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At least 19 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1988

Trojan and Hilda asteroid lightcurves. I - Anomalously elongated shapes among Trojans (and Hildas?)

A comparison of the available sample of lightcurves for 26 Trojan and Hilda asteroids with belt asteroid lightcurves shows the former to be distinguished by a higher incidence of high amplitudes rgan belt asteroids of comparable size, suggesting more elongated shapes; they currently have, moreover, only a few percent of the main-belt asteroids' collision frequency. A more modest collisional evolution that may have affected the relative degree of fragmentation of these bodies, and thus their shapes, is inferred.

Hartmann, William K.↗
DOE OSTI2025

A Survey on the Design, Detection, and Prevention of Pre-Silicon Hardware Trojans

The complexity of the semiconductor design lifecycle and globalized manufacturing process creates concern over the threat of deliberate malicious alterations, or hardware Trojans, being inserted into microelectronic designs. This has resulted in a significant corpus of hardware Trojan research including Trojan design and benchmarking efforts and development of corresponding metrics and detection and prevention techniques, over the last two decades. In this survey, we first highlight efforts in Trojan design and benchmarking, followed by a cataloging of seminal and recent works in Trojan detection and prevention and their accompanied metrics. Given the volume of literature in this field, this survey considers only pre-silicon techniques. We make this distinction between pre- and post-silicon to properly scope and provide appropriate context into the capabilities of existing hardware Trojan literature. Each major section (design, prevention, and detection) is accompanied by insights, and common pitfalls, which we highlight can be addressed by future research.

42 ENGINEERING↗
NASA NTRSDate not supplied

Terminal Tracking for the Lucy Trojan Asteroid Mission

The most recent NASA Discovery class mission to fly is the Lucy mission to the Trojan Asteroids of Jupiter. Launched in October of 2021, Lucy’s destination will be the unexplored Jupiter Trojan Asteroids that orbit the Sun at the stable L4 and L5 points ahead of, and behind Jupiter. This 12-yearmission will perform close flybys of 1 main belt asteroid, Donaldjohanson, and 7 Trojans asteroids: Eurybates and its satellite Queta, Polymele, Leucus, Orus, and the near equal mass Trojan binary pair, Patroclus andMenoetius. The large distance from earth for the encounters, the high relative velocities and sun incidence angles on approach,and the limited number of Earth observations of the Trojans,make the delivery knowledge highly uncertain. To reduce the delivery uncertainties and maximize science return, Lucy employs a Terminal Tracking System consisting of optical imaging, centroiding and state estimation of the Trojan asteroids on approach and through close approach. This paper presents the Lucy Terminal Tracking System implementation, a brief overview of the mission and the GN&C subsystem.

Philip G Good↗
NASA NTRS1992

The Trojan

The Trojan is the culmination of thousands of engineering person-hours by the Cones of Silence Design Team. The goal was to design an economically and technologically viable supersonic transport. The Trojan is the embodiment of the latest engineering tools and technology necessary for such an advanced aircraft. The efficient design of the Trojan allows for supersonic cruise of Mach 2.0 for 5,200 nautical miles, carrying 250 passengers. The per aircraft price is placed at $200 million, making the Trojan a very realistic solution for tomorrows transportation needs. The following is a detailed study of the driving factors that determined the Trojan's super design.

