scholarly journals Libration-induced Orbit Period Variations Following the DART Impact

2021 ◽  
Vol 2 (6) ◽  
pp. 242
Author(s):  
Alex J. Meyer ◽  
Ioannis Gkolias ◽  
Michalis Gaitanas ◽  
Harrison F. Agrusa ◽  
Daniel J. Scheeres ◽  
...  
Keyword(s):  
Momentum Transfer ◽  
Binary Asteroid ◽  
Long Period ◽  
Short Period ◽  
Planetary Defense ◽  
Period Variations ◽  
Post Impact ◽  
Binary Asteroid System ◽  
Orbit Period ◽  
The Impact

Abstract The Double Asteroid Redirection Test (DART) mission will be the first test of a kinetic impactor as a means of planetary defense. In late 2022, DART will collide with Dimorphos, the secondary in the Didymos binary asteroid system. The impact will cause a momentum transfer from the spacecraft to the binary asteroid, changing the orbit period of Dimorphos and forcing it to librate in its orbit. Owing to the coupled dynamics in binary asteroid systems, the orbit and libration state of Dimorphos are intertwined. Thus, as the secondary librates, it also experiences fluctuations in its orbit period. These variations in the orbit period are dependent on the magnitude of the impact perturbation, as well as the system’s state at impact and the moments of inertia of the secondary. In general, any binary asteroid system whose secondary is librating will have a nonconstant orbit period on account of the secondary’s fluctuating spin rate. The orbit period variations are typically driven by two modes: a long period and a short period, each with significant amplitudes on the order of tens of seconds to several minutes. The fluctuating orbit period offers both a challenge and an opportunity in the context of the DART mission. Orbit period oscillations will make determining the post-impact orbit period more difficult but can also provide information about the system’s libration state and the DART impact.

scholarly journals On the secondary’s rotation in a synchronous binary asteroid

2020 ◽  
Vol 493 (1) ◽  
pp. 171-183
Author(s):  
H S Wang ◽  
X Y Hou
Keyword(s):  
Periodic Orbits ◽  
Body Problem ◽  
Spin Orbit ◽  
Binary Asteroid ◽  
Classical Spin ◽  
Long Period ◽  
Period Orbit ◽  
Short Period ◽  
Orbit Eccentricity ◽  
Binary Asteroid System

ABSTRACT This article studies the secondary’s rotation in a synchronous binary asteroid system in which the secondary enters the 1:1 spin-orbit resonance. The model used is the planar full two-body problem, composed of a spherical primary plus a triaxial ellipsoid secondary. Compared with classical spin-orbit work, there are two differences: (1) influence of the secondary’s rotation on the mutual orbit is considered and (2) instead of the Hamiltonian approach, the approach of periodic orbits is adopted. Our studies find the following. (1) The genealogy of the two families of periodic orbits is the same as that of the families around triangular libration points in the restricted three-body problem. That is, the long-period family terminates on to a short-period orbit travelling N times. (2) In the limiting case where the secondary’s mass is negligible, our results can be reduced to classical spin-orbit theory, by equating the long-period orbit with free libration and the short-period orbit with the forced libration caused by orbit eccentricity. However, the two models show obvious differences when the secondary’s mass is non-negligible. (3) By studying the stability of periodic orbits for a specific binary asteroid system, we are able to obtain the maximum libration amplitude of the secondary (which is usually less than 90°) and the maximum mutual orbit eccentricity that does not break the secondary’s synchronous state. We also find an anti-correlation between the secondary’s libration amplitude and the orbit eccentricity. The (65803) Didymos system is taken as an example to show the results.

On the post-impact spin state of the secondary component of the Didymos-Dimorphos binary asteroid system

2020 ◽  
Author(s):  
Harrison Agrusa ◽  
Kleomenis Tsiganis ◽  
Ioannis Gkolias ◽  
Derek Richardson ◽  
Alex Davis ◽  
...  
Keyword(s):  
Spin State ◽  
Uniform Density ◽  
Dynamical Structure ◽  
Spin Orbit ◽  
Binary Asteroid ◽  
Planetary Defense ◽  
Out Of Plane ◽  
Post Impact ◽  
Binary Asteroid System ◽  
Binary Orbit

