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  • 1
    Call number: H O 311
    Type of Medium: Monograph non-lending collection
    Pages: getrennte Zählung
    Location: Pendulum room
    Branch Library: GFZ Library
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  • 2
    Publication Date: 2018-06-05
    Description: The Long Duration Exposure Facility (LDEF) was host to several individual experiments designed to characterize aspects of the meteoroid and space-debris environment in low-Earth orbit. It was realized from the very start, however, that the most complete way to accomplish this goal was to exploit the meteoroid and debris record of the entire LDEF. The Meteoroid and Debris Special Investigation Group (M&D SIG) was organized to achieve this end. Two dominant goals of the M&D SIG are the documentation of the impact record of the entire LDEF, and the dissemination of this information to all interested workers. As a major step towards the accomplishment of these goals, we have prepared this publication describing the M&D SIG observations of impact features made during LDEF deintegration activities at KSC in the spring of 1990. It is hoped that this report will serve as a useful guide for spacecraft designers as well as for meteoroid and space-debris workers, and that it will spur further work on the LDEF impact-laden surfaces collected by the M&D SIG and now available for allocation to qualified investigators. An important aim is to present all data and descriptions of impact features in a form which, though terse, remains comprehensible to the wider community. There is a deliberate minimum of interpretations. Thus, this catalog is intended to serve as a guide to the impact features found on LDEF and is not intended to stand as a definitive interpretive work.
    Keywords: SPACECRAFT DESIGN, TESTING AND PERFORMANCE
    Type: NASA-TM-105463 , PUBL-84 , JSC-24608 , NAS 1.15:105463
    Format: application/pdf
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  • 3
    Publication Date: 2018-06-11
    Description: The Genesis spacecraft, launched in 2001, traveled to a Lagrangian point between the Earth and Sun to collect particles from the solar wind and return them to Earth. However, during the return of the spacecraft in 2004, the parachute failed to open during descent, and the Genesis spacecraft crashed into the Utah desert. Many of the solar wind collectors were broken into smaller pieces, and the field team rapidly collected the capsule and collector pieces for later assessment. On each of the next few days, the team discovered that various collectors had survived intact, including three of four concentrator targets. Within a month, the team had imaged more than 10,000 fragments and packed them for transport to the Astromaterials Acquisition and Curation Office within the ARES Directorate at JSC. Currently, the Genesis samples are curated along with the other extraterrestrial sample collections within ARES. Although they were broken and dirty, the Genesis solar wind collectors still offered the science community the opportunity to better understand our Sun and the solar system as a whole. One of the more highly prized concentrator collectors survived the crash almost completely intact. The Genesis Concentrator was designed to concentrate the solar wind by a factor of at least 20 so that solar oxygen and nitrogen isotopes could be measured. One of these materials was the Diamond-on-Silicon (DoS) concentrator target. Unfortunately, the DoS concentrator broke on impact. Nevertheless, the scientific value of the DoS concentrator target was high. The Genesis Allocation Committee received a request for approximately 1 cm(sup 2) of the DoS specimen taken near the focal point of the concentrator for the analysis of solar wind nitrogen isotopes. The largest fragment, Genesis sample 60000, was designated for this allocation and needed to be precisely cut. The requirement was to subdivide the designated sample in a manner that prevented contamination of the sample and minimized the risk of losing or breaking the precious requested sample fragment. The Genesis curator determined that the use of laser scribing techniques to "cut" a precise line and subsequently cleave the sample (in a controlled break of the sample along that line) was the best method for accomplishing the sample subdivision. However, there were risks, including excess heating of the sample, that could cause some of the implanted solar wind to be lost via thermal diffusion. Accidentally breaking the sample during the handling and cleaving process was an additional risk. Early in fiscal year 2013, to address this delicate, complicated task, the ARES Directorate assembled its top scientists to develop a cutting plan that would ensure success when applied to the actual concentrator target wafer; i.e., to produce an approximately 1 cm(sup 2) piece from the requested area of the wafer. The team, subsequently referred to as the JSC Genesis Tiger Team, spent months researching and testing parameters and techniques related to scribing, cleaving, transporting, handling, and