near-Earth Research Articles

Sample and Statistical Analysis on NEOWISE Variability of ATLASGAL Sources

This study focuses on the analysis of mid-infrared variability in a sample of high-mass young stellar objects (YSOs) associated with the cataloged sources from the APEX Telescope Large Area Survey of the Galaxy (ATLASGAL). The Near-Earth Object Wide-field Infrared Survey Explorer Reactivation Mission (NEOWISE) database was used to explore the long-term mid-infrared variability of these high-mass YSOs at a half-year scale. After matching with NEOWISE photometric measurements, a total of 2230 ATLASGAL sources were selected for the variability analysis, out of which 717 were identified as variables. The derived proportions of variables at different evolutionary stages show that the variability rate of high-mass YSOs is highest during the YSO stage and decreases with evolution toward the H ii region stage, resembling the behavior of low-mass YSOs. The variables can be classified into six types based on their light curves, divided into two categories: secular (linear, sin, sin+linear) and stochastic variables (burst, drop, and irregular). The magnitude–color variations observed in ∼160 secular variables can be mainly divided into “bluer when brighter/redder when dimming” and “redder when brighter/bluer when dimming,” likely originating from changes in accretion rate or the effect of extinction due to obscuration. Moreover, several episodic accretion candidates were selected for further observational studies.

A deep analysis for New Horizons’ KBO search images

Abstract Observation datasets acquired by the Hyper Suprime-Cam (HSC) on the Subaru Telescope for NASA’s New Horizons mission target search were analyzed through a method devised by JAXA. The method makes use of Field Programmable Gate arrays and was originally used to detect fast-moving objects such as space debris or near-Earth asteroids. Here we present an application of the method to detect slow-moving Kuiper Belt Objects (KBOs) in the New Horizons target search observations. A cadence that takes continuous images of one HSC field of view for half a night fits the method well. The observations for the New Horizons Kuiper Belt Extended Mission (NH/KEM) using HSC began in 2020 May, and are ongoing. Here we show our result of the analysis of the dataset acquired from 2020 May through 2021 June that have already passed the proprietary period and are open to the public. We detected 84 KBO candidates in the 2020 June and 2021 June datasets, when the observation field was close to opposition.

ICC-BiFormer: A Deep-Learning Model for Near-Earth Asteroid Detection via Image Compression and Local Feature Extraction

Detecting near-Earth asteroids (NEAs) is crucial for research in solar system and planetary science. In recent year, deep-learning methods have almost dominated the task. Since NEAs represent only one-thousandth of the pixels in images, we proposed an ICC-BiFormer model that includes an image compression and contrast enhancement block and a BiFormer model to capture local features in input images, which is different from previous models based on Convolutional Neural Network (CNN). Furthermore, we utilize a larger input size of the model, which corresponds to the side length of the input image matrix, and design a cropping algorithm to prevent NEAs from being truncated and better divide NEAs and satellites. We apply our ICC-BiFormer model into a dataset of approximately 20,000 streak and 40,000 non-streak images to train a binary classification model. The ICC-BiFormer achieves 99.88% accuracy, which is superior to existing models. Focusing on local features has been proven effective in detecting NEAs.

Optical observations of the potentially hazardous asteroid (4660) Nereus at opposition 2021

On 11 December 2021 at 11 UTC, the near-Earth asteroid (4660) Nereus passed the Earth at a distance of 0.0263 au, reaching about 13th magnitude that made it an excellent target for ground-based observations. We observed the asteroid photometrically from 11 October 2021, when it was visible at V = 17.7 mag, until 16 February 2022 (at V = 18.0 mag), and spectroscopically on 10 December 2021 (V ∼ 13.1 mag).Lightcurve analysis of (4660) Nereus gave a rotational period of 15.184245±0.000015 h with amplitude of 0.796 ± 0.052 mag. Fitting the magnitude-phase curve with the standard HG, HG1G2, HG12 functions yielded the following values: HR = 18.68−0.13+0.07 mag, G = 0.30−0.11+0.05; HR = 18.64−0.84+0.42 mag, G1 = 0.21−0.11+0.05, G2 = 0.46−0.23+0.22; HR = 18.61−0.07+0.13 mag, G12 = 0.18−0.18+0.18. The color indices of the asteroid at phase angle of 72.9° were found to be as follows: (B−V) = 0.688 ± 0.084, (B−R) = 1.046 ± 0.073, (V−R) = 0.358 ± 0.047, (V−I) = 0.718 ± 0.050. Its equivalent diameter was estimated as 0.34−0.10+0.07 km. These values, as well as the computed values of G1 and G2 coefficients, indicate that (4660) Nereus belongs to E-class asteroids. The same conclusion was made based on the spectra obtained.

