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At least 127 records · Page 7

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NASA NTRS1978

Feature discrimination/identification based upon SAR return variations

A study of the statistics of The look-to-look variation statistics in the returns recorded in-flight by a digital, realtime SAR system are analyzed. The determination that the variations in the look-to-look returns from different classes do carry information content unique to the classes was illustrated by a model based on four variants derived from four look in-flight SAR data under study. The model was limited to four classes of returns: mowed grass on a athletic field, rough unmowed grass and weeds on a large vacant field, young fruit trees in a large orchard, and metal mobile homes and storage buildings in a large mobile home park. The data population in excess of 1000 returns represented over 250 individual pixels from the four classes. The multivariant discriminant model operated on the set of returns for each pixel and assigned that pixel to one of the four classes, based on the target variants and the probability distribution function of the four variants for each class.

Rasco, W. A., Sr.↗

NASA NTRS1982

The optical and radiation field signatures produced by lightning return strokes

Typical examples of the signals that are produced by first and subsequent return strokes in cloud-to-ground lightning on a microsecond time scale are presented. Statistics on the structure of the waveforms and the radiance of the channels are given. The relationship between the light signals and the associated electric field signatures is discussed. It is shown that the initial light signal from a return stroke tends to be linear for about 15 microsec and then rises more slowly to a peak that is delayed by approximately 60 microsec from the electric field peak. It is thought that the transition between the fast linear portion and the slower rise may be due to the return stroke entering the cloud base. A small percentage of the records suggest that two different branches of the same stepped leader can initiate separate return strokes. The light pulses from cloud discharges tend to be smaller and to vary more slowly than those from return strokes.

Guo, C.↗

NASA NTRS1985

Return currents in solar flares - Collisionless effects

If the primary, precipitating electrons in a solar flare are unstable to beam plasma interactions, it is shown that strong Langmuir turbulence can seriously modify the way in which a return current is carried by the background plasma. In particular, the return (or reverse) current will not be carried by the bulk of the electrons, but by a small number of high velocity electrons. For beam/plasma densities greater than 0.01, this can reduce the effects of collisions on the return current. For higher density beams where the return current could be unstable to current driven instabilities, the effects of strong turbulence anomalous resistivity is shown to prevent the appearance of such instabilities. Again in this regime, how the return current is carried is determined by the beam generated strong turbulence.

Rowland, H. L.↗

NASA NTRS1985

Scientific objectives for a 1996 Mars Sample Return Mission

The Mars Sample Return Mission, designed to return a variety of surface and subsurface samples as well as atmospheric samples, is described. Primary information about the planet is essential to understanding its place in the evolution of the solar system. The most accurate landing techniques will be used to place the lander near geologically interesting features. A capable rover will be an essential element of the sample collection strategy to maximize the diversity of the samples. The sample collection and return systems will keep the samples at Mars ambient conditions or colder to preserve the abundances and distribution of volatile components. Planetary quarantine is an important consideration for both the Mars lander and the earth return vehicle. Quarantine procedures must be consistent with the primary objectives of the mission and must not compromise the investigations of the returned samples.

Blanchard, D. P.↗

NASA NTRS1993

Two-dimensional velocity, optical risetime, and peak current estimates for natural positive lightning return strokes

Velocities, optical risetimes, and transmission line model peak currents for seven natural positive return strokes are reported. The average 2D positive return stroke velocity for channel segments of less than 500 m in length starting near the base of the channel is 0.8 +/- 0.3 x 10 exp 8 m/s, which is slower than the present corresponding average velocity for natural negative first return strokes of 1.7 +/- 0.7 x 10 exp 8/s. It is inferred that positive stroke peak currents in the literature, which assume the same velocity as negative strokes, are low by a factor of 2. The average 2D positive return stroke velocity for channel segments of greater than 500 m starting near the base of the channel is 0.9 +/- 0.4 x 10 exp 8 m/s. The corresponding average velocity for the present natural negative first strokes is 1.2 +/- 0.6 x 10 exp 8 m/s. No significant velocity change with height is found for positive return strokes.

