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At least 163 records · Page 9
All sourcesNASA NTRSDOE OSTI
NASA NTRS2012

Evaluating Core Quality for a Mars Sample Return Mission

Sample return missions, including the proposed Mars Sample Return (MSR) mission, propose to collect core samples from scientifically valuable sites on Mars. These core samples would undergo extreme forces during the drilling process, and during the reentry process if the EEV (Earth Entry Vehicle) performed a hard landing on Earth. Because of the foreseen damage to the stratigraphy of the cores, it is important to evaluate each core for rock quality. However, because no core sample return mission has yet been conducted to another planetary body, it remains unclear as to how to assess the cores for rock quality. In this report, we describe the development of a metric designed to quantitatively assess the mechanical quality of any rock cores returned from Mars (or other planetary bodies). We report on the process by which we tested the metric on core samples of Mars analogue materials, and the effectiveness of the core assessment metric (CAM) in assessing rock core quality before and after the cores were subjected to shocking (g forces representative of an EEV landing).

Mars samples↗
DOE OSTI2019

Current Status of the Russian Research Reactor Fuel Return Program

In 1999, the U.S. Department of Energy (DOE), together with the International Atomic Energy Agency (IAEA) and the Russian Federation, agreed to start a new nuclear non-proliferation initiative to return Russian/Soviet-origin highly enriched uranium (HEU) back to its country of origin. Trilateral discussions among the U.S., the Russian Federation, and the IAEA identified more than 20 research reactors in 16 countries (Belarus, Bulgaria, China, Czech Republic, DPRK, Germany, Hungary, Kazakhstan, Latvia, Libya, Poland, Romania, Serbia, Ukraine, Uzbekistan, and Vietnam) that had Russian/Soviet-origin HEU. In 2000, the IAEA Director General sent a letter to 16 countries asking for their willingness to return this spent HEU fuel to the Russian Federation. Fourteen countries responded positively to the Director General’s letter. The primary goal of the Russian Research Reactor Fuel Return (RRRFR) program, managed by DOE’s National Nuclear Security Administration, Office of Material Management and Minimization, is to advance nuclear nonproliferation objectives by encouraging eligible countries to convert their research reactors from HEU to low-enriched uranium (LEU) fuel and to eliminate stockpiles of HEU. In May 2004, the United States and the Russian Federation signed a Government-to-Government Agreement that established the legal framework necessary for cooperation between the United States and the Russian Federation for the return of research/test reactor fuel from eligible countries. To date, the RRRFR program has completed sixty-three successful operations to repatriate almost 2,300 kg of Russian-origin HEU fresh and spent fuel. All Russian-origin HEU has been completely removed from 12 countries: Bulgaria, the Czech Republic, Hungary, Georgia, Latvia, Libya, Poland, Romania, Serbia, Ukraine, Uzbekistan, and Vietnam. At the present time Russian-origin HEU remains in Kazakhstan, Belarus, Germany, DPRK, and China. This paper describes the current status of the RRRFR program and preparations for upcoming HEU removal and down-blending activities.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2026

