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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 343 records · Page 19
All sourcesNASA NTRSDOE OSTI
NASA NTRS1982

Observations near the magnetopause at the onset of the July 29, 1977, sudden storm commencement

Characteristics of an earthward movement of the magnetopause caused by the arrival of an interplanetary shockwave are derived from data acquired by the GEOS 1 spacecraft on July 29, 1977. Data were taken on electric field, plasma, magnetic field, energetic particles, and composition before, during, and after leaving the magnetopause. Correlative examinations were made with information gathered by the IMP 7, IMP 8, and ATS 6 satellites. The magnetopause was found to move earthward at 95 km/sec and had a thickness of 500 km. The existence of three different regions is postulated, one with field lines connected directly to the earth, the magnetosphere, a second, the magnetosheath, with no magnetic field line connection to the earth, and a thir; with one end of the field lines connected to the earth and the other to the interplanetary medium, called the transition region.

Knott, K.↗
NASA NTRS1984

The magnetic activity of sunlike stars

The solar magnetic field, when carried into interplanetary space by the solar wind, creates changes in the earth's magnetosphere and variations in the galactic cosmic ray particle flux incident on the earth's upper atmosphere. Observational data accumulated over several centuries have indicated that the solar magnetism exists and varies in a globally organized pattern that is coupled to the sun's rotation. Wilson (1966, 1981) has demonstrated that analogs of solar activity exist and can be studied in many other dwarf stars, so that knowledge of the precise rates of rotation of stars under investigation can increase understanding of the origins of solar activity in particular and stellar activity in general.

Vaughan, A. H.↗
NASA NTRS2011

Earth Orbit Raise Design for the Artemis Mission

The Artemis mission is an extension of the Themis mission. The Themis mission1 consisted of five identical spacecraft in varying sized Earth orbits designed to make simultaneous measurements of the Earth's electric and magnetic environment. Themis was designed to observe geomagnetic storms resulting from solar wind's interaction with the Earth's magnetosphere. Themis was meant to answer the age old question of why the Earth's aurora can change rapidly on a global scale. The Themis spacecraft are spin stabilized with 20 meter long electric field booms as well as several shorter magnetometer booms. The goal of the Artemis2 mission extension is to deliver the field and particle measuring capabilities of two of the Themis spacecraft to the vicinity of the Moon. The Artemis mission required transferring two Earth orbiting Themis spacecraft on to two different low energy trans-lunar trajectories ultimately ending in lunar orbit. This paper describes the processes that resulted in successful orbit raise designs for both spacecraft.

spin stablized↗
NASA NTRS1980

Utilization of multi-body trajectories in the Sun-Earth-Moon system

An overview of three uncommon trajectory concepts for space missions in the Sun-Earth-Moon System is presented. One concept uses a special class of libration-point orbits called 'halo orbits.' It is shown that members of this orbit family are advantageous for monitoring the solar wind input to the Earth's magnetosphere, and could also be used to establish a continuous communications link between the Earth and the far side of the Moon. The second concept employs pretzel-like trajectories to explore the Earth's geomagnetic tail. These trajectories are formed by using the Moon to carry out a prescribed sequence of gravity-assist maneuvers. Finally, there is the 'boomerang' trajectory technique for multiple-encounter missions to comets and asteroids. In this plan, Earth-swingby maneuvers are used to retarget the original spacecraft trajectory. The boomerang method could be used to produce a triple-encounter sequence which includes flybys of comets Halley and Tempel-2 as well as the asteroid Geographos.

Farquhar, R. W.↗
NASA NTRS1981

Environmental effects and large space systems

When planning large scale operations in space, environmental impact must be considered in addition to radiation, spacecraft charging, contamination, high power and size. Pollution of the atmosphere and space is caused by rocket effluents and by photoelectrons generated by sunlight falling on satellite surfaces even light pollution may result (the SPS may reflect so much light as to be a nuisance to astronomers). Large (100 Km 2) structures also will absorb the high energy particles that impinge on them. Altogether, these effects may drastically alter the Earth's magnetosphere. It is not clear if these alterations will in any way affect the Earth's surface climate. Large structures will also generate large plasma wakes and waves which may cause interference with communications to the vehicle. A high energy, microwave beam from the SPS will cause ionospheric turbulence, affecting UHF and VHF communications. Although none of these effects may ultimately prove critical, they must be considered in the design of large structures.

