In this work, we investigate the size, thermal inertia, surface roughness and geometric albedo of 10 Vesta family asteroids by using the Advanced Thermophysical Model (ATPM), based on the thermal infrared data acquired by mainly NASA's Wide-field Infrared Survey Explorer (WISE). Here we show that the average thermal inertia and geometric albedo of the investigated Vesta family members are 42 $\rm J m^{-2} s^{-1/2} K^{-1}$ and 0.314, respectively, where the derived effective diameters are less than 10 km. Moreover, the family members have a relatively low roughness fraction on their surfaces. The similarity in thermal inertia and geometric albedo among the V-type Vesta family member may reveal their close connection in the origin and evolution. As the fragments of the cratering event of Vesta, the family members may have undergone similar evolution process, thereby leading to very close thermal properties. Finally, we estimate their regolith grain sizes with different volume filling factors.
The Near-Earth Object Wide-Field Infrared Survey Explorer (NEOWISE) mission continues to detect, track, and characterize minor planets. We present diameters and albedos calculated from observations taken during the second year since the spacecraft was reactivated in late 2013. These include 207 near-Earth asteroids and 8,885 other asteroids. $84\%$ of the near-Earth asteroids did not have previously measured diameters and albedos by the NEOWISE mission. Comparison of sizes and albedos calculated from NEOWISE measurements with those measured by occultations, spacecraft, and radar-derived shapes…
The Near-Earth Object Wide-field Infrared Survey Explorer (NEOWISE) reactivation mission has completed its third year of surveying the sky in the thermal infrared for near-Earth asteroids and comets. NEOWISE collects simultaneous observations at 3.4 um and 4.6 um of solar system objects passing through its field of regard. These data allow for the determination of total thermal emission from bodies in the inner solar system, and thus the sizes of these objects. In this paper we present thermal model fits of asteroid diameters for 170 NEOs and 6110 MBAs detected during the third year of the sur…
We present diameters and albedos computed for the near-Earth and Main Belt asteroids observed by the Near-Earth Object Wide-field Infrared Survey Explorer (NEOWISE) spacecraft during the sixth and seventh years of its Reactivation mission. These diameters and albedos are calculated from fitting thermal models to NEOWISE observations of $199$ NEOs and $5851$ MBAs detected during the sixth year of the survey, and $175$ NEOs and $5861$ MBAs from the seventh year. Comparisons of the near-Earth object diameters derived from Reactivation data with those derived from the WISE cryogenic mission data s…
The Near-Earth Object Wide-field Infrared Survey Explorer (NEOWISE) spacecraft has been conducting a two-band thermal infrared survey to detect and characterize asteroids and comets since its reactivation in Dec 2013. Using the observations collected during the fourth and fifth years of the survey, our automated pipeline detected candidate moving objects which were verified and reported to the Minor Planet Center. Using these detections, we perform thermal modeling of each object from the near-Earth object and Main Belt asteroid populations to constrain their sizes. We present thermal model fi…
Context. Mars-crossing asteroids (MCs) are a dynamically unstable group between the main belt and the near-Earth populations. Characterising the physical properties of a large sample of MCs can help to understand the original sources of many near-Earth asteroids, some of which may produce meteorites on Earth. Aims. Our aim is to provide diameters and albedos of MCs with available WISE/NEOWISE data. Methods. We used the near-Earth asteroid thermal model to find the best-fitting values of equivalent diameter and, whenever possible, the infrared beaming parameter. With the diameter and tabulated …
