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NASA NTRS2019

Outgassing From the OSIRIS-REx Sample Return Capsule: Characterization and Mitigation

The Origins, Spectral Interpretation, Resource Identification, and Security–Regolith Explorer (OSIRIS-REx) spacecraft launched on September 8, 2016, beginning a seven-year journey to return at least 60 g of asteroid material from (101955) Bennu to Earth. During the outboundcruise, Doppler tracking of the spacecraft observed a small but measurable acceleration when the sample return capsule (SRC) was first placed in sunlight. Subsequent analysis determined that outgassing from the SRC is the most likely cause for the acceleration. This outgassing received combined engineering and scientific attention because it has potential implications both for spacecraft navigation performance and for contamination of the collected samples. Thermal modeling, laboratory studies of SRC materials, and monitoring of the acceleration are all consistent with H2O as the main component of the outgassing. Dedicated, in-flight campaigns continued to expose the SRC to sunlight until the acceleration dropped to the acceleration noise floor. Any residual amounts of H2O outgassing are not considered to be a hazard with regards to mission operations or pristine sample acquisition. The sample stow procedure has been updated to ensure that no direct line of site exists between any residual outgassing and the samples during future operations. Similar outgassing of the Stardust SRC probably also occurred. No adverse contamination of Stardust samples was observed that could be associated with this process. Future missions that use similar reentry vehicles should consider procedures to test for and, if necessary, mediate such outgassing after launch.

Scott A Sandford↗

NASA NTRSDate not supplied

The Unique Scientific Value of Returned Samples

Most of the materials in the universe are so distant or inaccessible that the only way we can study them is remotely using various types of telescopes. However, in some cases we can study these materials directly because the samples become physically available to us. Some samples come to us of their own accord in the form of meteorites and cosmic dust. In other cases we have to work hard to carry out sample return missions like Apollo, Stardust, OSIRIS-REx, Hayabusa, and Hayabusa2 in order to get the samples ourselves. Once samples are physically available in terrestrial laboratories, we can learn details about their compositions and histories that could never be established by remote observations. This talk will highlight some of the unique scientific advances that can be made through the study of extraterrestrial materials, and will describe the various ways in which samples become available for study, with a focus on the acquisition of samples by sample return spacecraft missions. Aspects of NASA’s Stardust comet sample return mission and JAXA’s Hayabusa asteroid sample return mission will be highlighted and scientific highlights of these missions will be discussed. Finally, the presentation will end with an overview of the current status of NASA’s OSIRIS-Rex mission, which will is currently at Asteroid (101955) Bennu and will be returning samples to Earth in 2023.

Extraterrestrial Samples↗

NASA NTRS2024

Chemical and Physical Properties of Cometary Dust

Cometary dust particles are best preserved remnants of the matter present at the onset of the formation of the Solar System. In Space missions, telescopic observations and laboratory analyses advanced the knowledge on the properties of cometary dust. the only samples certified with a cometary origin were returned by the Stardust space mission from comet 81P/Wild2. The “chondritic porous” (here called “chondritic anhydrous”) interplanetary dust particles (CA-IDPs) and micrometeorites (CP-MMs), and the ultracarbonaceous Antarctic MMs (UCAMMs) also show strong evidence for a cometary origin. The elemental composition of cometary dust is generally consistent with the chondritic (CI) composition, with the notable exception of elevated contents in carbon and nitrogen compared with CI. The organic matter of cometary dust is mixed with minor amounts of crystalline (at least 25% of the minerals) and amorphous mineral phases. The most abundant crystalline minerals are ferromagnesian silicates (olivine and low-Ca pyroxenes), but High-Ca pyroxenes, refractory minerals and Low Ni Fe sulfides are also present. The crystalline olivine and low-Ca pyroxene compositions can vary from their Mg-rich end-member (forsterite and enstatite) to relatively Fe-rich compositions. Refractory minerals as well as secondary minerals likeLIME (low-iron, Mn-enriched) olivines, unusual Fe sulfides or mineral aggregates of specific compositions like Kosmochloric high-Ca pyroxene and FeO-rich olivine - KOOL grains) are also found. The presence of carbonates in cometary dust is still debated, but a phyllosilicate-like phase was observed in a UCAMM. The abundance of pyroxene to olivine (in numbers) is larger than in primitive meteorites (e.g. the Px/Ol ratio is usually larger than 1). GEMS phases (glass with embedded metals and sulfides) are abundant in cometary dust, although not systematically found. Some of the organic matter present in cometary dust particle resembles the insoluble organic matter (IOM) present in primitive meteorites, but amorphous carbon and exotic (e.g. N-rich) organic phases are also present. The hydrogen isotopic composition of cometary dust particles (in the organic matter) is usually rich in deuterium, tracing a formation at very low temperatures, either in the protosolar cloud or in the outer regions of the protoplanetary disk. The presolar dust concentration in cometary dust can reach about 1%, which is the most elevated value observed in extraterrestrial samples. The size distribution of cometary dust in comet trails is well represented by a power-law distribution (differential size distribution) with a mean power index N typically ranging from -3 to -4. Polarimetric and light scattering studies of cometary dust suggest mixtures of porous agglomerates of sub-micrometer minerals with organic matter, which is compatible with the in situ analyses of 67P/Churyumov-Gerasimenko by MIDAS (Rosetta) and with the studies of it Stardust samples, CA-IDPs, CP-MMs and UCAMMs. Cometary dust particles have low tensile strength, and low density.