Source record↗
NASA NTRS2015

Investigating Trojan Asteroids at the L4/L5 Sun-Earth Lagrange Points

Investigations of Earth's Trojan asteroids will have benefits for science, exploration, and resource utilization. By sending a small spacecraft to the Sun-Earth L4 or L5 Lagrange points to investigate near-Earth objects, Earth's Trojan population can be better understood. This could lead to future missions for larger precursor spacecraft as well as human missions. The presence of objects in the Sun-Earth L4 and L5 Lagrange points has long been suspected, and in 2010 NASA's Wide-field Infrared Survey Explorer (WISE) detected a 300 m object. To investigate these Earth Trojan asteroid objects, it is both essential and feasible to send spacecraft to these regions. By exploring a wide field area, a small spacecraft equipped with an IR camera could hunt for Trojan asteroids and other Earth co-orbiting objects at the L4 or L5 Lagrange points in the near-term. By surveying the region, a zeroth-order approximation of the number of objects could be obtained with some rough constraints on their diameters, which may lead to the identification of potential candidates for further study. This would serve as a precursor for additional future robotic and human exploration targets. Depending on the inclination of these potential objects, they could be used as proving areas for future missions in the sense that the delta-V's to get to these targets are relatively low as compared to other rendezvous missions. They can serve as platforms for extended operations in deep space while interacting with a natural object in microgravity. Theoretically, such low inclination Earth Trojan asteroids exist. By sending a spacecraft to L4 or L5, these likely and potentially accessible targets could be identified.

John, K. K.↗
NASA NTRS1977

Radii and albedos of four Trojan asteroids and Jovian satellites 6 and 7

Results are reported for radiometric measurements of broadband 20-micron fluxes from the Trojan asteroids 617 Patroclus, 624 Hektor (for which the broadband 10-micron flux was also measured), 1172 Aeneas, and 1173 Anchises as well as from the outer Jovian satellites Himalia (J6) and Elara (J7). Geometric albedos and radii for the six objects are derived from the corrected monochromatic fluxes and visual magnitudes. It is found that all the objects have exceedingly low geometric albedos, indicating that the Trojans and possibly the outer Jovian satellites constitute a distinct class of small solar-system bodies. The composition of the Trojan asteroids is considered on the basis of available sizes, albedos, and shapes. Revised tables of the albedos and radii of all the Jovian satellites are presented. It is concluded that the Trojans are not composed primarily of ice and that an asteroidal origin for the comets of the Jupiter group is unlikely.

Cruikshank, D. P.↗
NASA NTRS1991

A CCD comparison of outer Jovian satellites and Trojan asteroids

The eight small outer Jovian satellites are not as well known as the brighter, more illustrious Galilean satellites. They are divided into two groups, each containing four satellites; the inner group travels in prograde orbits while the outer group travels in retrograde orbits. From the distinct orbital characteristics of the two groups, most of the theories of their origin involve the capture and breakup of two planetesimals upon entry into the atmosphere of proto-Jupiter. Their proximity to the Trojans asteroids has led to conjectures of a link between them and the Trojans. However, Tholen and Zellner (1984) found no red spectrum among six of the satellites and postulated that they were all C-type objects; therefore, they were unlikely to be derivatives of the Trojan population. Charge-coupled device (CCD) photometry and spectroscopy of the eight outer Jovian satellites obtained from 1987 to 1989 and a comparison between these eight satellites and the Trojan asteroids are presented.

Luu, Jane X.↗
NASA NTRS1992

Trojan, Hilda, and Cybele asteroids - New lightcurve observations and analysis

Lightcurve observations of 23 Trojan, Hilda, and Cybele asteroids are presently subjected to a correction procedure for multiple-aspect lightcurves, followed by a quantitative, bias-corrected analysis of lightcurve amplitude distributions for all published data on these asteroids. While the largest Trojans are found to have a higher mean-lightcurve amplitude than their low-albedo, main-belt counterparts, the smaller Trojans and all Hildas and Cybeles display lightcurve properties resembling main-belt objects. Only the largest Trojans have retained their initial forms after subsequent collisional evolution; 90 km may accordingly represent a transitional magnitude between primordial objects and collision fragments.

Binzel, Richard P.↗
NASA NTRS2019

Trajectory Design of the Lucy Mission to Explore the Diversity of the Jupiter Trojans

Lucy, NASA’s next Discovery-class mission, will explore the diversity of the Jupiter Trojan asteroids. The Jupiter Trojans are thought to be remnants of the early solar system that were scattered inward when the gas giants migrated to their current positions as described in the Nice model. There are two stable subpopulations, or “swarms,” captured at the Sun-Jupiter L4 and L5 regions. These objects are the most accessible samples of what the outer solar system may have originally looked like. Lucy will launch in 2021 and will visit five Trojans, including one binary system. This paper discusses the target selection process, including a description of “alternate Lucys” that were ultimately passed over in favor of the final design. The mathematics of the trajectory optimization are also discussed.