Context. Over the past decades, several interplanetary missions have studied small bodies in situ, leading to major advances in our understanding of their geological and geophysical properties. These missions, however, have had a limited number of targets. Among them, the NASA Dawn mission has characterised in detail the topography and albedo variegation across the surface of asteroid (4) Vesta down to a spatial resolution of approximately 20 m/pixel scale. Aims. Here our aim was to determine how much topographic and albedo information can be retrieved from the ground with VLT/SPHERE in the ca…
Thermophysical models allow for improved constraints on the physical and thermal surface properties of asteroids beyond what can be inferred from more simple thermal modeling, provided a sufficient number of observations is available. We present thermophysical modeling results of observations from the NEOWISE mission for two near-Earth asteroids which are the targets of the DESTINY+ flyby mission: (3200) Phaethon and (155140) 2005 UD. Our model assumes a rotating, cratered, spherical surface, and employs a Monte Carlo Markov Chain to explore the multi-dimensional parameter space of the fit. We…
We show that a number of claims made in Myhrvold (2018) (hereafter M2018b) regarding the WISE data and thermal modeling of asteroids are incorrect. That paper provides thermal fit parameter outputs for only two of the about 150,000 object dataset and does not make a direct comparison to asteroids with diameters measured by other means to assess the quality of that work's thermal model. We are unable to reproduce the results for the two objects for which M2018b published its own thermal fit outputs, including diameter, albedo, beaming, and infrared albedo. In particular, the infrared albedos pu…
The Visible InfraRed (VIR) mapping spectrometer onboard Dawn mission has obtained the spatial distribution of the spectral reflectance of Vesta in the wavelength ranges between 0.25-1.07 micrometers and 0.95-5.1 micrometers. A photometric correction allows to characterize the intrinsic variability of the surface albedo by removing the dependance of the reflectance from the observing geometry. In this work, we present the photometric correction obtained for observations from the Survey, HAMO and HAMO 2 mission phases at Vesta in the whole spectral range investigated by VIR, as well as the surfa…
Themis family is one of the largest and oldest asteroid populations in the main-belt. Water-ice may widely exist on the parent body (24) Themis. In this work, we employ the Advanced Thermophysical Model as well as mid-infrared measurements from NASA's Wide-Field Infrared Survey Explorer to explore thermal parameters of 20 Themis family members. Here we show that the average thermal inertia and geometric albedo are ~$39.5\pm26.0 ~\rm J m^{-2} s^{-1/2} K^{-1}$ and $0.067\pm0.018$, respectively. The family members have a relatively moderate roughness fraction on their surfaces. We find that the r…
Thermal Model Calibration for Minor Planets Observed with WISE/NEOWISE
借助广角红外巡天探测器（WISE; Wright et al. 2010），我们已经观测到超过157，000颗小行星（Mainzer et al. 2011）。其中包括一些近地天体、主带小行星和不规则卫星，它们通过雷达、掩星和现场成像具有良好的物理特性。我们已经使用这些对象来验证使用WISE测量的热模型的模型，以及Wright等人（2010）中导出的四个WISE带通作为有效温度的函数的颜色校正。我们已经使用了50个物体的直径测量雷达，掩星或原位成像的特点隐含的系统误差使用WISE数据与面球面NEATM模型计算直径和dos。通过使用之前测量的直径和H星等与球形NEATM模型，我们计算预测通量后，应用Wright等人（2010）在WISE波段给出的颜色校正，并将它们与测量的星等进行比较。我们发现最小的系统通量误差为5- 10%，产生最小的相对直径和最小的误差分别为~10%和~ 20%。计算了这些天体的可见光反射率，并与3.4和4.6微米的可见光反射率进行了比较，后者包含了大多数小行星反射的阳光和热辐射的混合物。我们推导出太阳下温度和有效温度之间的线性关系，这使得Wright等人（2010）中给出的颜色校正可以通过仅计算太阳下温度而不是小面的热模型来用于小行星。在本文中推导出的热模型并不打算取代以前的测量使用雷达或航天器成像，而是，我们用它们来描述的错误，应该预期计算直径和WISE小行星…
