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At least 1,747 records · Page 97
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NASA NTRS2018

What Hayabusa2 Will Find at Asteroid Ryugu, and What It Will Reveal About the Source of Earth's Water

Water-rich carbonaceous chondrites contain evidence of aqueous alteration in the early solar system. To see this one must look carefully at the meteorites, and see past the later alteration which has generally obscured mineral textures. We suggest that these materials will dominate, be detectable, and be sampled on the surfaces of C-class asteroids, initially by the Hayabusa2 spacecraft. Thus, hydrous samples returned by this mission will help to reveal the source of water on earth.

Zolensky, Michael↗
NASA NTRS2018

Using Dust Shed from Asteroids as Microsamples to Link Remote Measurements with Meteorite Classes

Given the diversity of asteroids, it is impossible to consider returning samples from each one• Dust particles are abundant around asteroids• Primary minerals and organic materials can be measured by in situ dust detectorinstruments• These particles can be used to classify the parent body as an ordinary chondrite,basaltic achondrite, or other class of meteorite• Such instruments could provide direct links to known meteorite groups withoutreturning the samples to terrestrial laboratories

Cohen, B. A.↗
NASA NTRS2016

Microspine Gripping Mechanism for Asteroid Capture

This paper details the development and early testing of a compliant suspension for a microspine gripper device for asteroid capture or zero-gravity percussive drilling. The microspine gripper architecture is reviewed, and a proposed microspine suspension design is presented and discussed. Prototyping methods are discussed, as well as testing methods and results. A path forward is identified from the results of the testing completed thus far. Key findings include: the microspine concept has been established as a valid architecture and the compliant suspension exhibits the desired stiffness characteristics for good gripping behavior. These developments will aid in developing the capability to grasp irregularly shaped boulders in microgravity.

Merriam, Ezekiel G.↗
NASA NTRS2016

Big Science in Small Packages: a Constellation of Cubesats to Search for Near Earth Asteroids

Astronomers for many decades have been searching for Near Earth Asteroids (NEA) that could potentially impact the Earth in the future. Large Synoptic Survey Telescope (LSST), when completed, would be by far the most powerful tool for a ground-based search for NEAs. In space, IR telescopes are undergoing detailed design studies. These facilities are projected to find 90% of potentially hazardous NEAs in about a dozen years. We introduce a different approach to search for these objects by using multiple micro- and nano-spacecraft distributed in orbit around the Sun. Their ability to faint moving objects with small telescopes is based on a new generation of low noise, fast-frame cameras combined with processors that can execute 100’s of gigaflops in a low power space environment.

Shao, Michael↗
NASA NTRS2016

Application of Model-Based Systems Engineering for the Development of the Asteroid Redirect Robotic Mission

Model-Based Systems Engineering (MBSE) can augment existing Systems Engineering (SE) processes to more efficiently deliver enhanced products over the project life cycle. Using a multi-user accessible System Model, MBSE has been successfully deployed for the conceptual and preliminary design development of the Asteroid Redirect Robotic Mission (ARRM). The paper provides an overview and examples of the targeted MBSE deployment for development of the mission operational concept, system description, and functional requirements. The paper also includes description of the challenges and lessons learned.

Sindiy, Oleg V.↗
NASA NTRS2016

Thermochemistry of Strong Air Plasmas for Hypervelocity Earth Entry of Asteroids

The specific heat, enthalpy and free energy of nitrogen and oxygen are calculated for pressures between 1 and 100 bars and temperatures between 10,000 and 100,000 degrees Kelvin. The data are presented in a form suitable for input into computational fluid dynamics computer codes. This range of temperature and pressure are typical of the conditions expected in the bow shock layer of a meteor or small asteroid entering Earth's atmosphere. The extent of double and triple ionization of nitrogen and oxygen atoms under these conditions will be estimated.

Ionization Energy Depression↗
NASA NTRS2020

Revisiting OSIRIS-REx Touch-And-Go (TAG) Performance Given the Realities of Asteroid Bennu

The Origins, Spectral Interpretation, Resource Identification, and Security–Regolith Explorer (OSIRIS-REx) mission is a NASA New Frontiers mission that launched in 2016 and rendezvoused with the near-Earth asteroid (101955) Bennu in late 2018. Upon arrival, the surface of Bennu was found to be much rockier than expected. The original Touch-and-Go (TAG) requirement for sample collection was to deliver the spacecraft to a site with a 25-meter radius; however, the largest hazard-free sites are no larger than 8 meters in radius. To accommodate the dearth of safe sample collection sites, the project reevaluated all aspects of flight system performance pertaining to TAG in order to account for the demonstrated performance of the spacecraft and navigation prediction accuracies. More-over, the project has base lined on board natural feature tracking instead of lidar for providing the on board navigation state update during the TAG sequence. This paper summarizes the improvements in error source estimation, enhancements in on board trajectory correction, and results of recent Monte Carlo simulation to en-able sample collection with the given constraints. TAG delivery and on board navigation performance are presented for the final four candidate TAG sites.