Orbit determination of asteroid (469219) Kamo‘oalewa using a combination of historical and new observations

ABSTRACT The orbit solution of near-Earth asteroids heavily relies on ground-based optical observations. The orbit uncertainty is limited by the insufficient observation quantity and quality. The Chinese Tianwen-2 mission targets a near-Earth asteroid (469219) Kamo‘oalewa and a main-belt comet, 311P/PANSTARRS. To accurately determine the orbit of Kamo‘oalewa, more optical observations are needed. Autonomous observation experiments focusing on Kamo‘oalewa were carried out using the 2.16-m telescope at the Xinglong Observatory of the National Astronomical Observatory of China. We found that this telescope could observe near-Earth asteroids as faint as a magnitude of 22.8. Based on the stacking method and trailed star extraction algorithm, 14 optical observations were obtained from 2022 to 2024. The orbit for Kamo‘oalewa was determined by combining our observations with historical observations between 2004 and 2024. The inclusion of our observations results in improved orbital uncertainties of Kamo‘oalewa by 18.67, 7.93, and 11.12 km (1σ) in the X, Y, and Z directions, respectively. Furthermore, by combining all existing and simulated observations, the uncertainty of the orbital determination of Kamo‘oalewa was analysed. When using an additional 180 group observations from 3 Chinese observatories over 2 yr, the orbital uncertainties of Kamo‘oalewa in the 3 directions could be reduced to 30 km (1σ).

Gaia Data Release 3: Distribution of Spectral Groups of Near-Earth Asteroids

Gaia Data Release 3: Distribution of Spectral Groups of Near-Earth Asteroids

MARTIANS (MARs2020, TIANwen and So on) would see more potentially hazardous asteroids than Earthlings

Abstract Potentially Hazardous Asteroids (PHAs) are a special subset of Near-Earth Objects (NEOs) that can come close to the Earth and are large enough to cause significant damage in the event of an impact. Observations and researches of Earth-PHAs have been underway for decades. Here, we extend the concept of PHAs to Mars and study the feasibility of detecting Mars-PHAs in the near future. We focus on PHAs that truly undergo close approaches with a planet (dubbed CAPHAs) and aim to compare the actual quantities of Earth-CAPHAs and Mars-CAPHAs by conducting numerical simulations incorporating the Yarkovsky effect, based on observed data of the main asteroid belt. The estimated number of Earth-CAPHAs and Mars-CAPHAs are 4675 and 16910, respectively. The occurrence frequency of Mars-CAPHAs is about 52 per year, which is 2.6 times that of Earth-CAPHAs, indicating significant potential for future Mars-based observations. Furthermore, a few Mars-CAPHAs are predicted to be observable even from Earth around the time of next Mars opposition in 2025.

Optimal combined impulsive/low-thrust trajectories for asteroid deflection via kinetic impact

This work considers the trajectory optimization of a kinetic impactor spacecraft, which is sent to collide with a threatening near-Earth asteroid. It is assumed that Earth departure is done impulsively, by the upper stage of a launch vehicle, and is then followed by low-thrust electric propulsion until impact. For a given spacecraft, all of the important decision parameters, such as the date of departure, the direction of the hyperbolic departure, the thrust program, i.e. the history of the low-thrust pointing angles, and the date of impact are all chosen by the optimizer to maximize the perigee radius of the asteroid at its closest approach. Normally a trajectory optimization problem of this type would need to be described by many hundreds of decision parameters, e.g. if formulated to be solved by an optimization package (such as GPOPS) using nonlinear programming. We show that a successful and accurate optimization of the mission is possible using the heuristic method, particle swarm, and only 16 decision parameters, and present results for the deflection of 99942 Apophis at its 2029 close approach.

Recent collisional history of (65803) Didymos

The Double Asteroid Redirection Test (DART, NASA) spacecraft revealed that the primary of the (65803) Didymos near-Earth asteroid (NEA) binary system is not exactly the expected spinning top shape observed for other km-size asteroids. Ground based radar observations predicted that such shape was compatible with the uncertainty along the direction of the asteroid spin axis. Indeed, Didymos shows crater and landslide features, and evidence for boulder motion at low equatorial latitudes. Altogether, the primary seems to have undergone sudden structural failure in its recent history, which may even result in the formation of the secondary. The high eccentricity of Didymos sets its aphelion distance inside the inner main belt, where it spends more than 1/3 of its orbital period and it may undergo many more collisions than in the NEA region. In this work, we investigate the collisional environment of this asteroid and estimate the probability of collision with multi-size potential impactors. We analyze the possibility that such impacts produced the surface features observed on Didymos by comparing collisional intervals with estimated times for surface destabilization by the Yarkovsky-O’Keefe-Radzievskii-Paddack (YORP) effect. We find that collisional effects dominate over potential local or global deformation due to YORP spin up.