Quantifying the accuracy with which physical properties of asteroids can be determined from thermal modeling is critical to measuring the impact of infrared data on our understanding of asteroids. Previous work (Mainzer et al. 2011b) has used independently-derived diameters (from asteroid radar, occultations, and spacecraft visits) to test the accuracy of the NEOWISE diameter determinations. Here, we present a new and different method for bounding the actual NEOWISE diameter errors in the Main Belt based on our knowledge of the albedos of asteroid families. We show the 1 sigma relative diamete…
We analyzed 82,548 carefully curated observations of 4420 asteroids with Wide-field Infrared Survey Explorer (WISE) four-band data to produce estimates of diameters and infrared emissivities. We also used these diameter values in conjunction with absolute visual magnitudes to infer estimates of visible-band geometric albedos. We provide solutions to 131 asteroids not analyzed by the NEOWISE team and to 1778 asteroids not analyzed with four-band data by the NEOWISE team. Our process differs from the NEOWISE analysis in that it uses an accurate solar flux, integrates the flux with actual bandpas…
Delivery of Dark Material to Vesta via Carbonaceous Chondritic Impacts
美国宇航局的黎明号航天器对小行星（4）灶神星的观测显示，它的表面是我们迄今为止观测到的任何小行星中最高的亮度和颜色变化。使用黎明分幅相机（FC）0.75微米滤光片图像，在几种地质环境中发现了富含低散射暗物质的地形：与撞击坑有关（在喷出物覆盖层材料中和/或撞击坑壁和边缘上）;通常与地形高点有关的流动状沉积物或射线;以及撞击坑附近的暗点（可能是二次撞击）。这DM可能是一个遗迹的古代火山活动或外源的起源。我们报告说，DM的光谱的大部分是类似的碳质球粒陨石混合的材料土著灶神星。使用高分辨率的七色图像，我们比较了DM的颜色特性（色度，带深）与实验室测量的可能的模拟材料。DM的条带深度和宽度与富碳球粒陨石捕虏体的Howardite Mt.普拉特（PRA）04401。Murchison CM 2碳质球粒陨石和玄武质钙铝榴石Millbillillie的实验室混合物也显示了带深度和对DM的亲合力。DM（1-6体积%）中碳质球粒陨石丰度的建模与豪威陨石一致。我们没有发现大规模的火山活动（暴露的岩脉/火山碎屑瀑布）作为DM的来源的证据。我们使用撞击坑比例律和喷出物再增生的数值模型进行的建模工作表明，在低速（<2公里/秒）碳质撞击物形成约400公里Veneneia盆地期间，该DM在灶神星上的输送和就位。这一发现很重要，因为它强化了长期以来的观点，即原始天体是早期太阳系中碳和可能挥发物的来源。
Automated asteroid detection routines set requirements on the number of detections, signal-to-noise ratio, and the linearity of the expected motion in order to balance completeness, reliability, and time delay after data acquisition when identifying moving object tracklets. However, when the full-frame data from a survey are archived, they can be searched later for asteroids that were below the initial detection thresholds. We have conducted such a search of the first three years of the reactivated NEOWISE data, looking for near-Earth objects discovered by ground-based surveys that have previo…
Large potentially hazardous asteroids (PHAs) are capable of causing a global catastrophe in the event of a planetary collision. Thus, rapid assessment of such an object's physical characteristics is crucial for determining its potential risk scale. We treated the near-Earth asteroid (99942) Apophis as a newly discovered object during its 2020-2021 close-approach as part of a mock planetary defense exercise. The object was detected by the Near-Earth Object Wide-field Infrared Survey Explorer (NEOWISE), and data collected by the two active bands (3.4 $μ$m and 4.6 $μ$m) were analyzed using therma…
Dawn's framing camera observed boulders on the surface of Vesta when the spacecraft was in its lowest orbit (LAMO). We identified, measured, and mapped boulders in LAMO images, which have a scale of 20 m per pixel. We estimate that our sample is virtually complete down to a boulder size of 4 pixels (80 m). The largest boulder is a 400 m-sized block on the Marcia crater floor. Relatively few boulders reside in a large area of relatively low albedo, surmised to be the carbon-rich ejecta of the Veneneia basin, either because boulders form less easily here or live shorter. By comparing the density…
Basaltic asteroids (V-types) are believed to be fragments of large differentiated bodies. The majority of them are found in the inner part of the asteroid belt, and are current or past members of the Vesta family. Recently, some V-type asteroids have been discovered far from the Vesta family supporting the hypothesis of the presence of multiple basaltic asteroids in the early solar system. The discovery of basaltic asteroids in the outer belt challenged the models of the radial extent and the variability of the temperature distribution in the early solar system. We aim to identify new basaltic…