<p>NASA’s Double Asteroid Redirection Test (DART) is designed to be the first demonstration of a kinetic impactor for planetary defense against a small body impact hazard. The target is the smaller component of the Didymos-Dimorphos binary asteroid system. The DART impact will abruptly change the relative velocity of the secondary (Dimorphos), increasing the binary eccentricity and exciting librations in the secondary. The observed change in the binary orbit period will be used to infer the “beta factor”, or the momentum transfer efficiency, an important parameter used in planetary defense. The post-impact spin and librational dynamics are expected to be highly dependent on the momentum transferred to the target (i.e., beta) and the shape of the secondary, which is still unconstrained.</p> <p>In this work, we explore the possible post-impact spin state of Dimorphos, as a function of its shape and beta, assuming it has an ellipsoidal shape and that both bodies have a uniform density. We have conducted attitude dynamics simulations with a modified 3-D spin-orbit model, accounting for the secondary’s shape and the primary’s oblateness, to understand the underlying dynamical structure of the system. In addition, we have used the radar-derived polyhedral shape model of Didymos in high-fidelity Full Rigid Two-Body Problem (FR2BP) simulations to capture the fully three-dimensional nature of the problem. We consider the outcomes from a simplified planar impact, where the DART momentum is transferred within the binary orbit plane, opposite the motion of Dimorphos, in addition to a more realistic case that accounts for the full DART velocity vector (which contains out-of-plane components).</p> <p>With both simulation tools, we produce the expected signatures of the 1:1 and 2:1 secondary resonances between the free and forced libration periods, corresponding to axial ratios of a/b = 1.414 and a/b = 1.087, respectively. For moderate values of beta (~3), we find that the libration amplitude can exceed ~40 degrees in most cases. For some possible axial ratios, it is even possible to achieve a libration amplitude exceeding 40 degrees with beta values as low as 1. In addition, both codes reveal that the secondary may be attitude unstable in many cases, and can enter a chaotic tumbling state for larger values of beta (~5). In some cases, Dimorphos is able to break from its assumed 1:1 spin-orbit resonance.</p> <p>In the case with a more realistic impact geometry (where some momentum is transferred out-of-plane), the results are relatively similar. The most noticeable difference is in the cases that result in a chaotic tumbling state. In those cases, the characteristic timescale for entering the chaotic tumbling state is much shorter – typically only several orbit periods are required. We also discuss the feasibility of detecting the post-impact spin state of Dimorphos with ground-based observations.</p> <p>This study was supported in part by the DART mission, NASA Contract # NNN06AA01C to JHU/APL. The work of K.T. and I.G. is supported by the EC Horizon 2020 research and innovation programme, under grant agreement No. 870377 (project "NEO-MAPP"). Some of the simulations herein were carried out on The University of Maryland Astronomy Department’s YORP cluster, administered by the Center for Theory and Computation.</p>

Impact Modeling for the Double Asteroid Redirection Test Mission

2019 ◽  
Author(s):  
Emma S.G. Rainey ◽  
Angela M. Stickle ◽  
Andrew F. Cheng ◽  
Andrew S. Rivkin ◽  
Nancy L. Chabot ◽  
...  
Keyword(s):  
Period Change ◽  
Full Scale ◽  
Full Scale Test ◽  
Binary Asteroid ◽  
Asteroid Impact ◽  
Planetary Defense ◽  
Asteroid Deflection ◽  
Post Impact ◽  
Scale Test ◽  
Binary Asteroid System

Abstract The Asteroid Impact Deflection Assessment (AIDA) collaboration is a joint ESA-NASA planetary defense collaboration that will include the first full-scale test of an asteroid deflection by kinetic impactor [1]. The AIDA collaboration comprises two independent spacecraft, the NASA-sponsored Double Asteroid Redirection Test (DART) and the ESA-led Hera. In September 2022 the DART spacecraft will impact the secondary member of the binary asteroid system 65803 Didymos (Didymos-B) at a speed of ~6.7 km/s and mass ~500 kg. The resulting period change in the orbit of Didymos-B will be measured using Earth-based observations. Hera will arrive post-impact and perform detailed measurements to characterize Didymos-B.

LICIACube observation capabilities of dust plume evolution after DART impact

2020 ◽  
Author(s):  
Vincenzo Corte ◽  
Elena Mazzotta Epifani ◽  
Elisabetta Dotto ◽  
Marilena Amoroso ◽  
Simone Pirrotta ◽  
...  
Keyword(s):  
Momentum Transfer ◽  
Transfer Efficiency ◽  
Mission Design ◽  
Binary Asteroid ◽  
Space Agency ◽  
Asteroid Deflection ◽  
High Resolution Images ◽  
Binary Asteroid System ◽  
Italian Space Agency ◽  
The Impact