C. Engrand↗

NASA NTRSDate not supplied

Applicability of Micro X-Ray Fluorescence Spectroscopy to Astromaterials Curation and Research

Introduction: The Astromaterials Acquisition and Curation Office at NASA’s Johnson Space Center (JSC) curates NASA’s astromaterial sample collections which includes: Apollo samples, Luna samples, Ant-arctic meteorites, cosmic dust particles, microparticle impacts into space-flown materials, Genesis solar wind atoms, Stardust comet Wild-2 particles, Stardust inter-stellar particles, Hayabusa asteroid Itokawa particles, Hayabusa 2 asteroid Ryugu particles, and future OSIRIS-Rex asteroid Bennu particles (landing in Sep-tember, 2023) [1–3]. To enhance JSC’s advanced cu-ration capabilities, we have recently installed a high-performance micro-X-ray fluorescence (µXRF) spec-trometer to assist in sample characterization through rapid, non-destructive, in-situ elemental analyses that do not require the sample preparation protocols (i.e., polishing and carbon-coating) commonly needed for electron beam analyses. With this new instrument, we are capable of detecting all elements down to carbon in a variable-pressure or He-purged chamber for anal-ysis of a wide range of sample types. Here we describe the instrumental set-up, capabilities, and applicability of µXRF analysis to astromaterials curation and re-search. Instrumentation and Methodology: The X-ray fluorescence and computed tomography lab (X-FaCT) lab at JSC is now equipped with a Bruker M4 Tornado Plus µXRF (Fig. 1). This system is an energy-dispersive x-ray spectrometer equipped with two 60 mm2 silicon drift detectors (SDD) that are able to be used simulta-neously for output count rates ~500,000 cps. New light element windows allow detecting and analyzing the entire elemental range from carbon to americium. Two x-ray tubes (micro-focus Rh with polycapillary lenses and W with collimators of 0.5, 1.0, 2.0, and 4.5 mm) with max excitation parameters of 50 kV, 30 W and 50 kV, 40 W, respectively, allow for more flexibility of the analysis of high energy lines. The motorized X-Y-Z stage has a mapping range of 190 x 160 mm and can support samples up to 7 kg (~15.5 lbs) and a height of 120 mm [4]. Analytical modes include elemental analysis (down to ~20 µm spot size) via point, line, or area of bulk materials (rock surfaces, thin sections, thick sections, etc.) as well as coating analysis (determination of thickness and composition) of samples. This system has a variable vacuum chamber (1 mbar to 1 atm) that is also equipped with a He-purge system which accommodates vacuum sensitive samples while still allowing detection of light elements at atmospheric pressure. Utility and Applicability of µXRF in Astro-materials research and exploration science (ARES): Elemental analysis using µXRF is commonly em-ployed for both terrestrial and planetary geological science disciplines [5]. It is especially useful for analy-sis of astromaterials given the limited sample prepara-tion required, which is not feasible for certain materi-als. Here we show select applications of µXRF anal-yses of astromaterials that can, have, and will be done at JSC’s X-FaCT lab. Point analysis: In-situ spot analyses (~20 µm spot size) on a cut slab of Martian meteorite NWA 10922 allowed for the discovery, qualitative elemental analy-sis and determination of different feldspar minerals [6]. These point analyses served as an effective prelim-inary step for subsequent quantitative analyses. Ana-lytical standards can be employed for more accurate quantification of µXRF spot analyses. Area analysis: This analytical mode measures all detectable elements (from C to Am) at each pixel (>5 µm pixel size) in a user-defined area. The results are shown as elemental maps which can be extracted as 16-bit TIFF’s for further data processing. In Fig. 2. we show elemental distribution maps of the high-Ti basalt 73001,531 that have been processed using ImageJ software. From these maps you can accurately and quickly (this map took ~50 mins.) identify mineral components, such as pyroxene, plagioclase, oxides, and phosphates, compositional zoning, and mineral textures. Detection of high-Z phases: µXRF techniques are es-pecially effective at analyzing trace minerals with high-atomic-number (high-Z) elements because the high-energy characteristic X-rays used (relative to SEM EDS) allow for mapping of K lines in elements up to La (typically SEM maps use L X-ray lines for elements >Zn, and these can often have interferences). Thus, µXRF is especially suited for identifying minerals like zircon, baddeleyite, REE-rich phosphates, Fe-rich met-als, oxides, sulfides, and phosphides [4]. In Fig. 3 we show elemental distribution maps for 73001,530 where we are able to correlate the original video image with, Zr, Si, Y and Hf elemental maps together identi-fying the location of a zircon. In this location you would expect lower Si compared to surrounding mate-rial, as well as higher Zr, Y, and Hf content compared to surrounding material, all of which is confirmed by our XRF ele-mental distribution maps (Figure 2.) Conclusions: The new M4 Tornado Plus µXRF within the Astromaterials Acquisition and Curation office at NASA JSC allows for rapid and non-destructive elemental analysis of astromaterials with limited or no sample preparation. µXRF analyses pro-vide crucial compositional knowledge for the prelimi-nary examination and curation of astromaterials. This instrument enhances the advanced curation capabili-ties in the X-FaCT laboratory at JSC by allowing pro-ductive, cohesive, and non-destructive multi-modal x-ray analyses on astromaterial samples, which is neces-sary for the comprehensive curation and study of our current and future astromaterial collections. Addition-ally, µXRF can provide complimentary information to researchers for studies on astromaterials. References: [1] Allen, C. et al., (2011). Chemie De Erde Geochemistry, 71, 1-20. [2] McCubbin, F. M. et al., (2016) 47th LPSC, abstract #2668 [3] Zeigler, R. A. et al., (2017) 48th LPSC, abstract #2772 [4] Bruker User Manual [5] Young et al., (2016) Appl. Geochemistry, 72, 77-87 [6] Mor-ris, R. V. et al., (2023) 54th LPSC.