Thermal infrared observations are the most effective way to measure asteroid diameter and albedo for a large number of near-Earth objects. Major surveys like NEOWISE, NEOSurvey, ExploreNEOs, and NEOLegacy find a small fraction of high albedo objects that do not have clear analogs in the current meteorite population. About 8% of Spitzer-observed near-Earth objects have nominal albedo solutions greater than 0.5. This may be a result of lightcurve variability leading to an incorrect estimate of diameter or inaccurate absolute visual magnitudes. For a sample of 23 high albedo NEOs we do not find t…
This work proposes a thermophysical model for realistic surface layers on airless small bodies (RSTPM), for the use of interpreting their multi-epoch thermal lightcurves (e.g WISE/NEOWISE). RSTPM considers real orbital cycle, rotation cycle, rough surface, temperature dependent thermal parameters, as well as contributions of sunlight reflection to observations, hence being able to produce precise temperature distribution and thermal emission of airless small bodies regarding the variations in orbital time scales. Details of the physics, mathematics and numerical algorithms of RSTPM are present…
Near Earth Objects (NEOs) are small Solar System bodies whose orbits bring them close to the Earth's orbit. We are carrying out a Warm Spitzer Cycle 11 Exploration Science program entitled NEOSurvey --- a fast and efficient flux-limited survey of 597 known NEOs in which we derive diameter and albedo for each target. The vast majority of our targets are too faint to be observed by NEOWISE, though a small sample has been or will be observed by both observatories, which allows for a cross-check of our mutual results. Our primary goal is to create a large and uniform catalog of NEO properties. We …
(704) Interamnia is one of the largest asteroids that locates in the outer main-belt region, which may contain a large amount of water ice underneath its surface. We observe this asteroid using 8.2 m Subaru telescope at mid-infrared wavebands, and utilize thermophysical model for realistic surface layers (RSTPM) to analyze mid-infrared data from Subaru along with those of IRAS, AKARI and WISE/NEOWISE. We optimize the method to convert the WISE magnitude to thermal infrared flux with temperature dependent color corrections, which can provide significant references for main-belt asteroids at a l…
In this work, we investigate the surface thermophysical properties (thermal emissivity, thermal inertia, roughness fraction and geometric albedo) of asteroid (99942) Apophis, using the currently available thermal infrared observations of CanariCam on Gran Telescopio CANARIAS and far-infrared data by PACS of Herschel, on the basis of the Advanced thermophysical model. We show that the thermal emissivity of Apophis should be wavelength dependent from $8.70~μm$ to $160~μm$, and the maximum emissivity may arise around $20~μm$ similar to that of Vesta. Moreover, we further derive the thermal inerti…
We publicly release ATM, a Python package designed to model asteroid flux measurements to estimate an asteroid's size, surface temperature distribution, and emissivity. The full multi-dimensional posterior pdf is found using Markov Chain Monte Carlo. Data files with $\sim$ 2.5 million WISE flux measurements for $\sim$ 150,000 asteroids and additional MPC data are also included with the package, as well as Python Jupyter Notebooks with examples of analysis. The entirety of the analysis presented here, including all the figures, tables, and catalogs, can be easily reproduced with these publicly …