Collective action problems in planetary defense

In recent years, growing awareness of potential threats posed by near-Earth objects (NEOs) has led to increased interest in developing and implementing planetary defense measures. International cooperation and public support are crucial to ensuring the long-term success of planetary defense initiatives. However, a number of economic, political, legal, and social issues stand in the way of effective large-scale cooperation in pursuing planetary defense. This article examines the major challenges to international cooperation in planetary defense. The article begins by considering the major types of collective action problems facing international collaboration toward planetary defense. The article then examines the way in which adjacent space-related aspects of international affairs influence the arena of planetary defense. The article then analyzes the legal aspects of these cooperation problems, focusing on sources of perceived uncertainty that interfere with effective development of norms for cooperation. The article then proposes various possible strategies for avoiding cooperation problems and increasing collective buy-in. Noteworthy examples include the use of treaties as pre-commitment devices (which parties agree to undertake in order to limit their future options and commit themselves to pre-established lines of conduct) and amendments to existing legal frameworks to decrease perceived uncertainty and promote objective standards of cooperation. The article concludes by reflecting on the importance of promoting a widespread cultural perspective that emphasizes the pursuit of collective planetary welfare over competing national interests.

The Sensitivity of NEO Surveyor to Low-perihelion Asteroids

Asteroids with low orbital perihelion distances experience extreme heating from the Sun that can modify their surfaces and trigger nontypical activity mechanisms. These objects are generally difficult to observe from ground-based telescopes due to their frequent proximity to the Sun. The Near-Earth Object (NEO) Surveyor mission, however, will regularly survey down to solar elongations of 45° and is well suited for the detection and characterization of low-perihelion asteroids. Here, we use the survey simulation software tools developed for mission verification to explore the expected sensitivity of NEO Surveyor to these objects. We find that NEO Surveyor is expected to be >90% complete for near-Sun objects larger than D ∼ 300 m. Additionally, if the asteroid (3200) Phaethon underwent a disruption event in the past to form the Geminid meteor stream, Surveyor will be >90% complete to any fragments larger than D ∼ 200 m. For probable disruption models, NEO Surveyor would be expected to detect dozens of objects on Phaethon-like orbits, compared to a predicted background population of only a handful of asteroids, setting strong constraints on the likelihood of this scenario.

Radar and Optical Observations and Physical Modeling of Binary Near-Earth Asteroid 2018 EB

We report radar, photometric, and visible-wavelength spectrophotometry observations of NEA 2018 EB obtained in 2018. The radar campaign started at Goldstone (8560 MHz, 3.5 cm) on April 7, and it was followed by more extensive observations from October 5 to 9 by both Arecibo (2380 MHz, 12.6 cm) and Goldstone. 2018 EB was observed optically on April 5, 8, and 9 and again on October 18. Spectrophotometry was obtained on October 19 with the SOAR telescope, and the data suggest that 2018 EB is an Xk-class object. The echo power spectra and delay-Doppler radar images revealed that 2018 EB is a binary system. Radar images constrained the satellite's diameter to 0.15−0.05+0.02 km, but the data were not sufficient for shape modeling. Shape modeling of lightcurves and radar data yielded an oblate primary with an effective diameter D = 0.30 ± 0.04 km and a sidereal rotation period of 4.3−0.5+0.6 hr. Measurements of delay-Doppler separations between the centers of mass of the primary and the satellite, along with the timing of a radar eclipse observed on October 9, resulted in an orbit fit for the satellite with a semimajor axis of 0.50−0.01+0.04 km, an eccentricity of 0.15 ± 0.04, a period of 16.85−0.26+0.33 hr, and an orbit pole constrained to the ecliptic longitudes and latitudes of λ=93−43°+27° and β=48−18°+7° . The system mass was estimated to be 2.03−0.08+0.52×1010 kg, which yielded a bulk density of 1.4−0.5+0.6 g cm−3. Our analysis suggests that 2018 EB has a low optical albedo of p V = 0.028 ± 0.016 and a relatively high radar albedo of η OC = 0.29 ± 0.11 at Arecibo and η = 0.22 ± 0.10 at Goldstone.