E W O'Neal↗

NASA NTRS2020

An Evolutionary System of Mineralogy. Part I: Stellar Mineralogy (>13 to 4.6 Ga)

Minerals preserve records of the physical, chemical, and biological histories of their origins and subsequent alteration, and thus provide a vivid narrative of the evolution of Earth and other worlds through billions of years of cosmic history. Mineral properties, including trace and minor elements, ratios of isotopes, solid and fluid inclusions, external morphologies, and other idiosyncratic attributes, represent information that points to specific modes of formation and subsequent environmental histories—information essential to understanding the co-evolving geosphere and biosphere. This perspective suggests an opportunity to amplify the existing system of mineral classification, by which minerals are defined solely on idealized end-member chemical compositions and crystal structures. Here we present the first in a series of contributions to explore a complementary evolutionary system of mineralogy—a classification scheme that links mineral species to their paragenetic modes. The earliest stage of mineral evolution commenced with the appearance of the first crystals in the universe at >13 Ga and continues today in the expanding, cooling atmospheres of countless evolved stars, which host the high-temperature (T > 1000 K), low-pressure (P < 10-2 atm) condensation of refractory minerals and amorphous phases. Most stardust is thought to originate in three distinct processes in carbon- and/or oxygen-rich mineral-forming stars: (1) condensation in the cooling, expanding atmospheres of asymptotic giant branch stars; (2) during the catastrophic explosions of supernovae, most commonly core collapse (Type II) supernovae; and (3) classical novae explosions, the consequence of runaway fusion reactions at the surface of a binary white dwarf star. Each stellar environment imparts distinctive isotopic and trace element signatures to the micro- and nanoscale stardust grains that are recovered from meteorites and micrometeorites collected on Earth’s surface, by atmospheric sampling, and from asteroids and comets. Although our understanding of the diverse mineral-forming environments of stars is as yet incomplete, we present a preliminary catalog of 41 distinct natural kinds of stellar minerals, representing 22 official International Mineralogical Association (IMA) mineral species, as well as 2 as yet unapproved crystalline phases and 3 kinds of non-crystalline condensed phases not codified by the IMA.

