Conference summary: Meteoroids

This paper gives the results of a debris and meteor oid flux analysis for satellites on different orbits. The goal is to combine a particle impact risk analysis with an estimation of the penetration probability for selected wall de signs. The impact probability is a result of the flux of debris objects on a certain o rbit and the meteoroid background flux. For the determination of the orbital debris flux, t he European MASTER (Meteoroid and Space Debris Terrestrial Environment Reference) model is used. The latest version of the model, MASTER-2005, was developed by a consortium under ESA/ESOC (European Space Operation Centre) contract. The consortium was led by the Institute of Aerospace Systems of the Technische Universitat Braunschweig (Germany). MASTER- 2005 was developed in cooperation with QinetiQ (UK), supported by Forschungsgesellschaft fur Angewandte Naturwissenschaften FGAN (Germany) and Astronomisches Institut Universitat Bern AIUB (Switzerland). MASTER-2005 is based on a validated debris population, considering all p articles on Earth orbits with diameters greater than 1 µm. The model considers all relevant sources like fragments, sodium-potassium (NaK) droplets, solid rocket motor (SRM) slag particles and Al 2O3 dust, ejecta, paint flakes and natural meteoroids. Impacts of space debris objects can damage satellites. Penetrating particles can cause failures or even the loss of a spacecraft. To prevent damages, it is useful to pro tect the satellite against particle impacts. In this case it is necessary to modify the satellite wall. To control the number of penetrations it may be useful to vary the spacing b etween the sheets of the honeycomb structure of the satellite hull. Using ballistic li mit equations, the minimum penetrating projectile diameter can be calculated. If the spaci ng is increased, the number of penetrations is significantly reduced. In GEO the n umber of impacts and penetrations is much lower than in LEO. The results are presented in terms of number of impacts and penetrations per area and year.

The currently proposed space debris remediation measures include the active removal of large objects and “just in time” collision avoidance by deviating the objects using, e.g., ground-based lasers. These techniques require precise knowledge of the attitude state and state changes of the target objects. In the former case, e.g. to devise methods to capture the target with a tug spacecraft, in the latter, to precisely propagate the orbits of potential collision partners, as disturbing forces like air drag and solar radiation pressure depend on the attitude of the objects. The long-term evolution of the attitude motion is, among many other causes, depending on the effects of possible im- pacts of debris and meteoroid, while momentum transfer from reaction wheels or other moving internal components may contribute to the root cause of the initial attitude motion. Impacts of small particles like meteoroids and space debris pieces on compact space objects are unavoidable events, which were already observed several times, e.g., on International Space Station, or rather recently on the Sentinel-1A on August 23, 2016. This paper will discuss a detailed analysis of the effects of momentum transfer from the reaction wheels and of debris and meteoroid impacts for the particular case of Envisat. Based on the physical model of Envisat and the MASTER environment model, the likelihood to have an impact-related attitude rate increase in ten years larger than selected threshold rates was determined.

Meteoroids' effect studied

Evolution of Halley-type Comets and Meteoroid Streams

Diffusion of long-period orbits for comets and meteoroid streams

Conference on Meteoroids 1994 August 28–31 Bratislava, Slovakia

Hypervelocity impact of meteoroids and orbital debris poses a serious and growing threat to spacecraft. To study hypervelocity impact phenomena, a comprehensive ensemble of real-time concurrently operated diagnostics has been developed and implemented in the Small Particle Hypervelocity Impact Range (SPHIR) facility. This suite of simultaneously operated instrumentation provides multiple complementary measurements that facilitate the characterization of many impact phenomena in a single experiment. The investigation of hypervelocity impact phenomena described in this work focuses on normal impacts of 1.8 mm nylon 6/6 cylinder projectiles and variable thickness aluminum targets. The SPHIR facility two-stage light-gas gun is capable of routinely launching 5.5 mg nylon impactors to speeds of 5 to 7 km/s. Refinement of legacy SPHIR operation procedures and the investigation of first-stage pressure have improved the velocity performance of the facility, resulting in an increase in average impact velocity of at least 0.57 km/s. Results for the perforation area indicate the considered range of target thicknesses represent multiple regimes describing the non-monotonic scaling of target perforation with decreasing target thickness. The laser side-lighting (LSL) system has been developed to provide ultra-high-speed shadowgraph images of the impact event. This novel optical technique is demonstrated to characterize the propagation velocity and two-dimensional optical density of impact-generated debris clouds. Additionally, a debris capture system is located behind the target during every experiment to provide complementary information regarding the trajectory distribution and penetration depth of individual debris particles. The utilization of a coherent, collimated illumination source in the LSL system facilitates the simultaneous measurement of impact phenomena with near-IR and UV-vis spectrograph systems. Comparison of LSL images to concurrent IR results indicates two distinctly different phenomena. A high-speed, pressure-dependent IR-emitting cloud is observed in experiments to expand at velocities much higher than the debris and ejecta phenomena observed using the LSL system. In double-plate target configurations, this phenomena is observed to interact with the rear-wall several micro-seconds before the subsequent arrival of the debris cloud. Additionally, dimensional analysis presented by Whitham for blast waves is shown to describe the pressure-dependent radial expansion of the observed IR-emitting phenomena. Although this work focuses on a single hypervelocity impact configuration, the diagnostic capabilities and techniques described can be used with a wide variety of impactors, materials, and geometries to investigate any number of engineering and scientific problems.

Question 1: The dinosaur meteoroid and the day; Question 2: School guards

This chapter briefl y discusses the process in which a meteoroid in space encounters Earth’s atmosphere and becomes visible as a meteor. Should the meteor survive the plunge through the atmosphere it then encounters Earth’s surface as a meteorite.

Classes of Meteorites

Evidence for Ice Meteoroids Beyond 2 AU

Saturn's Meteoroid Crash

Meteoroids to Meteorites: Lessons in Survival

Grazing meteoroids could ignite continental-scale fires

In the fall of 1798, University of Göttingen students Johann Friedrich Benzenberg and Heinrich Wilhelm Brandes set out to prove new ideas about the nature of meteors. In 1714, Edmund Halley had challenged Aristotle by suggesting that fireballs are not slow burning terrestrial vapors but solid objects entering Earth's atmosphere at high speed, only later to rescind. Ernst Chladni first reasoned that opinion most convincingly in 1794.