CHESS 2025: Discrete-return LiDAR point clouds from NEON AOP surveys

This dataset provides Level 1 (L1) discrete-return light detection and ranging (LiDAR) point cloud data collected for the 2025 Colorado Headwaters Ecological Spectroscopy Study (CHESS). These data were acquired to enable characterization of vegetation structure and other three-dimensional features of the land surface, and to evaluate structural changes that may have occurred between a prior LiDAR acquisition in 2018 and the 2025 overflight. The data were acquired over three study domains in the Upper Gunnison river basin: the upper East River watershed (CRBU); Almont Triangle and Taylor Canyon (ALMO); and Upper Taylor River watershed (UPTA) between 2025-06-13 and 2025-07-15. LiDAR data were acquired using the Optech Galaxy Prime Airborne LiDAR Terrain Mapper onboard the National Ecological Observatory Network (NEON) Airborne Observation Platform (AOP). These are the primary unclassified discrete-return LiDAR data delivered by NEON and are provided per flightline as LASzip (LAZ) 1.4 Format 6 files. Data were processed following the workflow described in the NEON L0-to-L1 Discrete Return LiDAR Algorithm Theoretical Basis Document (Krause and Goulden 2022). Each record in the unclassified point clouds represents a geolocated laser target/return recorded by the LiDAR system, with values for X, Y, Z position and return intensity. All point coordinates are provided in meters. Horizontal coordinates are referenced in Universal Transverse Mercator (UTM) zone 13N and the World Geodetic System (WGS) 1984 ensemble datum. Elevations are referenced to Geoid12A. Flight metadata describing flightline boundaries and positional uncertainty by point are also included. CHESS Project Description: The Colorado Headwaters Ecological Spectroscopy Study (CHESS) comprised a multi-week airborne remote sensing and field observation campaign in the Upper Gunnison Basin, Colorado, conducted in June and July of 2025. Airborne remote sensing was conducted by the National Ecological Observatory Network Airborne Observation Platform (NEON AOP), concurrent with a field campaign run by the Rocky Mountain Biological Laboratory (RMBL), the Lawrence Berkeley National Laboratory (LBNL) and SLAC National Accelerator Laboratory Watershed Function Science Focus Area (SFA), and NASA-JPL (Jet Propulsion Laboratory) Earth Surface Mineral Dust Source Investigation (EMIT) program. Between June 10 and July 18, 2025, the NEON AOP flight team collected high-resolution aerial imaging spectroscopy and Light Detection and Ranging (LiDAR) data over three domains: the Upper East River (CRBU), Almont Triangle (ALMO), and the Upper Taylor Basin (UPTA). In coordination with the flights, a field campaign acquired ground-truth observations, including observations of vegetation composition, foliar traits, forest demography, and subsurface properties in 18 core sampling areas within the domains. Additional surface water observations were taken at over 380 point locations. All CHESS campaign datasets can be found within the CHESS ESS-DIVE data portal: https://data.ess-dive.lbl.gov/portals/chess. Funding Acknowledgement: Field and remote-sensing data acquisition was performed under a grant from the National Aeronautics and Space Administration (80NSSC24K1005). This work was also supported by the Watershed Function Science Focus Area at Lawrence Berkeley National Laboratory funded by the US Department of Energy, Office of Science, Biological and Environmental Research under Contract No. DE-AC02-05CH11231.

2018 NEON and 2025 CHESS Campaigns↗
NASA NTRS1963

Lunar Flight Study Series: Volume 5. Trajectories in the Earth-Moon Space with Symmetrical Free Return Properties

An extensive investigation has been made of the characteristics of so-called "free return" trajectories. For the purposes of the study., these trajectories are defined as having certain symmetric properties which afford flight to the vicinity of the moon and return to earth without need for propulsion after the initial boost phase. The restricted three-body model for the earth-moon-probe system is used throughout. Two kinds of free return trajectories are shown to -exist and are studied. Of particular interest is the fact that for one kind of free return path, the largest inclination which can be achieved between the flight plane at periselenum and the plane of the moon's orbit about earth is about 10. 8 degrees while for the other kind of path the largest possible inclination is dependent on ·the radius at periselenum. In this case the inclination is limited to about 14 degrees or less for periselenum radius of 1938 km, but may be as great as 90 degrees with periselenum radius of 21150 km. Trajectories are also demonstrated which pass in front of the moon. These exhibit inclination behavior very much like that given by trajectories which go behind the moon. The injection velocity for these trajectories also changes only slightly from the circumlunar trajectories (less than 2 m/s for periselenum radius of 1938 km). However, the position of injection is changed considerably and the flight time may be increased by as much as five times that for circumlunar flight.