Garrett, H. B.↗
NASA NTRS1989

A model of global convection in Jupiter's magnetosphere

Voyager observations of Jupiter's magnetosphere are compared with the planetary wind model in which corotation must break down outside some Alfven critical radius and a centrifugally driven wind outflow must develop. It is found that the model does not agree with the observations. A new global convection model for the Jovian magnetosphere is proposed, based on models of quasi-stationary plasma convection in the earth's magnetosphere. The model predicts a substantial dawn-dusk asymmetry in the structure, dynamics, and plasma composition of the magnetopause and magnetosheath. The model also predicts a region of cross-tail flow in the nightside plasma sheet containing a substantial admixture of solar wind plasma.

Cheng, A. F.↗
NASA NTRS1991

Origins of magnetospheric plasma

A review is given of recent (1987-1990) progress in understanding of the origins of plasmas in the earth's magnetosphere. In counterpoint to the early supposition that geomagnetic phenomena are produced by energetic plasmas of solar origin, 1987 saw the publication of a provocative argument that accelerated ionospheric plasma could supply all magnetospheric auroral and ring current particles. Significant new developments of existing data sets, as well as the establishment of entirely new data sets, have improved the ability to identify plasma source regions and to track plasma through the magnetospheric system of boundary layers and reservoirs. These developments suggest that the boundary between ionospheric and solar plasmas, once taken to lie at the plasmapause, actually lies much nearer to the magnetopause. Defining this boundary as the surface where solar wind and ionosphere contribute equally to the plasma, it is referred to herein as the 'geopause'. It is now well established that the infusion of ionospheric O(+) plays a major role in the storm-time distention of the magnetotail and inflation of the inner magnetosphere. After more than two decades of observation and debate, the question remains whether magnetosheric are protons of solar or terrestrial origin.

Moore, Thomas E.↗
NASA NTRS1994

Flank solar wind interaction

In this report we will summarize the results of the work performed under the 'Flank Solar Wind Interaction' investigation in support of NASA's Space Physics Guest Investigator Program. While this investigation was focused on the interaction of the Earth's magnetosphere with the solar wind as observed by instruments on the International Sun-Earth Explorer (ISEE) 3 spacecraft, it also represents the culmination of decades of research performed by scientists at TRW on the rich phenomenology of collisionless shocks in space.

Moses, Stewart L.↗
NASA NTRS2009

Extended Kalman Filter for MMS State Estimation

The Magnetospheric MultiScale Mission is a four spacecraft formation flying mission designed to study the Earth s magnetosphere. The spacecraft fly in highly elliptical orbits, forming a tetrahedron at apogee. Each spacecraft spins at 3 RPM and is equipped with a star scanner, slit sun sensor, and accelerometer. The purpose of this work is to develop an Extended Kalman Filter to simultaneously estimate the attitude, angular velocity, angular acceleration, and center of mass of each spacecraft.

Markley, F. Landis↗
NASA NTRS2021

Magnetospheric Multi Scale (MMS) Patching Story for DARPA AMP Collaboration

NASA’s Magnetospheric Multiscale (MMS) spacecraft are part of a robotic space mission that studies the Earth's magnetosphere. Launched in March 2015, MMS consists of four identical spacecraft that fly in a tetrahedral formation. The spacecraft gather information about the microphysics of magnetic reconnection including turbulence and energetic particle acceleration ⁠—processes common in many astrophysical plasmas.

Gilberto Alves Vicente↗
NASA NTRS1977

The solar-terrestrial observatory as a major module of a space station

The solar-terrestrial environment is a dynamic, tightly coupled system in which variable solar energy is transmitted through electromagnetic radiation and the solar wind to the earth's magnetosphere and atmosphere. The constantly changing solar input and the continuous redistribution of energy near the earth combine to determine the characteristics of our global environment. An understanding and subsequent management of this environment will require a coordinated set of observations of solar processes and the accompanying magnetospheric and atmospheric responses. A major element in this observational plan should be a Solar-Terrestrial Observatory module of a manned Space Station in which instruments and experimental techniques developed during short-duration Spacelab flights will be applied to extended missions in both low-altitude and geosynchronous orbits.