Berry, Kevin↗
NASA NTRS2020

Thermal Evolution and Core Formation on Asteroid 4 Vesta in the Magma Ocean Regime

Geochemical observations of the eucrite and diogenite meteorites, together with observations made by NASA’s Dawn spacecraft while orbiting asteroid 4 Vesta, indicate that Vesta has differentiated to form a crust, mantle, and core. Eucrite and diogenite petrology is best explained by solidification of the crust from a magma ocean constituting 60-70% of Vesta’s silicates [3], or a temperature of ~1550 °C. The abundances of moderately siderophile elements (Ni, Co, Mo, W, and P) in eucrites require that essentially all of the metallic phase in Vesta segregated to form a core prior to eucrite formation and likely reached a temperature of 1450- 1575 °C. These observations provide important constraints on Vesta’s thermal evolution. The high inferred temperature indicates that convective heat transport must have been important during part of Vesta’s thermal evolution. In this study, we model Vesta’s thermal evolution in the magma ocean regime.

Kiefer, Walter S.↗
NASA NTRS2020

Dynamical Evolution of Simulated Particles Ejected from Asteroid Bennu

In early 2019, the OSIRIS-REx spacecraft discovered small particles being ejected from the surface of the near-Earth asteroid Bennu. Although they were seen to be ejected at slow speeds, on the order of tens of cm/s, a number of particles were surprisingly seen to orbit for multiple revolutions and days, which requires a dynamical mechanism to quickly and substantially modify the orbit to prevent re-impact upon their first periapse passage. This paper demonstrates that, based on simulations constrained by the conditions of the observed events, the combined effects of gravity, solar radiation pressure, and thermal radiation pressure from Bennu can produce many sustained orbits for ejected particles. Furthermore, the simulated populations exhibit two interesting phenomena that could play an important role in the geophysical evolution of bodies such as Bennu. First, small particles (< 1 cm radius) are preferentially removed from the system, which could lead to a deficit of such particles on the surface. Second, re-impacting particles preferentially land near or on the equatorial bulge of Bennu. Over time, this can lead to crater in-filling and growth of the equatorial radius without requiring landslides.

Jay W. McMahon↗
NASA NTRS2020

Detection of a Satellite of the Trojan Asteroid (3548) Eurybates – A Lucy Mission Target

We describe the discovery of a satellite of the Trojan asteroid (3548) Eurybates in images obtained with the Hubble Space Telescope. The satellite was detected on three separate epochs, two in September 2018 and one in January 2020. The satellite has a brightness in all three epochs consistent with an effective diameter of d2=1.2±0.4km. The projected separation from Eurybates was s~1700-2300 km and varied in position, consistent with a large range of possible orbits. Eurybates is a target of the Lucy Discovery mission and the early detection of a satellite provides an opportunity fora significant expansion of the scientific return from this encounter.

K. S. Noll↗
NASA NTRS2020

Asteroid (101955) Bennu’s Weak Boulders and Thermally Anomalous Equator

Thermal inertia and surface roughness are proxies for the physical characteristics of planetary surfaces. Global maps of these two propertiesdistinguish the boulder population on near-Earth asteroid (NEA) (101955)Bennuinto two typesthat differ in strength,andboth havelower thermal inertiathan expectedfor boulders and meteorites. Neither has strongly temperature-dependent thermal properties. The weakerbouldertypeprobably would not survive atmospheric entry and thus may not berepresented in the meteorite collection. The maps also show ahigh-thermal-inertia band at Bennu’s equator, which might be explained by processes such as compaction or strength sorting during mass movement, but these explanations are not wholly consistent with other data. Our findings imply that other C-complex NEAs likely have boulderssimilar to those on Bennu,rather than finer-particulate regoliths.A tentative correlation between albedo and thermal inertia of C-complex NEAs may be due to relative abundances of boulder types.