<p>The NASA Double Asteroid Redirection Test (DART) mission will be the first test to check an asteroid deflection by a kinetic impactor. The target of DART mission is the secondary element of the (65803) Didymos binary asteroid system and the impact is expected in late September – early October, 2022. The DART S/C will carry a 6U cubesat called LICIACube (Light Italian Cubesat for Imaging of Asteroid), provided by the Italian Space Agency, with the aim to collect pictures of the impact’s effects. The impact of the 610 kg DART spacecraft at 6.58 km/s on the 163 m Didymos B will result in a change of the binary orbital period of about 10 minutes assuming momentum transfer efficiency β = 1. Values of β > 1 are expected because the produced ejecta carries momentum, primarily in the direction opposite the DART speed direction. The LICIACube mission profile consists in a flyby of Didymos system with closest approach about 3 minutes after the DART impact. LICIACube will be able to acquire the structure and evolution of the DART impact ejecta plume and will obtain high-resolution images and also in 3 colour of the surfaces of both bodies. The nominal mission foresees also imaging of the Dydymos B non-impact hemisphere. The contributions of LICIACube observations to the DART investigations are important for determination of the momentum transfer efficiency β, that is a crucial result of the planetary defence test. Moreover, captured images can enable scientific investigations about the main features of the asteroid system. </p><p>In order to check the imaging capability and to optimize the fast scientific phase of LICIAcube, the LICIA team performed several simulations of pictures’ acquisition. In these simulations, considering the specifications of the 2 optical payloads and the foreseen mission design, we reconstructed synthetic images mainly of the plume. As the plume evolution remains the most important uncertainty, since it depends on a very high number of impacting phase parameters, we simulated imaging of different expected evolution behaviours, to obtain instrument operative parameters and to prepare the data analysis.  </p>

scholarly journals Time-Resolved Spectroscopy of Accretion Disks in Algols

1989 ◽  
Vol 107 ◽  
pp. 51-61 ◽  
Author(s):  
Ronald H. Kaitchuck
Keyword(s):  
Emission Line ◽  
Accretion Disks ◽  
Velocity Fields ◽  
Continuum Emission ◽  
Turbulent Structures ◽  
Time Resolved ◽  
Time Resolved Spectroscopy ◽  
Long Period ◽  
Short Period ◽  
The Impact

AbstractTime-resolved spectroscopy during the eclipse of short-period Algol systems, has shown their accretion disks to be small, turbulent structures with non-Keplerian velocity fields and asymmetries between the leading and trailing sides of the disk. These transient disks are produced by the impact of the gas stream on the mass-gaining star, and occur in systems where the star is just large enough to ensure the stream collision is complete. These emission line disks and the excess continuum emission do not always occur together. The permanent accretion disks in at least a few of the long-period Algol systems have features in common with the transient disks including non-Keplerian velocity fields.

scholarly journals Freezing: how do water mites (Acari: Hydrachnidia) survive exposure to sub-zero temperatures?

2021 ◽  
Author(s):  
Andrzej Zawal ◽  
Tomasz Czernicki ◽  
Grzegorz Michoński ◽  
Aleksandra Bańkowska ◽  
Robert Stryjecki ◽  
...  
Keyword(s):  
Survival Rate ◽  
Survival Rates ◽  
Living Environment ◽  
Individual Species ◽  
Water Mites ◽  
Climatic Zones ◽  
Long Period ◽  
Short Period ◽  
The Moment ◽  
The Impact

AbstractUntil now, very little is known about the ability of adult and deutonymph water mites (Acari, Hydrachnidia) to survive in sub-zero temperatures. Information concerns mainly water mites from vernal astatic waters, and the knowledge has never been experimentally verified. To determine the sensitivity of water mites to freezing, experiments were conducted on (1) the impact of acclimatization, (2) temperature, and (3) duration of freezing on survival, (4) the survival rate of water mites from various types of water bodies, and (5) the survival rate of water mites from different climatic zones. The experiments were carried out in a phytotron chamber, and water mites were placed in containers (10 × 10 × 5 cm) filled with 4/5 of water for 10 specimens each. Water mites were identified to the species level after finishing the experiments. The temperature was lowered 1 °C every hour until the target temperature was reached. After a certain period of freezing (depending on the treatment) the temperature was raised by 1 °C every hour until it reached 4 °C. The time of the experiment was measured from the moment the desired temperature was reached (below 0 °C) until the ice thawed and the temperature of 4 °C was reached again. The highest survival rates had Limnochares aquatica, Piona nodata, Sperchon clupeifer and Lebertia porosa, followed by L. insignis, Hygrobates longipalpis, H. setosus, Limnesia undulatoides, Piona pusilla, Arrenurus globator, Hydrodroma despiciens, Piona longipalpis, Sperchonopsis verrucosa, Unionicola crassipes and Mideopsis crassipes; no specimens of Torrenticola amplexa survived. The following conclusions were drawn: (1) water mites can survive freezing to −2 °C, lower temperatures are lethal for them; (2) they survived better the short period of freezing (24–48 h) than the long period (168 h); (3) resistance to freezing seems to be an evolutionary trait of individual species, only partly related to the living environment; and (4) freezing survival rates are linked to the region of Europe and are much lower in Southern than in Central Europe.