Lucy↗
NASA NTRS1978

The nature of Trojan asteroid 624 Hektor

Near-simultaneous visual and thermal IR (20-micron) photometry of the Trojan asteroid 624 Hektor is reported which was performed when the asteroid was observed nearly along its rotation axis. The results confirm and refine the low albedo and large size of this asteroid and confirm the general rotational-pole position and aspect angle predicted by Dunlap and Gehrels (1969). Hektor is found to be a truly extraordinary object in that it is larger and far more irregular in shape than other measured Trojans and far more irregular than other belt asteroids of comparable size. It is proposed that Hektor could be a partially coalesced pair of Trojan asteroids which collided with energy too low to cause complete fragmentation, thus forming a dumbbell-shaped object. A possible scenario is outlined according to which the two pre-Hektor objects were neighboring relatively large primitive spheroidal planetesimals trapped in Jupiter's Lagrangian cloud. Observational and theoretical tests of this model are suggested.

Hartmann, W. K.↗
NASA NTRS1991

The 1990 MB: The first Mars Trojan

Asteroid 1990 MB was discovered by D. H. Levy and H. E. Holt during the course of the Mars and Earth Crossing Asteroid and Comet Survey. An orbit based on a 9 day arc and the asteroid's location near Mars' L5 (trailing Lagrangean) longitude led E. Boswell to speculate that it might be in 1:1 resonance with Mars, analogous to the Trojan asteroids of Jupiter. Subsequent observations strengthened the possibility, and later calculations confirmed it. Thus 1990 MB is the first known asteroid in 1:1 resonance with a planet other than Jupiter. The existence of 1990 MB (a small body most likely between 2 and 4 km in diameter) provides remarkable confirmation of computer simulations. These self consistent n-body simulations demonstrated this sort of stability for Trojans of all the terrestrial planets over at least a 2 million year time base. The discovery of 1990 MB suggests that others of similar or smaller diameter may be found. Using hypothetical populations of Mars Trojans, their possible sky plane distributions were modeled as a first step in undertaking a systematic observational search of Mars' L4 and L5 libration regions.

Innanen, Kimmo A.↗
NASA NTRS1991

Mapping the stability field of Jupiter Trojans

Jupiter Trojans are a remnant of outer solar system planetesimals captured into stable or quasistable libration about the 1:1 resonance with the mean motion of Jupiter. The observed swarms of Trojans may provide insight into the original mass of condensed solids in the zone from which the Jovian planets accumulated, provided that the mechanisms of capture can be understood. As the first step toward this understanding, the stability field of Trojans were mapped in the coordinate proper eccentricity, e(sub p), and libration amplitude, D. To accomplish this mapping, the orbits of 100 particles with e(sub p) in the range of 0 to 0.8 and D in the range 0 to 140 deg were numerically integrated. Orbits of the Sun, the four Jovian planets, and the massless particles were integrated as a full N-body system, in a barycentric frame using fourth order symplectic scheme.

Levison, H. F.↗
NASA NTRS1992

JHK photometry of selected Trojan and Hilda asteroids

No entirely satisfactory match has been established between the present JHK photometry of selected Hilda and Trojan asteroids and photometry for both main belt asteroids and laboratory samples. It is noted that while the leading Trojans and Hildas exhibit similar and homogeneous JHK colors, the trailing Trojans appear to be more heterogeneous. Charcoal and magnetite provide the best match in terms of JHK colors.

