Box-of-Rocks Experiment II: Testing Magnetic Sampling and Grappling on Small Asteroids

Planetary and Space Science, 2014

Surface properties of small asteroids are reviewed in this work focusing on microgravity related processes in order to give constrains for targeting sample acquisition by next missions, especially for MarcoPolo-R proposed by ESA. Based on our current knowledge and the planned capabilities of this mission, good chance exists to get answers for the following basic questions. Formation method of nanophase iron and amorphous ingredients in the regolith could be determined, surface particle size and regolith density estimation would also be gained, and with extrapolation to the rest of the surface, knowledge on transport processes, ages and results of cratering under special gravity-strength regime will be improved. Searching for fresh material on asteroid surface in general requires sophisticated effort, as small craters often do not produce much ejecta in microgravity, but the bright annuli around them could be the result of local surface disturbance, while slopes often exhibit fresh material. To identify these locations high albedo, bluer colour and occasionally the depth of 1 μm absorption band could be useful as they often change parallel to each other. To identify the best area for sample acquisition addresses a strategic question: while smooth terrains with easy navigation and sample acquisition provide strongly weathered fine grains; steeper terrains give access to less weathered, material more representative for the whole asteroid, but navigation and mechanical sampling rise difficulties there.

AstEx is a microgravity experiment selected to fly on ESA's 51st Microgravity Research Campaign in November 2009. The experiment will investigate the dynamics of regolith on asteroid surfaces. Despite their very low surface gravities, asteroids exhibit a number of different geological processes involving granular matter. Understanding the mechanical response of this granular material subject to external forces in microgravity conditions is vital to the design of a successful asteroid sub-surface sampling mechanism, and in the interpretation of the fascinating geology on an asteroid. The AstEx experiment uses a microgravity modified Taylor-Couette shear cell to investigate granular flow caused by shear forces under the conditions of parabolic flight microgravity. It is intended to determine how a steady state granular flow is achieved in microgravity conditions, and what effect prior shear history has on the timescales involved in initiating a steady state flow in a granular material. Presented are the technical details of the AstEx experimental design with particular emphasis on how the team have designed the equipment specifically for the parabolic flight microgravity environment.

The regolith-covered surfaces of asteroids preserve records of geophysical processes that have occurred both at their surfaces and sometimes also in their interiors. As a result of the unique micro-gravity environment that these bodies posses, a complex and varied geophysics has given birth to fascinating features that we are just now beginning to understand. The processes that formed such features were first hypothesised through detailed spacecraft observations and have been further studied using theoretical, numerical and experimental methods that often combine several scientific disciplines. These multiple approaches are now merging towards a further understanding of the geophysical states of the surfaces of asteroids. In this chapter we provide a concise summary of what the scientific community has learned so far about the surfaces of these small planetary bodies and the processes that have shaped them. We also discuss the state of the art in terms of experimental techniques and...

Acta Astronautica, 2011

This paper presents the results of a mission concept study for an autonomous microscale surface lander also referred to as PANIC -the Pico Autonomous Near-Earth Asteroid In Situ Characterizer. The lander is based on the shape of a regular tetrahedron with an edge length of 35 cm, has a total mass of approximately 12 kg and utilizes hopping as a locomotion mechanism in microgravity. PANIC houses four scientific instruments in its proposed baseline configuration which enable the in situ characterization of an asteroid. It is carried by an interplanetary probe to its target and released to the surface after rendezvous. Detailed estimates of all critical subsystem parameters were derived to demonstrate the feasibility of this concept. The study illustrates that a small, simple landing element is a viable alternative to complex traditional lander concepts, adding a significant science return to any near-Earth asteroid (NEA) mission while meeting tight mass budget constraints.

arXiv: Earth and Planetary Astrophysics, 2016

The aim of the Asteroid Science Intersections with In-Space Mine Engineering (ASIME) 2016 conference on September 21-22, 2016 in Luxembourg City was to provide an environment for the detailed discussion of the specific properties of asteroids, with the engineering needs of space missions that utilize asteroids. The ASIME 2016 Conference produced a layered record of discussions from the asteroid scientists and the asteroid miners to understand each other's key concerns and to address key scientific questions from the asteroid mining companies: Planetary Resources, Deep Space Industries and TransAstra. These Questions were the focus of the two day conference, were addressed by scientists inside and outside of the ASIME Conference and are the focus of this White Paper. The Questions from the asteroid mining companies have been sorted into the three asteroid science themes: 1) survey, 2) surface and 3) subsurface and 4) Other. The answers to those Questions have been provided by the...

