retrograde and prograde near-Earth asteroids is plotted with respect to their size. An average ratio of 2 is found for asteroids with an absolute magnitude between 14 and 21. The measurement work is carried out based on orbit determination software developed by the authors that considers a high-precision dynamical model.