Mach, Douglas M.↗

NASA NTRS1993

Project Hyreus: Mars sample return mission utilizing in situ propellant production

Project Hyreus is an unmanned Mars sample return mission that utilizes propellants manufactured in situ from the Martian atmosphere for the return voyage. A key goal of the mission is to demonstrate the considerable benefits of using indigenous resources and to test the viability of this approach as a precursor to manned Mars missions. The techniques, materials, and equipment used in Project Hyreus represent those that are currently available or that could be developed and readied in time for the proposed launch date in 2003. Project Hyreus includes such features as a Mars-orbiting satellite equipped with ground-penetrating radar, a large rover capable of sample gathering and detailed surface investigations, and a planetary science array to perform on-site research before samples are returned to Earth. Project Hyreus calls for the Mars Landing Vehicle to land in the Mangala Valles region of Mars, where it will remain for approximately 1.5 years. Methane and oxygen propellant for the Earth return voyage will be produced using carbon dioxide from the Martian atmosphere and a small supply of hydrogen brought from Earth. This process is key to returning a large Martian sample to Earth with a single Earth launch.

Abrego, Anita↗

NASA NTRS2000

NEA Multi-Chamber Sample Return Container with Hermetic Sealing

A sample return container is being developed by Honeybee Robotics to receive samples from a derivative of the Champollion/ST4 Sample Acquisition and Transfer Mechanism or other samplers such as the 'Touch and Go' Surface Sampler (TGSS), and then hermetically seal the samples for a sample return mission. The container is enclosed in a phase change material (PCM) chamber to prevent phase change during return and re-entry to earth. This container is designed to operate passively with no motors and actuators. Using the rotation axis of the TGSS sampler for interfacing, transferring and sealing samples, the container consumes no electrical power and therefore minimizes sample temperature change. The circular container houses multiple isolated canisters, which will be sealed individually for samples acquired from different sites or depths. The TGSS based sampler indexes each canister to the sample transfer position, below the index interface for sample transfer. After sample transfer is completed, the sampler indexes a seal carrier, which lines up seals with the openings of the canisters. The sampler moves to the sealing interface and seals the sample canisters one by one. The sealing interface can be designed to work with C-seals, knife edge seals and cup seals. This sample return container is being developed by Honeybee Robotics in collaboration with the JPL Exploration Technology program. A breadboard system of the sample return container has been recently completed and tested. Additional information is contained in the original extended abstract.

Rafeek, Shaheed↗

NASA NTRS2002

A Draft Protocol for Detecting Possible Biohazards in Martian Samples Returned to Earth

In preparation for missions to Mars that will involve the return of samples, it is necessary to prepare for the safe receiving, handling, testing, distributing, and archiving of martian materials here on Earth. Previous groups and committees have studied selected aspects of sample return activities, but a specific protocol for handling and testing of returned -=1 samples from Mars remained to be developed. To refine the requirements for Mars sample hazard testing and to develop criteria for the subsequent release of sample materials from precautionary containment, NASA Planetary Protection Officer, working in collaboration with CNES, convened a series of workshops to produce a Protocol by which returned martian sample materials could be assessed for biological hazards and examined for evidence of life (extant or extinct), while safeguarding the samples from possible terrestrial contamination. The Draft Protocol was then reviewed by an Oversight and Review Committee formed specifically for that purpose and composed of senior scientists. In order to preserve the scientific value of returned martian samples under safe conditions, while avoiding false indications of life within the samples, the Sample Receiving Facility (SRF) is required to allow handling and processing of the Mars samples to prevent their terrestrial contamination while maintaining strict biological containment. It is anticipated that samples will be able to be shipped among appropriate containment facilities wherever necessary, under procedures developed in cooperation with international appropriate institutions. The SRF will need to provide different types of laboratory environments for carrying out, beyond sample description and curation, the various aspects of the protocol: Physical/Chemical analysis, Life Detection testing, and Biohazard testing. The main principle of these tests will be described and the criteria for release will be discussed, as well as the requirements for the SRF and its personnel.