holding (i.e., mounting) the specimen. The investigation required considerable "thinking outside the box," and many, many trials using nonflight wafer analogs. After all preliminary testing, the following method was adopted as the final cutting plan. It was used in two final end-to-end practice runs before being used on the actual flight target wafer. The wafer was oriented on the laser cutting stage with the 100 and 010 directions of the wafer parallel to the corresponding X and Y directions of the cutting stage. The laser was programed to scribe 31 lines of the appropriate length along the Y stage direction. The programed scribe lines were separated by 5 micron in the X direction. The laser parameters were set as follows: (1) The laser power was 0.5 watts; (2) each line consisted of 50 passes, with the Z position being advanced 5 micron per pass; and (3) 30 s would elapse before the next line was scribed to allow for wafer cool down from any possible heating via the laser. The ablated material that "stuck" in the "scribe-cut" was removed from the "cut" using an ultrasonic micro-tool. After all the ablated silicon was removed from the wafer, the wafer was repositioned in exactly the same orientation on the laser stage. The laser was focused using the bottom of the wafer channel, and the 31-line scribing pattern described above was reprogrammed using the Z position of the groove bottom as the starting Z value instead of the top wafer surface, which was used previously. Upon completion of the second set of scribes, the ultrasonic micro-tool was again used to clean out the cut. The wafer was remounted on the stage in exactly the same orientation as before. The laser was again focused on the bottom of the groove. This time, however, the laser was.programed to scribe only one line down the exact center of the channel. The final scribe line consisted of 100 passes with a Z advance of 5 micron per pass and with the laser power set at 0.5 watts. As mentioned above, the final cutting plan was practiced in two end-to-end trials using non-flight, triangular-shaped silicon wafers similar in size and orientation to the actual DOS 60000 target sample. The actual scribing of the triangular-shaped wafers required scribing two lines and cleaving (i.e. scribe-cleave, then scribe-cleave) to obtain the piece requested for allocation. Early in December 2012, after many months of experiments and practicing and perfecting the techniques and procedures, the team successfully subdivided the Genesis DoS 60000 target sample, one of the most scientifically important samples from the Genesis mission (figure 2). On December 17, 2012, the allocated piece of concentrator target sample was delivered to the requesting principal investigator.The cutting plan developed for the subdivision of this sample will be used as the model for subdividing future requested Genesis flight wafers (appropriately modified for different wafer types).
    Keywords: Lasers and Masers
    Type: ARES Biennial Report 2012 Final; 44-46; JSC-CN-30442
    Format: application/pdf
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  • 4
    Publication Date: 2018-06-11
    Description: We measured the chemical compositions of material from 23 particles in aerogel and residue in 7 craters in aluminum foil, collected during passage of the Stardust spacecraft through the coma of Comet 81P/Wild 2. These particles are chemically heterogeneous at the largest size-scale analyzed, ~180 nanograms. The mean chemical composition of this Wild 2 material agrees with the CI meteorite composition for the refractory elements Mg, Si, Cr, Fe, and Ni to 35%, and for Ca and Mn to 50%. The data suggest the moderately volatile elements Cu, Zn, and Ga may be enriched in this Wild 2 material.
    Keywords: Lunar and Planetary Science and Exploration
    Format: application/pdf
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  • 5
    Publication Date: 2019-01-25
    Description: Laboratory impact experiments are needed to understand the relationship between a measured penetration hole diameter and associated projectile dimension in the thermal blankets of experiment A0178, which occupied some 16 sq. m. These blankets are composed of 125 micron thick Teflon that has an Ag/enconel second mirror surface, backed by organic binder and Chemglaze paint for a total thickness of some 170 microns. While dedicated experiments are required to understand the penetration behavior of this compound target in detail, we report here on impact simulations sponsored by other projects into pure Teflon and aluminum targets. These experiments will allow first order interpretations of impact features on the Long Duration Exposure Facility (LDEF), and they will serve as guides for dedicated experiments that employ the real LDEF blankets, both exposed and unexposed, for a refined understanding of the LDEF's collisional environment. We employed a light gas gun to launch soda-lime glass spheres from 50 to 3200 microns in diameter that impacted targets of variable thickness. Penetration measurements are given.