Smith, Dale W.↗
NASA NTRS2003

Spectroscopy and Photometry of Mars Trojans

Mars is the only terrestrial planet known to have co-orbiting "Trojan" asteroids. We have obtained visible and near-IR reflectance spectra of three of these objects: 5261 Eureka and 1998 VF31 in the L5 region and 1999 UJ7 in the L4 region. We also obtained JHK spectrophotometry and a visible lightcurve for 5261 Eureka. The asteroid 5261 Eureka has a visible spectrum that is classified as Sr in the Bus taxonomy, and has infrared colors consistent with the A-class asteroids. The data for 1998 VF31 have a restricted wavelength range, but are most consistent with the Sr or Sa class, though we note a marginal consistency with the D class. We can rule out a C-class classification. 1999 UJ7 has an X-class or T-class spectrum, which is unlike that of the other two Mars Trojans. The photometric data for Eureka are limited, but we can constrain the period to longer than 5 hours (likely 5.556 hours) and lightcurve amplitude of at least 0.15 magnitude at this viewing geometry. The spectral differences among the Mars Trojans suggests that either they did not all form at their present solar distances or that they have not always been at their present sizes. 0 2003 Elsevier Inc. All rights reserved. Keywords: Asteroids; Asteroids, composition; Spectroscopy; Satellites of Mars

Rivkin, A. S.↗
NASA NTRS2003

Spectroscopy and Photometry of Mars Trojans

Mars is the only terrestrial planet known to have co-orbiting Trojan asteroids. We have obtained visible and near-IR reflectance spectra of three of these objects: 5261 Eureka and 1998 VF31 in the L5 region and 1999 UJ7 in the LA region. We also obtained JHK spectrophotometry and a visible lightcurve for 5261 Eureka. The asteroid 5261 Eureka has a visible spectrum that is classified as Sr in the Bus taxonomy, and has infrared colors consistent with the A-class asteroids. The data for 1998 VF31 have a restricted wavelength range, but are most consistent with the Sr or Sa class, though we note a marginal consistency with the D class. We can rule out a C-class classification. 1999 UJ7 has an X-class or T-class spectrum, which is unlike that of the other two Mars Trojans. The photometric data for Eureka are limited, but we can constrain the period to longer than 5 hours (likely 5.5-6 hours) and lightcurve amplitude of at least 0.15 magnitude at this viewing geometry. The spectral differences among the Mars Trojans suggests that either they did not all form at their present solar distances or that they have not always been at their present sizes.

Rivkin, A. S.↗
NASA NTRS2013

Automated Design of Propellant-Optimal, End-to-End, Low-Thrust Trajectories for Trojan Asteroid Tours

The Sun-Jupiter Trojan asteroids are celestial bodies of great scientific interest as well as potential resources offering water and other mineral resources for longterm human exploration of the solar system. Previous investigations under this project have addressed the automated design of tours within the asteroid swarm. This investigation expands the current automation scheme by incorporating options for a complete trajectory design approach to the Trojan asteroids. Computational aspects of the design procedure are automated such that end-to-end trajectories are generated with a minimum of human interaction after key elements and constraints associated with a proposed mission concept are specified.

Trojan asteroid↗
NASA NTRS1995

Multiple Encounter Missions with the Trojan and Main Belt Asteroids

The clustering of asteroids, the Trojans, at the Jupiter liberation points L4 and L5 offer yearly launch opportunities for double flybys. Also, passage through the main belt can add one or two additional flybys to make this an attractive mission for small spacecraft. The Trojans represent important clusters of main-belt sized bodies. This study explores the possibilities of multiple asteroid encounters.

astrodynamics↗
NASA NTRS1990

Comet nuclei and Trojan asteroids - A new link and a possible mechanism for comet splittings

Relatively elongated shapes, implied by recent evidence of a greater incidence of high amplitude lightcurves for comet nuclei and Trojan asteroids than for similarly scaled main belt asteroids, are suggested to have evolved among comet nuclei and Trojans due to volatile loss. It is further suggested that such an evolutionary course may account for observed comet splitting; rotational splitting may specifically occur as a result of evolution in the direction of an elongated shape through sublimation. Supporting these hypotheses, the few m/sec separation velocities projected for rotationally splitting elongated nuclei are precisely in the observed range.

Hartmann, William K.↗