High Specific-Impulse Electrospray Explorer Trajectory Guidance and Control Air Bearing Demonstration

As small satellite-mission concepts that require travel farther from their traditional domain of low-Earth orbit are being considered, there is a growing need to develop small-scale propulsion systems that can provide the necessary net impulse to enable deep-space operation. The High Specific-Impulse Electrospray Explorer for Deep-Space (HiSPEED) project is an example concept considered for this paper, as it would be a small satellite that uses electrospray thrusters to navigate along a low-thrust spiral trajectory from Earth to a near-Earth asteroid. The NASA Jet Propulsion Laboratory Small Satellite Dynamics Testbed operates simulation and air- bearing testing environments. This paper focuses on its planar air-bearing platform used to create a nearly frictionless environment in three degrees of freedom: two translational and one rotational. The platform maneuvers using eight compressed air thrusters controlled by an onboard single-board computer using position feedback from a motion-capture system. This paper discusses the design, development, and testing of a closed-loop controller for this platform that enables trajectory following with position error less than 4 cm. The paper presents data from tests representative of HiSPEED spiral escape trajectories and operations in proximity to an asteroid, along with implications for HiSPEED and similar concepts.

Long-term Monitoring of Didymos with the LCOGT Network and MRO after the DART Impact

The world’s first planetary defense test mission was carried out in late 2022 by NASA’s Double Asteroid Redirection Test (DART) mission. The main DART spacecraft, which was accompanied by the ASI-provided LICIACube cubesat, intentionally impacted Dimorphos, the smaller secondary of the near-Earth object binary system (65803) Didymos, on 2022 September 26. The impact released a large amount of ejecta, which, combined with the spacecraft’s momentum, produced the observed 33 ± 1 minute period change that was subsequently observed from ground-based telescopes. The DART mission, in addition to having successfully changed the orbital period of Dimorphos, also activated the asteroid as a result of the impact but under known conditions, unlike other impacts on asteroids. We have conducted long-term monitoring over 5 months following the impact with the Las Cumbres Observatory Global Telescope (LCOGT) network and Magdalena Ridge Observatory (MRO). This was supplemented by almost 3 months of more sparsely sampled data, primarily from educational users of the LCOGT network during the period from 2022 July 5 to 2022 September 25, prior to the impact date of 2022 September 26. Here we report the observations of the Didymos system and DART impact ejecta with the telescopes of the LCOGT network from T+1.93 days to T+151.3 days after impact, and we study the evolving morphology of the ejecta cloud and evolving tail over the entire length of the data set. In addition, we combined these intensive data sets with the earlier sparse observations over the ∼90 days prior to impact to derive a new disk-integrated phase function model using the H, G 1, G 2 parameterization.

NEOMOD 3: The debiased size distribution of Near Earth Objects

Our previous model (NEOMOD2) for the orbital and absolute magnitude distribution of Near Earth Objects (NEOs) was calibrated on the Catalina Sky Survey observations between 2013 and 2022. Here we extend NEOMOD2 to include visible albedo information from the Wide-Field Infrared Survey Explorer. The debiased albedo distribution of NEOs can be approximated by the sum of two Rayleigh distributions with the scale parameters pV,dark≃0.03 and pV,bright≃0.17. We find evidence for smaller NEOs having (on average) higher albedos than larger NEOs; this is likely a consequence of the size-dependent sampling of different main belt sources. These inferences and the absolute magnitude distribution from NEOMOD2 are used to construct the debiased size distribution of NEOs. We estimate 830±60 NEOs with diameters D>1 km and 20,000±2,000 NEOs with D>140 m. The new model, NEOMOD3, is available via the NEOMOD Simulator — an easy-to-operate code that can be used to generate user-defined samples (orbits, sizes and albedos) from the model.

A Multi-Stage Sample Return Architecture for Interplanetary Exploration with Planetary Protection Measures

This study proposes a novel multi-stage sample return architecture for missions to near-Earth objects and other planetary bodies. Our approach prioritizes scientific return while minimizing mission complexity and adhering to planetary protection protocols. Traditional sample return directly to Earth presents logistical challenges and back contamination risks. This architecture proposes intermediary destinations, such as the International Space Station (ISS) or lunar laboratories, for initial sample screening and containment. Following these initial analyses, only demonstrably safe samples would be transferred to Earth for in-depth investigation. This multi-stage approach leverages existing technologies and promotes responsible planetary exploration. The paper concludes with a discussion of the mission's feasibility and its potential impact on future interplanetary sample return endeavors. A schematic of the proposed architecture is included.