Viso, M.↗

NASA NTRS1993

Project Hyreus: Mars Sample Return Mission Utilizing in Situ Propellant Production

Bruckner, A. P.↗

NASA NTRS2007

Lunar Return Reentry Thermal Analysis of a Generic Crew Exploration Vehicle Wall Structures

Thermostructural analysis was performed on generic crew exploration vehicle (GCEV) heat shielded wall structures subjected to reentry heating rates based on five potential lunar return reentry trajectories. The GCEV windward outer wall is fabricated with a graphite/epoxy composite honeycomb sandwich panel and the inner wall with an aluminum honeycomb sandwich panel. The outer wall is protected with an ablative Avcoat-5026-39H/CG thermal protection system (TPS). A virtual ablation method (a graphical approximation) developed earlier was further extended, and was used to estimate the ablation periods, ablation heat loads, and the TPS recession layer depths. It was found that up to 83 95 percent of the total reentry heat load was dissipated in the TPS ablation process, leaving a small amount (3-15 percent) of the remaining total reentry heat load to heat the virgin TPS and maintain the TPS surface at the ablation temperature, 1,200 F. The GCEV stagnation point TPS recession layer depths were estimated to be in the range of 0.280-0.910 in, and the allowable minimum stagnation point TPS thicknesses that could maintain the substructural composite sandwich wall at the limit temperature of 300 F were found to be in the range of 0.767-1.538 in. Based on results from the present analyses, the lunar return abort ballistic reentry was found to be quite attractive because it required less TPS weight than the lunar return direct, the lunar return skipping, or the low Earth orbit guided reentry, and only 11.6 percent more TPS weight than the low Earth orbit ballistic reentry that will encounter a considerable weight penalty to obtain the Earth orbit. The analysis also showed that the TPS weight required for the lunar return skipping reentry was much more than the TPS weight necessary for any of the other reentry trajectories considered.

Ko, William L.↗

NASA NTRS2009

COMPASS Final Report: Near Earth Asteroids Rendezvous and Sample Earth Returns (NEARER)

In this study, the Collaborative Modeling for Parametric Assessment of Space Systems (COMPASS) team completed a design for a multi-asteroid (Nereus and 1996 FG3) sample return capable spacecraft for the NASA In-Space Propulsion Office. The objective of the study was to support technology development and assess the relative benefits of different electric propulsion systems on asteroid sample return design. The design uses a single, heritage Orion solar array (SA) (approx.6.5 kW at 1 AU) to power a single NASA Evolutionary Xenon Thruster ((NEXT) a spare NEXT is carried) to propel a lander to two near Earth asteroids. After landing and gathering science samples, the Solar Electric Propulsion (SEP) vehicle spirals back to Earth where it drops off the first sample s return capsule and performs an Earth flyby to assist the craft in rendezvousing with a second asteroid, which is then sampled. The second sample is returned in a similar fashion. The vehicle, dubbed Near Earth Asteroids Rendezvous and Sample Earth Returns (NEARER), easily fits in an Atlas 401 launcher and its cost estimates put the mission in the New Frontier s (NF's) class mission.

Oleson, Steven R.↗

NASA NTRS2010

Orion Optical Navigation for Loss of Communication Lunar Return Contingencies

The Orion Crew Exploration Vehicle (CEV) will replace the Space Shuttle and serve as the next-generation spaceship to carry humans back to the Moon for the first time since the Apollo program. For nominal lunar mission operations, the Mission Control Navigation team will utilize radiometric measurements to determine the position and velocity of Orion and uplink state information to support Lunar return. However, in the loss of communications contingency return scenario, Orion must safely return the crew to the Earth's surface. The navigation design solution for this loss of communications scenario is optical navigation consisting of lunar landmark tracking in low lunar orbit and star- horizon angular measurements coupled with apparent planetary diameter for Earth return trajectories. This paper describes the optical measurement errors and the navigation filter that will process those measurements to support navigation for safe crew return.

Getchius, Joel↗

NASA NTRS2011

Almahata Sitta and Brecciated Ureilites: Insights into the Heterogeneity of Asteroids and Implications for Sample Return

Analysis of samples returned to terrestrial laboratories enables more precise measurements and a wider range of techniques to be utilized than can be achieved with either remote sensing or rover instruments. Furthermore, returning samples to Earth allows them to be stored and re-examined with future technology. Following the success of the Hayabusa mission, returning samples from asteroids should be a high priority for understanding of early solar system evolution, planetary formation and differentiation. Meteorite falls provide us with materials and insight into asteroidal compositions. Almahata Sitta (AS) was the first meteorite fall from a tracked asteroid (2008 TC3) [1] providing a rare opportunity to compare direct geochemical observations with remote sensing data. Although AS is predominantly ureilitic, multiple chondritic fragments have been associated with this fall [2,3]. This is not unique, with chondritic fragments being found in many howardite samples (as described in a companion abstract [4]) and in brecciated ureilites, some of which are known to represent ureilitic regolith [5-7]. The heterogeneity of ureilite samples, which are thought to all originate from a single asteroidal ureilite parent body (UPB) [5], gives us information about both internal and external asteroidal variations. This has implications both for the planning of potential sample return missions and the interpretation of material returned to Earth. This abstract focuses on multiple fragments of two meteorites: Almahata Sitta (AS); and Dar al Gani (DaG) 1047 (a highly brecciated ureilite, likely representative of ureilite asteroidal regolith).