Robert M. Hazen↗

NASA NTRSDate not supplied

Identification of Presolar Grains in Quick Look Samples of Asteroid Bennu Returned By the OSIRIS-REx Mission

The OSIRIS-REx spacecraft returned regolith sample from the B-type asteroid Bennu on September 24, 2023. The first samples to be analyzed, termed the Quick Look samples, are comprised of material collected from the avionics deck of the OSIRIS-REx sample canister. Initial mineralogical analysis of the Quick Look sample revealed a diversity of components, including hydrated and anhydrous silicates, sulfides, magnetite, phosphates, and abundant organic matter. Each constituent has their own origin and history, and their study can inform us of the history of Bennu and its parent asteroid. The analysis plan for asteroid Bennu samples is guided by hypotheses that address specific periods of Bennu’s history, from the pre-accretionary epoch to the OSIRIS-REx epoch. The pre-accretionary epoch studies aim to characterize materials that predate the formation of the solar system. One hypothesis that falls under this epoch is that Bennu contains presolar materials derived from diverse sources. These presolar materials include stardust grains that condensed from the outflows of evolved stars or the ejecta of novae and supernovae (SN), as well as organic matter that formed in the interstellar medium. Here we report the identification of C-rich presolar stardust grains in the Bennu Quick Look sample. Isotopically anomalous organic matter in this sample is reported in.

A N Nguyen↗

NASA NTRS2007

Sample Return Primer and Handbook

This three-part Sample Return Primer and Handbook provides a road map for conducting the terminal phase of a sample return mission. The main chapters describe element-by-element analyses and trade studies, as well as required operations plans, procedures, contingencies, interfaces, and corresponding documentation. Based on the experiences of the lead Stardust engineers, the topics include systems engineering (in particular range safety compliance), mission design and navigation, spacecraft hardware and entry, descent, and landing certification, flight and recovery operations, mission assurance and system safety, test and training, and the very important interactions with external support organizations (non-NASA tracking assets, landing site support, and science curation).

Stardust↗

NASA NTRS2015

Plume Collection Strategies for Icy World Sample Return

Three icy worlds in the solar system display evidence of pluming activity. Water vapor and ice particles emanate from cracks near the south pole of Saturn's moon Enceladus. The plume gas contains simple hydrocarbons that could be fragments of larger, more complex organics. More recently, observations using the Hubble and Herschel space telescopes have hinted at transient water vapor plumes at Jupiter's moon Europa and the dwarf planet Ceres. Plume materials may be ejected directly from possible sub-surface oceans, at least on Enceladus. In such oceans, liquid water, organics, and energy may co-exist, making these environments habitable. The venting of habitable ocean material into space provides a unique opportunity to capture this material during a relatively simple flyby mission and return it to Earth. Plume collection strategies should enable investigations of evidence for life in the returned samples via laboratory analyses of the structure, distribution, isotopic composition, and chirality of the chemical components (including biomolecules) of plume materials. Here, we discuss approaches for the collection of dust and volatiles during flybys through Enceladus' plume, based on Cassini results and lessons learned from the Stardust comet sample return mission. We also highlight areas where sample collector and containment technology development and testing may be needed for future plume sample return missions.