Chappell, C. R.↗
NASA NTRS1984

Particle transport in planetary magnetospheres

Particle energization in Earth's and Jupiter's magnetospheres is discussed. Understanding of the large scale magnetic and electric fields in which charged particles move is reviewed. Orbit theory in the adiabatic approximation is sketched. General conditions for adiabatic breakdown at each of three levels of periodicity are presented. High energy losses and lower energy sources argue for the existence of magnetospheric accelerations. Nonadiabatic acceleration processes are mentioned. Slow diffusive energization by particle interactions with electromagnetic fluctuations is outlined. This mechanism seems adequate at Earth but, operating alone, is unconvincing for Jupiter. Adding spatial diffusion in the radially distended Jovian magnetodisk may resolve the difficulty.

Birmingham, T. J.↗
NASA NTRS1975

Preliminary interpretation of plasma electron observations at the third encounter of Mariner 10 with Mercury

Plasma electron count observations made during the first and third encounters of Mariner 10 with Mercury (i.e., during Mercury I and III) are reported. They provide detailed information on the magnetosphere of Mercury, especially those from Mercury III. A low-flux region was observed about closest approach (CA) of Mercury III, whereas no such region was detected by the lower-latitude Mercury I; a hot plasma sheet was measured on the outgoing (and near-equator) trajectory of Mercury I, while only cool plasma sheets were observed in the magnetosphere by Mercury III. Findings are similar, on a reduced scale, to models of the earth's magnetosphere and magnetosheath.

Hartle, R. E.↗
NASA NTRS1986

Magnetospheric energetic ions from the earth's ionosphere

In the decade and a half since the initial discovery that the earth's own ionosphere could at times contribute measurably to the hot plasma in the magnetosphere, significant progress has been made in both current knowledge and understanding of this connection. It is now known that ions of ionospheric origin are found in all major regions of the magnetosphere and at its boundaries. The source region in the ionosphere and the acceleration and transport processes involved in coupling the cold ionospheric plasma to the hot magnetospheric plasma are complex and variable. The large scale morphology of the ionospheric outflow and its distribution throughout the magnetosphere is now understood and progress is being made in the understanding of the fundamental physical processes involved. In this paper attention is given to the large scale morphology and current understanding of the sources for ionospheric ions found in various regions of the magnetosphere and their transport.

Shelley, E. G.↗
NASA NTRS2005

The Effects of Thrust Uncertainty and Attitude Knowledge Errors on the MMS Formation Maintenance Maneuver

The Magnetospheric Multiscale (MMS) Mission will use a formation of four spinning spacecraft to study the Earth s magnetosphere. The science objectives of MMS require a near-regular tetrahedron formation to be maintained with side lengths ranging from ten kilometers to several thousand kilometers at orbit apogee. To reduce spacecraft complexity and cost, the current mission concept assumes MMS can achieve its formation goals through open-loop orbit control from the ground, rather than in-flight, closed-loop formation control that has been the subject of recent study. Significant analysis has been performed to provide optimal reference orbit and relative orbit designs. However, the feasibility of achieving these orbits, and maintaining them for an extended period of time in the presence of real world errors and perturbations has not been investigated. In particular, attitude knowledge and control errors, which may have a negligible effect on orbit control for conventional missions with spinning spacecraft, can contribute significant errors to the MMS orbits. In this work, a 6 degree-of-freedom (DOF) simulation is developed and used to analyze the effects of realistic errors on formation maintenance maneuver accuracy. Several realistic considerations including a finite-burn model, attitude perturbations, and thrust uncertainty are studied. The primary objective is to quantify the effects of realistic attitude and orbit control, knowledge, and actuator errors on the formation geometry by observing representative maneuver errors of a single spacecraft.