RETURN-TO-EARTH PHASE↗
NASA NTRS2014

Mars Sample Return Using Commercial Capabilities: Mission Architecture Overview

Mars Sample Return (MSR) is the highest priority science mission for the next decade as recommended by the recent Decadal Survey of Planetary Science. This paper presents an overview of a feasibility study for an MSR mission. The objective of the study was to determine whether emerging commercial capabilities can be used to reduce the number of mission systems and launches required to return the samples, with the goal of reducing mission cost. We report the feasibility of a complete and closed MSR mission design using the following scenario that covers three synodic launch opportunities, beginning with the 2022 opportunity: A Falcon Heavy injects a SpaceX Red Dragon capsule and trunk onto a Trans Mars Injection (TMI) trajectory. The capsule is modified to carry all the hardware needed to return samples collected on Mars including a Mars Ascent Vehicle (MAV), an Earth Return Vehicle (ERV), and hardware to transfer a sample collected in a previously landed rover mission to the ERV. The Red Dragon descends to land on the surface of Mars using Super Sonic Retro Propulsion (SSRP). After previously collected samples are transferred to the ERV, the single-stage MAV launches the ERV from the surface of Mars. The MAV uses a storable liquid bi-propellant propulsion system to deliver the ERV to a Mars phasing orbit. After a brief phasing period, the ERV, which also uses a storable bi-propellant system, performs a Trans Earth Injection (TEI) burn. Upon arrival at Earth, the ERV performs Earth and lunar swing-bys and is placed into a lunar trailing circular orbit - an Earth orbit, at lunar distance. A later mission, using Dragon and launched by a Falcon Heavy, performs a rendezvous with the ERV in the lunar trailing orbit, retrieves the sample container and breaks the chain of contact with Mars by transferring the sample into a sterile and secure container. With the sample contained, the retrieving spacecraft makes a controlled Earth re-entry preventing any unintended release of pristine martian materials into the Earth's biosphere. The analysis methods employed standard and specialized aerospace engineering tools. Mission system elements were analyzed with either direct techniques or by using parametric mass estimating relationships (MERs). The architecture was iterated until overall mission convergence was achieved on at least one path. Subsystems analyzed in this study include support structures, power system, nose fairing, thermal insulation, actuation devices, MAV exhaust venting, and GN&C. Best practice application of loads, mass growth contingencies, and resource margins were used. For Falcon Heavy capabilities and Dragon subsystems we utilized publically available data from SpaceX, published analyses from other sources, as well as our own engineering and aerodynamic estimates. Earth Launch mass is under 11 mt, which is within the estimated capability of a Falcon Heavy, with margin. Total entry masses between 7 and 10 mt were considered with closure occurring between 9 and 10 mt. Propellant mass fractions for each major phase of the EDL - Entry, Terminal Descent, and Hazard Avoidance - have been derived. An assessment of the effect of the entry conditions on the thermal protection system (TPS), currently in use for Dragon missions, shows no significant stressors. A useful payload mass of 2.0 mt is provided and includes mass growth allowances for the MAV, the ERV, and mission unique equipment. We also report options for the MAV and ERV, including propulsion systems, crewed versus robotic retrieval mission, as well as direct Earth entry. International planetary protection policies as well as verifiable means of compliance will have a large impact on any MSR mission design. We identify areas within our architecture where such impacts occur. We also describe preliminary compliance measures that will be the subject of future work. This work shows that emerging commercial capabilities as well as new methodologies can be used to efficiently support an important planetary science objective. The work also has applications for human exploration missions that use propulsive EDL techniques