Candidate Main-belt Asteroids for Surface Heterogeneity

Large terrestrial bodies in our solar system like the Earth, Mars, Mercury, and the Moon exhibit geologically complex surfaces with compositional heterogeneity. From past studies using large telescopes and spacecraft, it was shown that asteroids with diameters larger than 100 km also show surface heterogeneity at hemispheric scales, while on smaller objects, such features remain to be detected. Here, we investigate candidates for surface heterogeneity in a sample of 130 main-belt asteroids using multiepoch spectroscopic data from the MIT–Hawaii Near-Earth Object Spectroscopic Survey, which has been observing asteroids for about 20 yr using a self-consistent observation technique. Twelve conservative candidates with spectra more than 3σ apart from each other at 2.4 μm and 52 optimistic candidates for surface heterogeneity are detected. These candidates include eight objects already reported as being heterogeneous. Our study suggests that the size boundary between small homogeneous asteroids and larger heterogeneous objects, if it exists, is lower than 100 km. A-type asteroids have a higher proportion of heterogeneous candidates than other asteroids. This may be because olivine, which is the main surface constituent of these objects, reacts more efficiently to space weathering with respect to pyroxene, such that a similar range of surface ages will translate into a wider range of optical-to-near-infrared spectral slopes in the case of A-type bodies.

Developing algorithms to determine an Asteroid’s physical properties and the success of deflection missions

The rate of discovery of near-Earth asteroids currently outpaces our ability to analyze them. Knowledge of an asteroid's physical properties is essential to deflect them. I developed free and open-source algorithms and training modules. These tools utilize images from robotic telescopes, open-source data, and high school-level mathematics to determine asteroids' size, rotation period, and strength. I took observations of the Didymos binary asteroid, and my algorithm determined its size to be 850 ± 0.04 m, with a 2.261 ± 0.018 h rotation period and rubble-pile strength. I measured a decrease in the mutual orbital period after impact by NASA's 2022 DART Mission, confirming successful deflection. My findings matched closely with those obtained by NASA and external sources (Daly et al., 2023; Thomas et al., 2023; Talbert, 2022, October 11; Nakanoet al., 2022) [1,2,3,4]. Every young person and citizen scientist can now be a planetary defender.

Near-earth asteroids classification using NGBoost classifier

Near-Earth asteroids (NEAs) are celestial bodies that orbit within close to Earth, offering valuable insights into the early solar system's formation and posing potential hazards due to impact events. This work presents a comprehensive overview of NEAs, encompassing their historical significance, characteristics, impact hazards, and prospects. The study outlines the NASA Asteroids Classification Dataset and discusses its importance for research on asteroid classification and risk assessment. Furthermore, the methodology section delineates the utilization of the NGBoost classifier for predictive modeling tasks, detailing data collection, preprocessing, model training, evaluation, and result interpretation. Results from the NGBoost classifier demonstrate high accuracy and performance metrics in classifying asteroids, underscoring its efficacy in advancing asteroid classification efforts and informing planetary defense strategies. NEAs pose a potential threat to our planet, and their classification is essential for understanding their properties and predicting their trajectories accurately. In this research, we explore the application of NGBoost, a powerful gradient-boosting framework, for classifying NEAs based on their orbital and physical characteristics. We present a dataset comprising features extracted from known NEAs and non-NEAs and demonstrate the efficacy of NGBoost in accurately distinguishing between these classes. Our results indicate promising performance metrics with 99.22% accuracy, suggesting that NGBoost holds potential as a valuable tool in asteroid classification.

Near-Earth Asteroids Orbit Determination by DRO Space-Based Optical Observations

In response to the problem that ground-based optical monitoring systems cannot monitor near-Earth asteroids which are in the direction too close to the Sun on the celestial sphere, we raise a method that tracks and determines the orbit of asteroids by Distant Retrograde Orbit (DRO) platforms with optical monitoring. Through data filtering by visibility analysis and the initial orbit information of the asteroids provided by Jet Propulsion Laboratory (JPL), the asteroids’ orbits are determined and compared with the reference orbit. Simulation results show that with a measurement accuracy of two arcseconds and an arc length of three years, the orbit determination accuracy of the DRO platform for near-Earth asteroids selected in the simulation example can reach tens of kilometers, especially the asteroids with Atira orbits to an accuracy of fewer than ten kilometers. In conclusion, the near-Earth asteroids monitoring systems based on DRO platforms are capable to provide sufficient monitoring effectiveness which enables precisely tracking of the target asteroids and forecast of their positions.