LICIACube: Italian deep space small satellite technology for the Asteroid Redirection Test (DART) mission

2020 ◽  
Author(s):  
Simone Simonetti ◽  
Simone Pirrotta ◽  
Marilena Amoroso ◽  
Simone Pizzurro ◽  
Gabriele Impresario ◽  
...  
Keyword(s):  
Autonomous Navigation ◽  
Relative Velocity ◽  
Scientific Community ◽  
Space Mission ◽  
Binary Asteroid ◽  
Navigation Algorithm ◽  
Space Agency ◽  
Binary Asteroid System ◽  
Italian Space Agency ◽  
The Impact

<p>The Double Asteroid Redirection Test (DART) mission is part of the plan developed by NASA for the Planetary Defence program, since space mission towards asteroid have become crucial to study their composition. Moreover, these missions are the future of space exploration, providing opportunities for testing novel technologies for extreme conditions. These are some of the many reasons why NASA developed the Double Asteroid Redirection Test (DART) mission and the Italian Space Agency joined the effort. DART is a spacecraft acting as a kinetic impactor that will deflect the orbit of a binary asteroid by crashing itself into the moonlet of the Didymos binary system. In order to increase the accuracy of the deflection measurement, the ASI 6U Light Italian CubeSat for Imaging of Asteroid (LICIACube) will be carried on DART and released by the main probe in proximity of the target. The effects of the impact will be observed also from ground-based telescopes. The small satellite that will be the only witness of this event, LICIACube, is an Italian Space Agency project, and has been designed, integrated and tested by the assigned aerospace company Argotec. The primary objective of LICIACube is to capture photographs of DART impact ejecta plume over a span of times and phase angles in order to confirm the DART impact on the secondary body of the Didymos binary asteroid system and to observe the ejecta plume dynamics. After the deployment from the DART spacecraft, LICIACube will perform braking manoeuvers, to increase the relative velocity with respect to DART spacecraft, allowing LICIACube to perform the scientific phase and fulfil the mission objectives. Following this phase, the LICIACube satellite will continue on its path for few months, transferring scientific data and performing radio-science experiments. Many of the scientific objectives will be accomplished by using the autonomous navigation algorithm and the imaging capabilities provided by the baseline platform, based on the heritage of the Argotec company. The images acquired by LICIACube will help the Italian involved scientific community to obtain relevant discoveries about the binary asteroid system.</p> <p>The mission is articulated in a series of single critical moments: LICIACube will be deployed by DART 120 hours before the impact on Didymos B; the satellite will fly-by the asteroid with a relative velocity of 6.5 km/s, and it will document the effects of the impact, the crater and the evolution of the plume generated by the collision. To acquire images with the best spatial resolution, LICIACube will aim at fly-bying the asteroid close to the Didymos-B surface: considering the high relative velocity at the close approach, LICIACube will have to maintain the asteroid's pointing at an angular speed of approximately 10 deg/s. Scientific objectives will be accomplished by using the autonomous navigation algorithm and the imaging capabilities provided by the platform, based on the heritage of the Argotec company. The two optical payloads embarked on LICIACube have the duty of acquiring the images that are then processed on board through the navigation algorithm, thus allowing to identify the asteroid system, distinguish the main and secondary bodies and control the satellite attitude in order to keep the asteroid pointing during fly-by. The navigation algorithm is mainly based on neural network trained on ground using photorealistic images of the binary asteroid system and the plume generated by the impact.</p> <p>The images acquired and downlinked by the LICIACube satellite will help the scientific community to obtain more detailed results about the binary asteroid, and provide feedback to the Planetary Defense program, pioneered by the Space Agencies. The scientific team is enriched by University of Bologna team, supporting the orbit determination and the satellite navigation, Polytechnic of Milan, for mission analysis support and optimization and INAF (National Institute of Astrophysics), providing support in the scientific operations of the satellite. The LICIACube mission will be a challenging opportunity for the entire Italian technical and scientific community leading to the implementation of a deep space mission based on a small scale but highly technological platform.</p>