Red Dragon↗
NASA NTRS2013

Mars Sample Return Using Commercial Capabilities: Mission Architecture Overview

Mars Sample Return (MSR) is the highest priority science mission for the next decade as recommended by the recent Decadal Survey of Planetary Science. This paper presents an overview of a feasibility study for a MSR mission. The objective of the study was to determine whether emerging commercial capabilities can be used to reduce the number of mission systems and launches required to return the samples, with the goal of reducing mission cost. The major element required for the MSR mission are described and include an integration of the emerging commercial capabilities with small spacecraft design techniques; new utilizations of traditional aerospace technologies; and recent technological developments. We report the feasibility of a complete and closed MSR mission design using the following scenario that covers three synodic launch opportunities, beginning with the 2022 opportunity: A Falcon Heavy injects a SpaceX Red Dragon capsule and trunk onto a Trans Mars Injection (TMI) trajectory. The capsule is modified to carry all the hardware needed to return samples collected on Mars including a Mars Ascent Vehicle (MAV); an Earth Return Vehicle (ERV); and hardware to transfer a sample collected in a previously landed rover mission to the ERV. The Red Dragon descends to land on the surface of Mars using Supersonic Retro Propulsion (SRP). After previously collected samples are transferred to the ERV, the single-stage MAV launches the ERV from the surface of Mars to a Mars phasing orbit. The MAV uses a storable liquid, pump fed bi-propellant propulsion system. After a brief phasing period, the ERV, which also uses a storable bi-propellant system, performs a Trans Earth Injection (TEI) burn. Once near Earth the ERV performs Earth and lunar swing-bys and is placed into a Lunar Trailing Orbit (LTO0 - an Earth orbit, at lunar distance. A later mission, using a Dragon and launched by a Falcon Heavy, performs a rendezvous with the ERV in the lunar trailing orbit, retrieves the sample container and breaks the chain of contact with Mars by transferring the sample into a sterile and secure container. With the sample contained, the retrieving spacecraft, makes a controlled Earth re-entry preventing any unintended release of pristine Martian materials into the Earth's biosphere. Other capsule type vehicles and associated launchers may be applicable. The analysis methods employed standard and specialized aerospace engineering tools. Mission system elements were analyzed with either direct techniques or by using parametric mass estimating relationships (MERs). The architecture was iterated until overall mission convergence was achieved on at least one path. Subsystems analyzed in this study include support structures, power system, nose fairing, thermal insulation, actuation devices, MAV exhaust venting, and GN&C. Best practice application of loads, mass growth contingencies, and resource margins were used. For Falcon Heavy capabilities and Dragon subsystems we utilized publically available data from SpaceX; published analyses from other sources; as well as our own engineering and aerodynamic estimates. Earth Launch mass is under 11 mt, which is within the estimated capability of a Falcon Heavy, with margin. Total entry masses between 7 and 10 mt were considered with closure occurring between 9 and 10 mt. Propellant mass fractions for each major phase of the EDL - Entry, Terminal Descent, and Hazard Avoidance - have been derived. An assessment of the entry conditions on the thermal protection system (TPS), currently in use for Dragon missions, has been made. And shows no significant stressors. A useful mass of 2.0 mt is provided and includes mass growth allowances for the MAV, the ERV, and mission unique equipment. We also report on alternate propellant options for the MAV and options for the ERV, including propulsion systems; crewed versus robotic retrieval mission; as well as direct Earth entry. International Planetary Protection Policies as well as verifiable means of compliance will have a large impact on any MSR mission design. We identify areas within our architecture where such impacts occur. This work shows that emerging commercial capabilities can be used to effectively integrated into a mission to achieve an important planetary science objective.

Mars Sample Return↗
NASA NTRS2011

Asteroid Return Mission Feasibility Study

This paper describes an investigation into the technological feasibility of finding, characterizing, robotically capturing, and returning an entire Near-Earth Asteroid (NEA) to the International Space Station (ISS) for scientific investigation, evaluation of its resource potential, determination of its internal structure and other aspects important for planetary defense activities, and to serve as a testbed for human operations in the vicinity of an asteroid. Reasonable projections suggest that several dozen candidates NEAs in the size range of interest (approximately 2-m diameter) will be known before the end of the decade from which a suitable target could be selected. The conceptual mission objective is to return an approximately 10,000-kg asteroid to the ISS in a total flight time of approximately 5 years using a single Evolved Expendable Launch Vehicle. Preliminary calculations indicate that this could be accomplished using a solar electric propulsion (SEP) system with high-power Hall thrusters and a maximum power into the propulsion system of approximately 40 kW. The SEP system would be used to provide all of the post-launch delta V. The asteroid would have an unrestricted Earth return Planetary Protection categorization, and would be curated at the ISS where numerous scientific and resource utilization experiments would be conducted. Asteroid material brought to the ground would be curated at the NASA Johnson Space Center. This preliminary study identified several areas where additional work is required, but no show stoppers were identified for the approach that would return an entire 10,000-kg asteroid to the ISS in a mission that could be launched by the end of this decade.