Ross, A. J.↗

NASA NTRS2011

MEPAG Recommendations for a 2018 Mars Sample Return Caching Lander - Sample Types, Number, and Sizes

The return to Earth of geological and atmospheric samples from the surface of Mars is among the highest priority objectives of planetary science. The MEPAG Mars Sample Return (MSR) End-to-End International Science Analysis Group (MEPAG E2E-iSAG) was chartered to propose scientific objectives and priorities for returned sample science, and to map out the implications of these priorities, including for the proposed joint ESA-NASA 2018 mission that would be tasked with the crucial job of collecting and caching the samples. The E2E-iSAG identified four overarching scientific aims that relate to understanding: (A) the potential for life and its pre-biotic context, (B) the geologic processes that have affected the martian surface, (C) planetary evolution of Mars and its atmosphere, (D) potential for future human exploration. The types of samples deemed most likely to achieve the science objectives are, in priority order: (1A). Subaqueous or hydrothermal sediments (1B). Hydrothermally altered rocks or low temperature fluid-altered rocks (equal priority) (2). Unaltered igneous rocks (3). Regolith, including airfall dust (4). Present-day atmosphere and samples of sedimentary-igneous rocks containing ancient trapped atmosphere Collection of geologically well-characterized sample suites would add considerable value to interpretations of all collected rocks. To achieve this, the total number of rock samples should be about 30-40. In order to evaluate the size of individual samples required to meet the science objectives, the E2E-iSAG reviewed the analytical methods that would likely be applied to the returned samples by preliminary examination teams, for planetary protection (i.e., life detection, biohazard assessment) and, after distribution, by individual investigators. It was concluded that sample size should be sufficient to perform all high-priority analyses in triplicate. In keeping with long-established curatorial practice of extraterrestrial material, at least 40% by mass of each sample should be preserved to support future scientific investigations. Samples of 15-16 grams are considered optimal. The total mass of returned rocks, soils, blanks and standards should be approximately 500 grams. Atmospheric gas samples should be the equivalent of 50 cubic cm at 20 times Mars ambient atmospheric pressure.

Allen, Carlton C.↗

NASA NTRS2012

Multiple Smaller Missions as a Direct Pathway to Mars Sample Return

Recent discoveries by the Mars Exploration Rovers, Mars Express, Mars Odyssey, and Mars Reconnaissance Orbiter spacecraft include multiple, tantalizing astrobiological targets representing both past and present environments on Mars. The most desirable path to Mars Sample Return (MSR) would be to collect and return samples from that site which provides the clearest examples of the variety of rock types considered a high priority for sample return (pristine igneous, sedimentary, and hydrothermal). Here we propose an MSR architecture in which the next steps (potentially launched in 2018) would entail a series of smaller missions, including caching, to multiple landing sites to verify the presence of high priority sample return targets through in situ analyses. This alternative architecture to one flagship-class sample caching mission to a single site would preserve a direct path to MSR as stipulated by the Planetary Decadal Survey, while permitting investigation of diverse deposit types and providing comparison of the site of returned samples to other aqueous environments on early Mars