This study is carried out in the framework of sample-return missions to asteroids that use a low-speed projectile as the primary component of its sampling mechanism (e.g., JAXA's Hayabusa and Hayabusa2 missions). We perform numerical simulations of such impacts into granular materials using different projectile shapes under Earth's gravity. We then compare the amounts of ejected mass obtained in our simulations against what was found in experiments that used similar setups, which allows us to validate our numerical approach. We then investigate the sensitivity of various parameters involved in the contacts between grains on the amount of mass that is ejected. * Corresponding author (Phone/Fax): +33 4 92 00 30 (55/58) the timescale of the impact process. A dedicated quantitative study in microgravity is the subject of future work. We also plan to study other aspects of the ejection process such as velocity distributions and crater properties, and to adapt our methodology to the conditions of sampling mechanisms included in specific mission designs.

Icarus, 1996

nary work on dust levitation on asteroids (Cheng 1995; Lee 1995a,b), however, little consideration has been given In comparison to the lunar regolith, asteroidal regoliths appear to be deficient in dust and in agglutinates, i.e., in particles to electrostatic processes at the surface of asteroids. Yet, Յ100 m across. On asteroid surfaces of high electrical resistivbecause of the low-gravity environment on asteroids and ity, such particles may be electrostatically levitated and the the presence of regoliths on many, electrostatic processes smaller size fraction may be preferentially lost. Two electrocould have a significant effect on determining their surface static field production mechanisms commonly considered for properties. In the present study, it is suggested that strong the Moon, where dust levitation has been repeatedly observed, electrostatic fields can develop on electrically resistive asare applied to asteroids. Fields generated by electron phototeroids and might contribute to winnowing their regolith emission appear effective in levitating charged grains. As a of their finest particle size fraction. After a review of dust surface element on a resistive asteroid rotates into and out of levitation on the Moon (Section 2), two mechanisms comview of the sun, electrostatic levitation winnows its uppermost monly proposed in the lunar context are applied to asterparticulate layer. Depending on the asteroid's size, rotation oids (Section 3). The first mechanism generates electrorate, heliocentric distance, and other factors, levitated fines up to ȁ10 ؊2 m in diameter may escape directly by electrostatic static fields on a global scale (cf. Manka 1973, Mendis et acceleration. Particles 10 ؊2 -1 m across lofted in the subescape al. 1981); the second produces fields locally, at the scale regime may also be entrained to escape by solar wind drag of surface asperities, along the terminator (cf. Criswell and radiation pressure. Larger levitated particles remaining 1973). The effectiveness of each mechanism when applied gravitationally bound to the asteroid (Ն1-100 m) are redisto asteroids is assessed. Under specific but unextraordinary tributed across its surface following local electrostatic and gravcircumstances, charged regolithic fines are found to leviity gradients. Their migration is arrested when they settle in tate. In the terminator fields case, we show that it is critical topographic traps and/or in perennially shadowed areas (e.g., to compare the charging timescale against the timescale for craters, grooves). Electrostatic levitation may be an effective terminator crossing, the latter varying considerably with process of fine particle segregation and transport on asteroids, asteroid size, rotation rate and pole orientation (Section and might constitute a significant loss mechanism for their smallest particle size fraction during time intervals between 4). The ultimate fate of levitated grains is a function of large, regolith-dispersing impacts. The process may also contheir charge and size. On a 20 km-radius resistive asteroid tribute to forming coarse-grained near-surface charged ''dustat 3 AU, particles up to 10 Ϫ2 Ȑm across may be electrostatispheres'' over the sunlit hemispheres of some asteroids. Possible cally accelerated to escape. Of the coarser particles that evidence for fine particle levitation on various asteroids is are levitated in the subescape regime, those Յ1 Ȑm across discussed.

Advances in Space Research, 2009

We present a concept for a challenging in situ science mission to a primitive, binary near-Earth asteroid. A sub-400-kg spacecraft would use solar electric propulsion to rendezvous with the C-class binary asteroid (175706) 1996 FG3. A campaign of remote observations of both worlds would be followed by landing on the $1 km diameter primary to perform in situ measurements. The total available payload mass would be around 34 kg, allowing a wide range of measurement objectives to be addressed. This mission arose during 2004 from the activities of the ad-hoc Small Bodies Group of the DLR-led Planetary Lander Initiative. Although the particular mission scenario proposed here was not studied further per se, the experience was carried over to subsequent European asteroid mission studies, including first LEONARD and now the Marco Polo near-Earth asteroid sample return proposal for ESA's Cosmic Vision programme. This paper may thus be of interest as much for insight into the life cycle of mission proposals as for the concept itself.

Advances in Space Research

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The magnetometer investigation aboard the NEAR-Shoemaker spacecraft has obtained extensive magnetic field observations throughout the 433 Eros environment, from distances in excess of 100,000 km to those conducted after landing on 12 February 2001. We report the apparent absence of global scale magnetization at this asteroid (H < 0.005 A (.) m(-1); natural remanent magnetization per kilogram < 1.9 x 10(-6) A (.) m(2) (.) kg(-1)), orders of magnitude less than the intense magnetization attributed to S-class asteroids Gaspra and Braille. The extremely low magnetization state of 433 Eros places this object significantly below the levels generally associated with LL chondrites and undifferentiated primitive bodies, challenging our current understanding of the meteorite-asteroid connection.