near Earth asteriods (NEA)↗
NASA NTRS2024

NASA's Capture, Containment, and Return System: Bringing Mars Samples to Earth

The Mars Sample Return (MSR) campaign is one of the most ambitious and complex planetary science exploration missions ever pursued. With the participation of NASA, ESA, and many industry partners, MSR aims to bring Martian rock and atmosphere samples to Earth with the goal of answering key questions about Mars’ geological, climatological and, potentially, biological evolution. To accomplish this ambitious goal, the MSR campaign relies on three distinct flight elements and a ground element. The Earth Return Orbiter mission that would host the Capture, Containment, and Return System (CCRS) is the last flight element of the trio. The mission would capture the orbiting sample in low Mars orbit (launched into orbit by another mission), contain it, and return it to Earth, landing at the Utah Test and Training Range. Since its early architecture, several changes were adopted by CCRS to improve overall payload efficiency and reduce mass. This paper will discuss the CCRS design, how the current CCRS architecture contributes to an improved mission concept, and the next critical steps of the mission toward its launch.

Mars mission↗
NASA NTRSDate not supplied

Mars Sample Return: Considerations for the Curation of Astromaterials from a Restricted Planet

The joint NASA/ESA Mars Sample Return (MSR) campaign is underway. The Perseverance Rover has already collected a returnable sample suite currently cached at Three Forks and the pairs to these samples are stored on the Rover with more compelling samples planned to be collected. The MSR collection would represent the most geologically diverse astromaterial collection ever returned and should provide information on topics ranging from Martian geological and biological history to Martian environmental hazards and in situ resource utilization to support potential human exploration. Although Jezero Crater and the surrounding area are not Mars special regions, the scientific opinion is that Mars as a whole is of significant interest to the process of chemical evolution and/or the origin of life. Therefore, due to possibility, however remote, that the samples could contain extraterrestrial life, MSR is classified as a Category V: Restricted Earth Return mission by the NASA Planetary Protection Office. As a result of this classification, a MSR Sample Receiving Facility (SRF) must not only provide a pristine environment to ensure samples are protected from terrestrial contamination for scientific investigations, but it must also provide high-containment to isolate the samples from Earth’s biosphere until the samples are deemed safe for release and/or sterilized.

Mars Sample Return↗
NASA NTRS2024

A High-Reliability Photoelectric Detection System for Mars Sample Return’s Orbiting Sample

The Mars Sample Return campaign is an endeavor of unprecedented technological complexity and coordination that attempts to answer fundamental questions about the habitability of Mars by returning the first samples of Martian material to Earth for analysis. The third mission in the campaign consists of the NASA-provided Capture, Containment, and Return System (CCRS) onboard the European Space Agency’s Earth Return Orbiter, which will retrieve the Orbiting Sample (OS) container from its orbit around Mars. Retrieving a passive sample container from a planetary orbit has never been attempted by any spacecraft and requires the development of new technology to succeed in this ambitious task. This paper introduces the high-reliability Capture Sensor Suite (CSS), a novel optical detection system that provides CCRS with the capability to autonomously detect the OS as it is captured. This article will discuss the challenges and requirements for the fault-tolerant design of the CSS.

planetary sampling↗
NASA NTRS2024

Enhancing the Protection of Shielded Thermal Protection Systems in Sample Return Spacecraft Against MMOD Impact

Sample return missions seek to collect samples from planets, moons, asteroids, and other planetary bodies and return them to earth for in-depth analysis. Backward planetary protection requirements are often in place for such missions to prevent the introduction of any extra-terrestrial material into the Earth’s biosphere, which could occur if a meteoroid or space debris particle were to damage a critical part of the returning spacecraft. The ability of a shielding system used to mitigate this damage risk is typically characterized by a ballistic limit equation (BLE), which predicts whether or not a protected system or structural element will sustain a critical failure due to a high-speed impact. In this paper, we develop a particle-impact-based BLE for the thermal protection system (TPS) of a sample return spacecraft that is protected by a multi-shock shield. The predictions of the BLE we develop for TPS failure are shown to be consistent with the predictions of hydrocode simulations.