Stardust Collector↗

NASA NTRS2011

Risk Balance: A Key Tool for Mission Operations Assurance

The Mission Operations Assurance (MOA) discipline actively participates as a project member to achieve their common objective of full mission success while also providing an independent risk assessment to the Project Manager and Office of Safety and Mission Success staff. The cornerstone element of MOA is the independent assessment of the risks the project faces in executing its mission. Especially as the project approaches critical mission events, it becomes imperative to clearly identify and assess the risks the project faces. Quite often there are competing options for the project to select from in deciding how to execute the event. An example includes choices between proven but aging hardware components and unused but unproven components. Timing of the event with respect to visual or telecommunications visibility can be a consideration in the case of Earth reentry or hazardous maneuver events. It is in such situations that MOA is called upon for a risk balance assessment or risk trade study to support their recommendation to the Project Manager for a specific option to select. In the following paragraphs we consider two such assessments, one for the Stardust capsule Earth return and the other for the choice of telecommunications system configuration for the EPOXI flyby of the comet Hartley 2. We discuss the development of the trade space for each project's scenario and characterize the risks of each possible option. The risk characterization we consider includes a determination of the severity or consequence of each risk if realized and the likelihood of its occurrence. We then examine the assessment process to arrive at a MOA recommendation. Finally we review each flight project's decision process and the outcome of their decisions.

operations↗

NASA NTRS2008

VML Sequencing: Growing Capabilities over Multiple Missions

Virtual Machine Language (VML) is an award-winning advanced procedural sequencing language in use on NASA deep-space missions since 1997. Missions featuring VML include Spitzer Space Telescope, Mars Odyssey, Stardust, Genesis, Mars Reconnaissance Orbiter, Phoenix, Dawn and Juno. The latest deployed version, VML 2.0, features parameterized functions, conditionals, polymorphism, a rich set of control directives and data types, event detection and response, and on-the-fly creation of spacecraft commands. This feature set is used to simplify spacecraft operations and science gathering activities. A new 2.1 version is being prototyped for use as an executive within flight instruments, and may be deployed on Juno.

Dawn↗

NASA NTRS1983

Discovery of s-process Nd in Allende residue

New interpretation is given to the isotopic anomalies detected by Lugmair et al. (1983) in an acid-resistant residue of the Allende meteorite. If the Nd-142 excess is due to Sm-146 decay, as the discoverers proposed, it is argued that the decay has occurred in interstellar grains, so that the conclusion that Sm-146 (1.03 x 10 to the 8th yr) was alive in the solar system is premature. It is shown by renormalizing their data that the discovery is likely to be s-process Nd, confirming the survival of red-giant stardust in carbonaceous interstellar dust.

Clayton, D. D.↗

NASA NTRS1991

Astrophysical dust grains in stars, the interstellar medium, and the solar system

Studies of astrophysical dust grains in circumstellar shells, the interstellar medium, and the solar system may provide information about stellar evolution and about physical conditions in the primitive solar nebula. The following subject areas are covered: (1) the cycling of dust in stellar evolution and the formation of planetary systems; (2) astrophysical dust grains in circumstellar environments; (3) circumstellar grain formation and mass loss; (4) interstellar dust grains; (5) comet dust and the zodiacal cloud; (6) the survival of dust grains during stellar evolution; and (7) establishing connections between stardust and dust in the solar system.

Gehrz, Robert D.↗

NASA NTRS1992

Condensation of cosmic analog material in microgravity conditions - Preliminary analysis of a first set of flights

The first results of the STARDUST project, aimed at producing and analyzing cosmic-dust analog materials in microgravity conditions, are summarized. The discussion covers the purpose of the investigation, cosmic-dust formation and properties, previous simulations of cosmic-dust formation, the current approach, the microgravity experimental apparatus, and potential advantages of studying dust formation under microgravity conditions.

Mancini, D.↗

NASA NTRS1993

Classical novae - Contributions to the interstellar medium

Theoretical results predicting yields of various isotopes in nova outbursts are reviewed. Emphasis is placed on the stardust and gas-phase chemical anomalies that may be contributed to the Galactic ISM by classic novae. It is concluded that most of the heavy isotope anomalies are produced by about 25 percent of novae that occur in systems containing massive O-Ne-Mg white dwarfs. The dust-production scenario for novae is summarized, and it is argued that explosions on O-Ne-Mg white dwarfs may lead to the formation of dust grains that carry the Ne-E and Mg-26 anomalies. Quantitative constraints are placed on the degree to which classical novae participate in the production of chemical anomalies, both in the primitive solar system and on a Galactic scale.