B Rozitis↗
NASA NTRS1992

Deflection and Fragmentation of Near-Earth Asteroids

Collisions by near-earth asteroids or the nuclei of comets pose varying levels of threat to man. A relatively small object, approximately 100 m diameter, which might be found on an impact trajectory with a populated region of the Earth, could potentially be diverted with a velocity of approximately1 cm/sec from an Earth impacting trajectory by impact (at 12 km/sec) by a rocket launched, 10^2 to 10^3 Kg impactor. For larger bodies, the use of kinetic energy impactors appear impractical because of the larger mass requirement. For any size object, nuclear explosions appear to be more efficient, using either the prompt blow-off from neutron radiation, the impulse from ejecta of a near-surface explosion for deflection, or, least efficiently, as a fragmenting charge.

Harris, Alan W.↗
NASA NTRS2012

NASA'S concept for a human mission to a near-earth asteroid : preference tradeoffs for the surveyor decision problem

NASA's recent attention and interest in sending a human mission to land on a Near-Earth asteroid raised the question of whether to first send a robotic surveyor. This paper describes a Bayesian approach for comparing the value and cost-risk tradeoffs of sending (versus not sending) surveyor missions prior to a human mission. A multiattribute decision analysis approach was used to account for both mission value and cost in each of 27 hypothetical risk-attitude cases corresponding to an emphasis on mission value; equal priority between mission value and cost; and an emphasis on cost. The decisions implied by the different strategic viewpoints are described.

Smith, Jeffrey H.↗
NASA NTRS2017

Extension of MBSE for Project Programmatics Management on the Asteroid Redirect Robotic Mission

Model-based Systems Engineering can be employed beyond management of the technical architecture development of a system to also manage the programmatics associated with Systems Engineering activities of a project. On NASA’s Asteroid Redirect Robotic Mission, MBSE has been successfully employed to manage, generate, and interact with the documentation-based deliverables associated with System Engineering activities. This has been involved in defining and tracking project document, milestone, and personnel metadata via the same modeling framework used for the technical architecture management. Additionally, it has focused on improving overall user experiences through linkage of documentation to technical content in the system model, automation of manually intensive tasks, and others stakeholderoriented features.

Mozafari, Tanaz↗
NASA NTRS2018

Double Asteroid Redirection Test (DART) Mission Design and Navigation for Low Energy Escape

This paper describes the evolution of the NASA Double Asteroid Redirection Test (DART) mission design and navigation. Specifically, the mission has been conceived as (1) a hydrazine bus on a ballistic trajectory, (2) a low-thrust bus launching from a geostationary transfer orbit and spiraling to escape, and (3) a lowthrust bus that launches with a small positive escape energy. This paper discusses the rationale in favor of the third concept, low energy escape, and describes the key mission design and navigation studies. In an effort to be compatible with an unknown co-manifest partner, the trajectory design must account for a large range of launch energies, orientations, and dates. The navigation approach must account for sensitive regions in the trajectory and plan for both low-thrust and chemical phases of flight. These findings are relevant to other missions pursuing low-cost interplanetary rideshare concepts.

Grebow, Daniel↗
NASA NTRS2019

Near earth asteroid scout CubeSat science data retrieval optimization using onboard data analysis

We present a collection of techniques designed for mitigating limited pointing stability for target acquisition, onboard image calibration and decision making, in a low bandwidth environment. These technologies will fly on the Near Earth Asteroid Scout (NEA Scout) interplanetary CubeSat mission in 2019. To support verification and validation, the flight software implementations of these algorithms have been run on New Horizons, Rosetta and terrestrially acquired data sets. These experiments validate the capability to detect the target, through noise and target location uncertainty.

Basset, Christophe↗
NASA NTRS2020

Hemispherical differences in the shape and topography of asteroid (101955) Bennu

We investigate the shape of near-Earth asteroid (101955) Bennu by constructing a high-resolution (20 cm) global digital terrain model from laser altimeter data. By modeling the northern and southern hemispheres separately, we find that longitudinal ridges previously identified in the north extend into the south but are obscured there by surface material. In the south, more numerous large boulders effectively retain surface materials and imply a higher average strength at depth to support them. The north has fewer large boulders and more evidence of boulder dynamics (toppling and downslope movement) and surface flow. These factors result in Bennu's southern hemisphere being rounder and smoother, whereas its northern hemisphere has higher slopes and a less regular shape. We infer an originally asymmetric distribution of large boulders followed by a partial disruption, leading to wedge formation in Bennu's history.

M. G. Daly↗