Sample Return Spacecraft↗
DOE OSTI2019

Return flows from beaver ponds enhance floodplain-to-river metals exchange in alluvial mountain catchments

River to floodplain hydrologic connectivity is strongly enhanced by beaver- (Castor canadensis) engineered channel water diversions. The hydroecological impacts are wide ranging and generally positive, however, the hydrogeochemical characteristics of beaver-induced flowpaths have not been thoroughly examined. Using a suite of complementary ground- and drone-based heat tracing and remote sensing methodology we characterized the physical template of beaver-induced floodplain exchange for two alluvial mountain streams near Crested Butte, Colorado, USA. A flowpath-oriented perspective to water quality sampling allowed characterization of the chemical evolution of channel water diverted through floodplain beaver ponds and ultimately back to the channel in 'beaver pond return flows'. Subsurface return flow seepages were universally suboxic, while ponds and surface return flows showed a range of oxygen concentration due to in-situ photosynthesis and atmospheric mixing. Median concentrations of reduced metals: manganese (Mn), iron (Fe), aluminum (Al), and arsenic (As) were substantially higher along beaver-induced flowpaths than in geologically controlled seepages and upstream main channel locations. The areal footprint of reduced return seepage flowpaths were imaged with surface electromagnetic methods, indicating extensive zones of high-conductivity shallow groundwater flowing back toward the main channels and emerging at relatively warm bank seepage zones observed with infrared. Multiple-depth redox dynamics within one focused seepage zone showed coupled variation over time, likely driven by observed changes in seepage rate that may be controlled by pond stage. High-resolution times series of dissolved Mn and Fe collected downstream of the beaver-impacted reaches demonstrated seasonal dynamics in mixed river metal concentrations. Al time series concentrations showed proportional change to Fe at the smaller stream location, indicating chemically reduced flowpaths were sourcing Al to the channel. Overall our results indicated beaver-induced floodplain exchanges create important, and perhaps dominant, transport pathways for floodplain metals by expanding chemically-reduced zones paired with strong advective exchange.

58 GEOSCIENCES↗
DOE OSTI2022

Subduction, Underplating, and Return Flow Recorded in the Cycladic Blueschist Unit Exposed on Syros, Greece

Exhumed high-pressure/low-temperature (HP/LT) metamorphic rocks provide insights into deep (~20–70 km) subduction interface dynamics. On Syros Island (Cyclades, Greece), the Cycladic Blueschist Unit preserves blueschist-to-eclogite facies oceanic- and continental-affinity rocks that record the structural and thermal evolution linked to Eocene subduction. Despite decades of research, the metamorphic and deformation history (P-T-D) and timing of subduction and exhumation are matters of ongoing discussion. We suggest that Syros comprises three coherent tectonic slices and that each slice underwent subduction, underplating, and syn-subduction return flow along similar P-T trajectories, but at progressively younger times. Subduction and exhumation are distinguished by lineations and ductile fold axis orientations, and are kinematically consistent with previous studies that document top-to-the-S-SW shear (prograde-to-peak subduction), top-to-the-NE shear (blueschist facies exhumation), and then E-W coaxial stretching (greenschist facies exhumation). Amphibole zonations record cooling during decompression, indicating return flow above a cold slab. Multi-mineral Rb-Sr isochrons and compiled metamorphic geochronology show that the three slices record distinct stages of peak subduction (53–52, ~50, and 45 Ma) that young with structural depth. Retrograde blueschist and greenschist facies fabrics span ~50–40 and ~43–20 Ma, respectively, and also young with structural depth. Synthesized data sets support a revised tectonic framework for Syros, involving subduction of structurally distinct coherent slices and simultaneous return flow of previously accreted tectonic slices in the subduction channel shear zone. Distributed, ductile, dominantly coaxial return flow in an Eocene-Oligocene subduction channel proceeded at rates of ~1.5–5 mm/yr and accommodated ~80% of the total exhumation of this HP/LT complex.