Gehrz, Robert D.↗

NASA NTRS1993

Interstellar grains in primitive meteorites - Diamond, silicon carbide, and graphite

Primitive meteorites contain a few parts per million (ppm) of pristine interstellar grains that provide information on nuclear and chemical processes in stars. Their interstellar origin is proven by highly anomalous isotopic ratios, varying more than 1000-fold for elements such as C and N. Most grains isolated thus far are stable only under highly reducing conditions (C/O greater than 1), and apparently are 'stardust' formed in stellar atmospheres. Microdiamonds, of median size about 10 A, are most abundant (about 400-1800 ppm) but least understood. They contain anomalous noble gases including Xe-HL, which shows the signature of the r- and p-processes. Silicon carbide, of grain size 0.2-10 microns and abundance about 6 ppm, shows the signature of the s-process and apparently comes mainly from red giant carbon (AGB) stars of 1-3 solar masses. Some grains appear to be not less than 10 exp 9 a older than the solar system. Graphite spherules of grain size 0.8-7 microns and abundance less than 2 ppm contain highly anomalous C and noble gases, as well as large amounts of fossil Mg-26 from the decay of extinct Al-26. They seem to come from at least three sources, probably AGB stars, novae, and Wolf-Rayet stars.

Anders, Edward↗

NASA NTRS1994

Kupier prize lecture: Sources of solar-system carbon

We have tried to deconvolve Solar-System carbon into its sources, on the basis of C-12/C-13 ratios (equivalent to R). Interstellar SiC in meteorites, representing greater than 4.6-Ga-old stardust from carbon stars, is isotopically heavier (bar R = 38 +/- 2) than Solar-System carbon (89), implying that the latter contains an additional, light component. A likely source are massive stars, mainly Type II supernovae and Wolf-Rayet stars, which, being O-rich, eject their C largely as CO rather than carbonaceous dust. The fraction of such light C in the Solar System depends on R(sub light) in the source. For R(sub light) = 180-1025 (as in 'Group 4' meteoritic graphite spherules, which apparently came from massive stars greater than 4.6 Ga ago), the fraction of light C is 0.79-0.61. Similar results are obtained for present-day data on red giants and interstellar gas. Although both have become enriched in C-13 due to galactic evolution (to bar-R = 20 and 57), the fraction of the light component in interstellar gas again is near 0.7. (Here bar R represents the mean of a mixture calculated via atom fractions; it is not identical to the arithmetic mean R). Interstellar graphite, unlike SiC, shows a large peak at R approximately equal 90, near the solar value. Although some of the grains may be of local origin, others show anomalies in other elements and hence are exotic. Microdiamonds, with R = 93, also are exotic on the basis of their Xe and N. Apparently R approximately 90 was a fairly common composition 4.6 Ga ago, of stars as well as the ISM.

Anders, Edward↗

NASA NTRS1993

Interstellar Dust: Physical Processes

Dust is formed in stellar environments, and destroyed by sputtering, shattering and vaporization in shock waves due to cloud-cloud collisions and supernova blast waves. Dust is also destroyed during star formation. We review the dust formation and destruction balance. The calculated destruction time-scale is less than or equal to one billion years and the star dust injection time-scale is approx. 2.5 billion years. Hence, the fractions of elemental carbon and silicon locked up in stardust are less than 0.3 and less than 0.15, respectively. An efficient ISM dust formation route is therefore implied. In particular, in dense clouds dust grows; through the processes of coagulation and the accretion of gas phase molecules e.g. H20, CO, CH4. These icy materials may then be photoprocessed to refractory materials in more diffuse regions. The resulting carbonaceous grain mantle may actually be the glue that holds the coagulated grains together.

Jones, A. P.↗

NASA NTRS1998

Capture of Hypervelocity Particles with Low-Density Aerogel

Recent impact experiments conducted at Johnson Space Center supported a space-exposed flight instrument called the orbital debris collector (ODC) to see whether SiO2 acrogel performed adequately as a collector to capture cosmic dust particles and/or manmade debris, or whether additional development is needed. The first ODC was flown aboard the Mir for 18 months, while the second will be flown aboard a spacecraft (Stardust, to be launched in 1999) that will encounter the comet Wild 2 and return to Earth. Aerogels are highly porous materials that decelerate high-velocity particles without substantial melting or modifications to the particles' components; in other denser materials, these particles would melt or vaporize upon impact. The experimental data in this report must be considered somewhat qualitative because they are characterized by substantial, if not intolerable, scatter, possibly due to experimental difficulties in duplicating given sets of initial impact conditions. Therefore, this report is a chronological guide of the experimenters' attempts, difficulties, progress, and evaluations for future tests.

Hoerz, Friedrich↗