The 2019 Taurid resonant swarm: prospects for ground detection of small NEOs
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David L Clark↗
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Solar Rotation Effects in Earth's and Mars' Thermospheric Densities as Revealed by Concurrent MAVEN, Swarm‐C, and GOES Observations
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F. Gasperini↗
Computationally Efficient Collision-Free Trajectory Planning of Satellite Swarms Under Unmodeled Orbital Perturbations
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Himadri Basu↗
Surge current and electron swarm tunnel tests of thermal blanket and ground strap materials
The results are described of a series of current conduction tests with a thermal control blanket to which grounding straps have been attached. The material and the ground strap attachment procedure are described. The current conduction tests consisted of a surge current examination of the ground strap and a dilute flow, energetic electron deposition and transport through the bulk of the insulating film of this thermal blanket material. Both of these test procedures were used previously with thermal control blanket materials.
Hoffmaster, D. K.↗
Effect of solar radiation on a swarm of meteoric particles
The theory of the Poynting-Robertson effect is used to study the motion of meteors relative to a parent comet describing an undisturbed elliptical orbit. It is shown that any emitted particle proceeds to move retrogressively away from the comet to a certain maximum angular distance (as seen from the sun) depending on its sigma-s value, and then undergoes relative motion in the opposite forward direction. The time taken to reach this greatest elongation behind the comet is the same for all particles, and after twice this time the particles will have returned to zero angular displacement relative to the comet. For comet Encke the time for the elongation to return to zero is about 6600 y; for Halley it is about 200,000 y; for Temple-Tuttle (1965 IV) it is just over 100,000 y.
Lyttleton, R. A.↗
Cometary and meteorite swarm impact on planetary surfaces
The impact-induced deformation from hypothetical cometary objects having initial densities in the 0.01 to 1 g/cu cm range and heats of vaporization in the approximately 2 kJ/g (corresponding to water) to approximately 10 to the 7th J/g range is examined for impacts in the 5 to 45 km/s range. Even though the direct effect of an atmosphere is neglected, the atmosphere may in fact cause a cometary object to break up into a shower or equivalent very porous impactor. Besides examining the partitioning of impact energy into internal energy of the impacted planet and impacting cometary material, calculations are made of the relative efficiency of shock-induced melting and vaporization by comets on planetary surface materials and the mass loss from a given planet for various escape velocities.
Okeefe, J. D.↗
Models of Angular Momentum Input to a Circumterrestrial Swarm from Encounters with Heliocentric Planetesimals
Models of lunar origin in which the Moon accretes in orbit about the Earth from material approaching the Earth from heliocentric orbits must overcome a fundamental problem: the approach orbits of such material would be, in the simplest approximation, equally likely to be prograde or retrograde about the Earth, with the result that accretion of such material adds mass but not angular momentum to circumterrestrial satellites. Satellite orbits would then decay due to the resulting drag, ultimately impacting onto the Earth. One possibility for adding both material and angular momentum to Earth orbit is investigated: imbalance in the delivered angular momentum between pro and retrograde Earth passing orbits which arises from the three body dynamics of planetesimals approaching the Earth from heliocentric space. In order to study angular momentum delivery to circumterrestrial satellites, the near Earth velocities were numerically computed as a function of distance from the Earth for a large array of orbits systematically spanning heliocentric phase space.
Davis, D. R.↗
Thickness of the particle swarm in cosmic ray air showers
The average dispersion in arrival time of air shower particles detected with a scintillator at an impact parameter r is described with accuracy 5-10% by the empirical formula sigma = Sigma sub to (1+r/r sub t) sup b, where Sigma sub to = 2.6 ns, r sub t = 30m and b = (1.94 + or - .08) (0.39 + or - .06) sec Theta, for r 2 km, 10 to the 8th power E 10 to the 11th power GeV, and Theta 60 deg. (E is the primary energy and theta is the zenith angle). The amount of fluctuation in sigma sub t due to fluctuations in the level of origin and shower development is less than 20%. These results provide a basis for estimating the impact parameters of very larger showers with data from very small detector arrays (mini-arrays). The energy of such showers can then be estimated from the local particle density. The formula also provides a basis for estimating the angular resolution of air shower array-telescopes.
Linsley, J.↗
Accumulation of a swarm of small planetesimals
The present gasdynamic study of the planetesimal-accumulation stage in which 10-km bodies in the neighborhood of 1 AU grow to 10 to the 25th-10 to the 27th g mass, or 'planetary embryo' size, attempts to identify the circumstances under which runaway growth forms a small number of massive embryos in the terrestrial-planet region on a 0.1-1.0 million year time-scale. No runaways are found, however, unless more plausible physical processes are invoked; in that case, runaways in the terrestrial planet region are probable on a 0.1 million-year time-scale, and the final stage of planetary accumulation may involve the growth of these embryos into the present planets on a 10-100 million-year time-scale.
Wetherill, G. W.↗
Stirring of a planetesimal swarm - The role of distant encounters
The viscous stirring algorithm developed by Stewart and Wetherill (1988) to treat the random velocities induced in planetesimals by their mutual gravitational perturbations encompasses only the scattering of bodies in crossing orbits by close encounters. Expressions are presently derived for the stirring rate due to distant encounters on the basis of three-body formalism, using a stirring rate that has the same mass-dependence as that for close encounters. The relative importance of both the close encounter and distant encounter mechanisms depends on the Safronov number. Perturbations by a planetary embryo in scenarios that involve explosive growth are found capable of affecting planetesimal evolution in noncrossing orbits.