58 GEOSCIENCES↗
DOE OSTI2015

Numerical study on Rayleigh-Taylor instabilities in the lightning return stroke

The Rayleigh-Taylor (R-T) instabilities are important hydrodynamics and magnetohydrodynamics (MHD) phenomena that are found in systems in high energy density physics and normal fluids. The formation and evolution of the R-T instability at channel boundary during back-flow of the lightning return stroke are analyzed using the linear perturbation theory and normal mode analysis methods, and the linear growth rate of the R-T instability in typical condition for lightning return stroke channel is obtained. Then, the R-T instability phenomena of lightning return stroke are simulated using a two-dimensional Eulerian finite volumes resistive radiation MHD code. The numerical results show that the evolution characteristics of the R-T instability in the early stage of back-flow are consistent with theoretical predictions obtained by linear analysis. The simulation also yields more evolution characteristics for the R-T instability beyond the linear theory. The results of this work apply to some observed features of the return stroke channel and further advance previous theoretical and experimental work.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2018

Estimation of emigration, return migration, and transit migration between all pairs of countries

We propose a method for estimating migration flows between all pairs of countries that allows for decomposition of migration into emigration, return, and transit components. Current state-of-the-art estimates of bilateral migration flows rely on the assumption that the number of global migrants is as small as possible. We relax this assumption, producing complete estimates of all between-country migration flows with genuine estimates of total global migration. We find that the total number of individuals migrating internationally has oscillated between 1.13 and 1.29% of the global population per 5-year period since 1990. Return migration and transit migration are big parts of total migration; roughly one of four migration events is a return to an individual’s country of birth. In the most recent time period, we estimate particularly large return migration flows from the United States to Central and South America and from the Persian Gulf to south Asia.

Science & Technology - Other Topics↗
NASA NTRS1973

Electric field intensity of the lightning return stroke.

From an examination of about 1000 electric field wave forms produced by lightning return strokes in 16 storms at distances between 20 and 100 km from an observation site at the Kennedy Space Center, Florida, a typical return stroke current wave form is derived. For this current wave form, the electric field intensity at distances between 0.5 and 100 km is computed for three values of return stroke velocity. The resultant curves for close lightning are compared with measured field wave forms. The transmission line return stroke model is used in all calculations since, as discussed, the Bruce-Golde model cannot account for the observed electric field characteristics.

Uman, M. A.↗
NASA NTRS1974

On the petrological, geochemical, and geophysical characterization of a returned Mars surface sample and the impact of biological sterilization on the analyses

A study was conducted: to identify those experiments that could and should be done on a returned Martian sample in order to characterize its inorganic properties; to evaluate, insofar as can be done, the effects of potential biological sterilization of the sample by heating prior to its return; to identify particular analytical techniques needing further improvement in order to make optimum use of a returned sample; and to identify experiments to be done on simulants, with and without sterilization, that better define the limits of information available about the planet from analyses of returned samples.

Source record↗
NASA NTRS1975

Mars sample return by orbital rendezvous

The return of Mars surface samples by the orbital rendezvous mode would require smaller, lighter vehicles than the direct return mode and would limit the exposure of the earth return systems to possible contamination by Martian biota. The reference mission considered would use a single Titan IIIE/Centaur launch vehicle, carry a 1 kg sample, and be launched in late 1981. The spacecraft would consist of an orbiter, a Mars lander, a Mars ascent vehicle, an earth return vehicle, and an earth entry capsule. The Mars ascent vehicle is the only all-new vehicle required, the others being derived from Viking and other programs. A key consideration is the feasibility of automatic rendezvous and sample transfer between the ascent vehicle and orbiter in Mars orbit. The maneuvers required and the maneuver algorithm developed in a NASA feasibility study are described in detail. The possibility of international cooperation on a Mars orbital rendezvous mission is discussed.

Moore, J. W.↗