    Keywords: SPACECRAFT DESIGN, TESTING AND PERFORMANCE
    Type: NASA. Langley Research Center, LDEF: 69 Months in Space. First Post-Retrieval Symposium, Part 1; p 581
    Format: text
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  • 6
    Publication Date: 2019-01-25
    Description: The comminution of planetary surfaces by exposure to continuous meteorite bombardment was simulated by impacting the same fragmental gabbro target 200 times. The role of comminution and in situ gardening of planetary regoliths was addressed. Mean grain size continuously decreased with increasing shot number. Initially it decreased linearly with accumulated energy, but at some stage comminution efficiency started to decrease gradually. Point counting techniques, aided by the electron microprobe for mineral identification, were performed on a number of comminution products. Bulk chemical analyses of specific grain size fractions were also carried out. The finest sizes ( 10 microns) display generally the strongest enrichment/depletion factors. Similar, if not exactly identical, trends are reported from lunar soils. It is, therefore, not necessarily correct to explain the chemical characteristics of various grain sizes via different admixtures of materials from distant source terrains. Differential comminution of local source rocks may be the dominating factor.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Lunar and Planetary Institute The 47th Ann. Meteoritical Soc. Meeting; 1 p
    Format: text
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  • 7
    Publication Date: 2018-06-11
    Description: The cometary tray of the NASA Stardust spacecraft s aerogel collector has been examined to study the dust that was captured during the 2004 fly by of comet 81P/Wild-2. An optical scan of the entire collector surface revealed 256 impact features in the aerogel (width 〉 100 microns). 20 aerogel blocks (out of a total of 132) were removed from the collector tray for a higher resolution optical scan and 186 tracks were observed (track length 〉 50 microns and width 〉 8 microns). The impact features were classified into three types based on their morphology. Laboratory calibrations were conducted which reproduce all three types. This work suggests that the cometary dust consisted of some cohesive, relatively strong particles as well as particles with a more friable or low cohesion matrix containing smaller strong grains. The calibrations also permitted a particle size distribution to be estimated for the cometary dust. We estimate that approximately 1200 particles bigger than 1 micron struck the aerogel. The cumulative size distribution of the captured particles was obtained and compared with observations made by active dust detectors during the encounter. At large sizes (〉20 microns) all measures of the dust are compatible, but at micrometer scales and smaller discrepancies exist between the various measurement systems which may reflect structure in the dust flux (streams, clusters etc.) along with some possible instrument effects.
    Keywords: Astronomy
    Format: application/pdf
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  • 8
    Publication Date: 2018-06-11
    Description: High-resolution images from the Mars Orbiter Camera reveal impact craters as small as 10 m [1], and still smaller craters (〈 0.5 m) have been inferred from surface boulders at the Pathfinder landing site [2]. Any small-scale impact environment at scales of meters or smaller would obviously be a potent contributor to erosive processes on Mars, to the small-scale evolution of its surface, and to mineralogic/ compositional alterations of its surface materials. It is not very clear from the analysis of Viking and Pathfinder images, however, what the smallest craters are on Mars. As a consequence, it might be informative to consult atmospheric-entry calculations that specify the smallest meteoroid able to survive passage through the present martian atmosphere. We conducted such calculations and perceive them as providing useful constraints for understanding small-scale surface processes on Mars and as possible guides for the interpretation of surface images from past and future lander missions.
    Keywords: Lunar and Planetary Science and Exploration
    Type: Lunar and Planetary Science XXXV: Mars Impact Cratering; LPI-Contrib-1197
    Format: text
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  • 9
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 106 (1921), S. 663-663 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] ABOUT thirty-five years ago Sir Norman Lockyer held that certain of the reddish stars are probably in an early stage of development. It was given out yesterday in Press dispatches from Chicago that Prof. Michelson had announced to the American Physical Society and the American Association for ...
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 81 (1909), S. 275-275 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] IN your issue of July 29 your reviewer devotes some space to my paper on the origin of the planetary system (Astronomische Nachrichten, No. 4308), and closes by asking, “Why, for instance, on the hypothesis of capture, are the vast majority of the orbits near the plane of the ecliptic and their ...
    Type of Medium: Electronic Resource
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