Weidenschilling, Stuart J.↗
Multizone accretional evolution of planetesimal swarms
The general features of a new numerical simulation of planetesimal accretion which models multiple heliocentric distance zones, together with a detailed model for the planetesimal size and orbital distribution in each zone, are described. A restricted version of this model which allows only a single heliocentric distance zone has been used to test the validity of the code by comparing with results from earlier authors when the same physical phenomena are included. Generally, very good agreement is found.
Spaute, D.↗
Determining stress states using dike swarms: The Lauma Dorsa example
Initial examination of the Magellan coverage of Venus has revealed between 150 and 300 large, radially lineated landforms distributed across the planet's surface. Where the lineaments have been examined in detail, the majority fail to exhibit signatures indicative of relief at or above the resolution of the radar; however, when the sense of topographic relief may be ascertained, the lineaments commonly appear as fissures or flat-floored trenches interpreted as graben. Individual lineaments can display graben, fissure, and zero relief behavior along their length, suggesting either that these differences are a function of the resolution of the radar, or that the morphological distinctions are real but somehow genetically linked. In many instances, radial lineaments exhibiting these characteristics are directly associated with surface volcanism, including flanking and terminal flows, superimposed shield domes and pit chains, and central, calderalike topographic lows. These observable characteristics, as well as theoretical studies and comparison with similar terrestrial features, have led to the working hypothesis that many of the radial fracture systems on Venus are the surface manifestation of subsurface dikes propagating laterally from a central magma source. If this interpretation is correct, studies of terrestrial dikes suggest that the lineament directions, with localized exceptions and barring subsequent deformation, should be perpendicular to the orientation of the least compressive stress at the time of their formation. To test this hypothesis, we briefly examine a radial fracture system (63.7 degrees N, 195 degrees E) located between two deformation belts in Vinmara Planitia, and verify that the lineaments to the east behave in the expected manner. We have also chosen this feature, however, because of its proximity to Lauma Dorsa to the west. On the basis of Venera 15/16 data, both compressional and extensional origins for this deformation belt have been proposed. By examining the stratigraphy and applying our interpretation that the fracture system is linked to the presence of subsurface dikes, we present an independent evaluation of the stress state associated with Lauma Dorsa, and thus contribute to the assessment of its origin.
Grosfils, Eric B.↗
Swarm autonomic agents with self-destruct capability
Systems, methods and apparatus are provided through which in some embodiments an autonomic entity manages a system by generating one or more stay alive signals based on the functioning status and operating state of the system. In some embodiments, an evolvable synthetic neural system is operably coupled to one or more evolvable synthetic neural systems in a hierarchy. The evolvable neural interface receives and generates heartbeat monitor signals and pulse monitor signals that are used to generate a stay alive signal that is used to manage the operations of the synthetic neural system. In another embodiment an asynchronous Alice signal (Autonomic license) requiring valid credentials of an anonymous autonomous agent is initiated. An unsatisfactory Alice exchange may lead to self-destruction of the anonymous autonomous agent for self-protection.
Hinchey, Michael G.↗
Swarm autonomic agents with self-destruct capability
Systems, methods and apparatus are provided through which in some embodiments an autonomic entity manages a system by generating one or more stay alive signals based on the functioning status and operating state of the system. In some embodiments, an evolvable synthetic neural system is operably coupled to one or more evolvable synthetic neural systems in a hierarchy. The evolvable neural interface receives and generates heartbeat monitor signals and pulse monitor signals that are used to generate a stay alive signal that is used to manage the operations of the synthetic neural system. In another embodiment an asynchronous Alice signal (Autonomic license) requiring valid credentials of an anonymous autonomous agent is initiated. An unsatisfactory Alice exchange may lead to self-destruction of the anonymous autonomous agent for self-protection.
Hinchey, Michael G.↗
NASAs EDSN Aims to Overcome the Operational Challenges of CubeSat Constellations and Demonstrate an Economical Swarm of 8 CubeSats Useful for Space Science Investigations
Operators of a constellation of CubeSats have to confront a number of daunting challenges that can be cost prohibitive, or operationally prohibitive, to missions that could otherwise be enabled by a satellite constellation. Challenges including operations complexity, intersatellite communication, intersatellite navigation, and time sharing tasks between satellites are all complicated by operating with the usual CubeSat size, power, and budget constraints. EDSN pioneers innovative solutions to these problems as they are presented on the nano-scale satellite platform.
CubeSat↗
Formation Flying/Satellite Swarm Concept Project
NASA needs a method of not only propelling and rotating small satellites, but also to track their position and orientation. We propose a concept that will, for the first time, demonstrate both tracking and propulsion simultaneously in the same system.
Technology Portfolio Project↗
SmallSat Precision Navigation with Low-Cost MEMS IMU Swarms
The continued advancement of small satellite-based science missions requires the solution to a number of important technical challenges. Of particular note is that small satellite missions are characterized by tight constraints on cost, mass, power, and volume that make them unable to fly the high-quality Inertial Measurement Units (IMUs) required for orbital missions demanding precise orientation and positioning. Instead, small satellite missions typically fly low-cost Micro-Electro-Mechanical System (MEMS) IMUs. Unfortunately, the performance characteristics of these MEMS IMUs make them ineffectual in many spaceflight applications when employed in a single IMU system configuration.
Precision navigation↗