On nearly-commensurable periods in the restricted problem of three bodies, with calculations of the long-period variations in the interior 2:1 case

1966 ◽  
Vol 25 ◽  
pp. 197-222 ◽  
Author(s):  
P. J. Message
Keyword(s):  
Periodic Solution ◽  
Periodic Solutions ◽  
Large Amplitude ◽  
Restricted Problem ◽  
Small Amplitude ◽  
Minor Planets ◽  
Long Period ◽  
Numerical Integrations ◽  
Period Variations ◽  
The Mean

An analytical discussion of that case of motion in the restricted problem, in which the mean motions of the infinitesimal, and smaller-massed, bodies about the larger one are nearly in the ratio of two small integers displays the existence of a series of periodic solutions which, for commensurabilities of the typep+ 1:p, includes solutions of Poincaré'sdeuxième sortewhen the commensurability is very close, and of thepremière sortewhen it is less close. A linear treatment of the long-period variations of the elements, valid for motions in which the elements remain close to a particular periodic solution of this type, shows the continuity of near-commensurable motion with other motion, and some of the properties of long-period librations of small amplitude.To extend the investigation to other types of motion near commensurability, numerical integrations of the equations for the long-period variations of the elements were carried out for the 2:1 interior case (of which the planet 108 “Hecuba” is an example) to survey those motions in which the eccentricity takes values less than 0·1. An investigation of the effect of the large amplitude perturbations near commensurability on a distribution of minor planets, which is originally uniform over mean motion, shows a “draining off” effect from the vicinity of exact commensurability of a magnitude large enough to account for the observed gap in the distribution at the 2:1 commensurability.

Discussion following the presentation by F. Deubner

1977 ◽  
Vol 36 ◽  
pp. 69-74
Keyword(s):  
List Type ◽  
The Sun ◽  
Type Number ◽  
Harmonic Motion ◽  
Locally Excited ◽  
Long Period ◽  
Coherent Wave ◽  
Short Period ◽  
Global Modes

The discussion was separated into 3 different topics according to the separation made by the reviewer between the different periods of waves observed in the sun :1) global modes (long period oscillations) with predominantly radial harmonic motion.2) modes with large coherent - wave systems but not necessarily global excitation (300 s oscillation).3) locally excited - short period waves.

HBOT Application at Cases of Gingival Inflammation

2019 ◽  
Author(s):  
Ilma Robo
Keyword(s):  
Root Resorption ◽  
Periodontal Diseases ◽  
Therapeutic Effects ◽  
Clinical Effects ◽  
Gingival Inflammation ◽  
Beneficial Effects ◽  
New Therapeutic Approaches ◽  
Short Period ◽  
Mechanical Therapy ◽  
The Impact

The treatment of periodontal diseases, mainly of their origin, with the most common clinical manifestation in form of gingival inflammation, is manifold and powerful, including: mechanical therapy, antibiotic, antiseptic and various approaches to treatment, which are recommended to be used within a short period of time. New therapeutic approaches have been proven as alternative treatment to conventional therapy, or in combination with conventional therapies, to reduce the number of periodontopathic pathogens in gingival sulcus. HBOT has a detrimental effect on periodontal microorganisms, as well as beneficial effects on the healing of periodontal tissue, increasing oxygen pressure in gingival pockets. Our study is aimed at reviewing the current published literature on hyperbaric oxygen therapy and focuses on role of HBOT as a therapeutic measure for the individual with periodontal disease in general and for the impact on the recovery of gingival inflammation. HBOT and periodontal treatment together, reduce up to 99% of the gram-negative anaerobic load of subgingival flora. HBOT, significantly reduces subgingival anaerobic flora. Clinical effects in 2-year follow-up of treated patients are sensitive. Reduction of gingival hemorrhage indexes, depth of peritoneum, plaque index, occurs in cases of combination of HBOT and detraction. Reduced load persists up to 2 months after therapy. The significant increase in connective tissue removal starts at the end of 2nd week, to achieve the maximum in week 3-6 of application. HBOT used for re-implantation, stimulates the healing of periodontal membrane, pulp, prevents root resorption, healing of periodontal lining tissues. HBOT, significantly reduces the hemorrhage index with 1.2 value difference, 0.7mm probe depth, reduces gingival fluid by 2. HGH exposure is increased by gingival blood flow, with a difference of 2 in measured value. The therapeutic effects of HBOT in the value of the evaluation index can be saved up to 1-year post treatment.

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