Niles, P. B.↗

NASA NTRS2013

A Mars Sample Return Sample Handling System

We present a sample handling system, a subsystem of the proposed Dragon landed Mars Sample Return (MSR) mission [1], that can return to Earth orbit a significant mass of frozen Mars samples potentially consisting of: rock cores, subsurface drilled rock and ice cuttings, pebble sized rocks, and soil scoops. The sample collection, storage, retrieval and packaging assumptions and concepts in this study are applicable for the NASA's MPPG MSR mission architecture options [2]. Our study assumes a predecessor rover mission collects samples for return to Earth to address questions on: past life, climate change, water history, age dating, understanding Mars interior evolution [3], and, human safety and in-situ resource utilization. Hence the rover will have "integrated priorities for rock sampling" [3] that cover collection of subaqueous or hydrothermal sediments, low-temperature fluidaltered rocks, unaltered igneous rocks, regolith and atmosphere samples. Samples could include: drilled rock cores, alluvial and fluvial deposits, subsurface ice and soils, clays, sulfates, salts including perchlorates, aeolian deposits, and concretions. Thus samples will have a broad range of bulk densities, and require for Earth based analysis where practical: in-situ characterization, management of degradation such as perchlorate deliquescence and volatile release, and contamination management. We propose to adopt a sample container with a set of cups each with a sample from a specific location. We considered two sample cups sizes: (1) a small cup sized for samples matching those submitted to in-situ characterization instruments, and, (2) a larger cup for 100 mm rock cores [4] and pebble sized rocks, thus providing diverse samples and optimizing the MSR sample mass payload fraction for a given payload volume. We minimize sample degradation by keeping them frozen in the MSR payload sample canister using Peltier chip cooling. The cups are sealed by interference fitted heat activated memory alloy caps [5] if the heating does not affect the sample, or by crimping caps similar to bottle capping. We prefer cap sealing surfaces be external to the cup rim to prevent sample dust inside the cups interfering with sealing, or, contamination of the sample by Teflon seal elements (if adopted). Finally the sample collection rover, or a Fetch rover, selects cups with best choice samples and loads them into a sample tray, before delivering it to the Earth Return Vehicle (ERV) in the MSR Dragon capsule as described in [1] (Fig 1). This ensures best use of the MSR payload mass allowance. A 3 meter long jointed robot arm is extended from the Dragon capsule's crew hatch, retrieves the sample tray and inserts it into the sample canister payload located on the ERV stage. The robot arm has capacity to obtain grab samples in the event of a rover failure. The sample canister has a robot arm capture casting to enable capture by crewed or robot spacecraft when it returns to Earth orbit

Wilson, David↗

NASA NTRS2011

Airborne Observation of the Hayabusa Sample Return Capsule Re-Entry

NASA Ames Research Center and the SETI Institute collaborated on an effort to observe the Earth re-entry of the Japan Aerospace Exploration Agency's Hayabusa sample return capsule. Hayabusa was an asteroid exploration mission that retrieved a sample from the near-Earth asteroid Itokawa. Its sample return capsule re-entered over the Woomera Prohibited Area in southern Australia on June 13, 2010. Being only the third sample return mission following NASA's Genesis and Stardust missions, Hayabusa's return was a rare opportunity to collect aerothermal data from an atmospheric entry capsule returning at superorbital speeds. NASA deployed its DC-8 airborne laboratory and a team of international researchers to Australia for the re-entry. For approximately 70 seconds, spectroscopic and radiometric imaging instruments acquired images and spectra of the capsule, its wake, and destructive re-entry of the spacecraft bus. Once calibrated, spectra of the capsule will be interpreted to yield data for comparison with and validation of high fidelity and engineering simulation tools used for design and development of future atmospheric entry system technologies. A brief summary of the Hayabusa mission, the preflight preparations and observation mission planning, mission execution, and preliminary spectral data are documented.

Spectroscopy↗

NASA NTRS2018

The CAESAR New Frontiers Comet Sample Return Mission

The Comet Astrobiology Exploration Sample Return (CAESAR) mission is one of two finalists selected by NASA for Phase A study in the New Frontiers program. CAESAR will acquire a minimum of 80 grams of material from the surface of comet 67P/Churuyumov-Gerasimenko and return it to Earth for laboratory analysis. CAESAR preserves much of the science of a cryogenic sample return by retaining volatiles in a dedicated reservoir securely separated from the solid sample. Comet 67P was selected based on its favorable orbital geometry and the risk reduction and scientific context provided by the ESA (European Space Agency)'s Rosetta mission. CAESAR's objectives are to understand the origins of the Solar System starting materials and how these components came together to form planets and give rise to life. We also seek to resolve the conflicting views of comet origins arising from the Stardust and Rosetta missions. While the greater than 1 micron solids returned by Stardust originated in the hot, inner solar nebula, measurements by Rosetta suggest 67P volatiles formed at cryogenic temperatures and remained unchanged for billions of years. This dichotomy provides the rationale for returning both solid and gaseous samples.

CAESAR New Frontiers↗