Tsai, Dean C.↗
NASA NTRS2009

GPS Navigation for the Magnetospheric Multi-Scale Mission

In 2014. NASA is scheduled to launch the Magnetospheric Multiscale Mission (MMS), a four-satellite formation designed to monitor fluctuations in the Earth's magnetosphere. This mission has two planned phases with different orbits (1? x 12Re and 1.2 x 25Re) to allow for varying science regions of interest. To minimize ground resources and to mitigate the probability of collisions between formation members, an on-board orbit determination system consisting of a Global Positioning System (GPS) receiver and crosslink transceiver was desired. Candidate sensors would be required to acquire GPS signals both below and above the constellation while spinning at three revolutions-per-minute (RPM) and exchanging state and science information among the constellation. The Intersatellite Ranging and Alarm System (IRAS), developed by Goddard Space Flight Center (GSFC) was selected to meet this challenge. IRAS leverages the eight years of development GSFC has invested in the Navigator GPS receiver and its spacecraft communication expertise, culminating in a sensor capable of absolute and relative navigation as well as intersatellite communication. The Navigator is a state-of-the-art receiver designed to acquire and track weak GPS signals down to -147dBm. This innovation allows the receiver to track both the main lobe and the much weaker side lobe signals. The Navigator's four antenna inputs and 24 tracking channels, together with customized hardware and software, allow it to seamlessly maintain visibility while rotating. Additionally, an extended Kalman filter provides autonomous, near real-time, absolute state and time estimates. The Navigator made its maiden voyage on the Space Shuttle during the Hubble Servicing Mission, and is scheduled to fly on MMS as well as the Global Precipitation Measurement Mission (GPM). Additionally, Navigator's acquisition engine will be featured in the receiver being developed for the Orion vehicle. The crosslink transceiver is a 1/4 Watt transmitter utilizing a TDMA schedule to distribute a science quality message to all constellation members every ten seconds. Additionally the system generates one-way range measurements between formation members which is used as input to the Kalman filter. In preparation for the MMS Preliminary Design Review (PDR), the Navigator was required to pass a series of Technology Readiness Level (TRL) tests to earn the necessary TRL-6 classification. The TRL-6 level is achieved by demonstrating a prototype unit in a relevant end-to-end environment. The IRAS unit was able to meet all requirements during the testing phase, and has thus been TRL-6 qualified

Bamford, William↗
NASA NTRS1976

Field-aligned currents in the Jovian magnetosphere - Pioneer 10 and 11

Field-aligned currents, which are known to play an important role in the dynamics of the earth's magnetosphere, would also be expected to flow in the Jovian magnetosphere during magnetically active periods. Such currents are difficult to observe largely because of their limited spatial extent and intermittent nature, but on the Pioneer 11 inbound pass to Jupiter on day 336, 1800 GRT, near the L shell of Ganymede, the helium vector magnetometer recorded a structured perturbation with the characteristic signature of a field-aligned current. No analogous structure was found on a similar Pioneer 10 inbound pass (day 337, 1200 GRT). The perturbation could have been caused by turbulence with the wake of Ganymede through which the spacecraft was moving or the perturbation could represent the first observation of a Jovian substorm. The observations are discussed in terms of both models, and difficulties are examined.

Kivelson, M. G.↗
NASA NTRS1986

A statistical study of plasma sheet dynamics using ISEE 1 and 2 energetic particle flux data

Plasma sheet dynamics during substorms are studied by analyzing 461 cases of transient dropout events of the 1.5 and 6-keV particle fluxes detected by ISEE 1 and 2 satellites. The instruments for detecting low- and high-energy particles are described. The spatial distribution of flux dropout events, and the events' relationship to magnetospheric activity level are examined. Substorm events without observed flux dropout events are investigated. The data reveal that the flux dropout distribution is isotropic, between 12-23 earth radii, and is present in the entire nightside plasma sheet; and the substorms without flux dropout are more frequent near earth and magnetospheric flanks. It is observed that tailward of 12 earth radii the flux dropout events and substorms without flux dropout are similar. The Chao et al. (1977) MHD rarefaction wave propagation model and the Hones (1973, 1980) near-tail, X-type magnetic neutral line formation model are discussed and compared to the experimental data. It is noted that neither model explains the plasma sheet dynamics observed.

Dandouras, J.↗