Search NASA⌕ Search

SEARCH · Search NASA

Results for “observer spacecraft”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 91 records · Page 5
All sourcesNASA NTRSDOE OSTI
NASA NTRS1974

Corotating particle fluxes observed with the Pioneer 7 and IMP 4 spacecraft

Observations are reported of the time development of 17-MeV proton fluxes in four corotating particle streams during the five days required for corotation from Pioneer 7, about 70 E of earth in 1968, to IMP-4 at earth. The azimuthal width of the particle streams was observed to remain constant over the five days. Assuming either continuous or impulsive injection of particles at the sun, this observation is shown to imply that the azimuthal diffusion coefficient was significantly less than the value derived from recent solar flare observations (McKibben, 1972).

Mckibben, R. B.↗
NASA NTRS1983

Earth observation system: Spacecraft design

The Earth Observation Satellite (EOS) was a study funded by NASA Langley Research Center. The study was a system investigation of the total spacecraft integration with its major subsystems and sensors. Mission optimization and ranking using various sensors was also an objective of the contract. Integrating the spacecraft and major subsystems with the large microwave radiometer was done, essentially making the radiometer a free-flyer without an external spacecraft. Another program objective was to provide design and analysis data on microwave radiometer satellites augmented with additional Earth, ocean, and atmospheric sensors. A top-down systems approach resulted in a detailed design integrating subsystems and sensors into the microwave support structure. An important objective of the program was to identify technology needs for Earth observation satellites. The definition and understanding of these design drivers are critical in order to set priorities for future EOS work.

Herbert, J. J.↗
NASA NTRS2002

Science Planning for Multi-Spacecraft Coordinated Observations

Fulfilling the promise of an era of great observatories, NASA now has more than three space-based astronomical telescopes operating in different wavebands. This situation provides astronomers with a unique opportunity to simultaneously observe with multiple observatories. Yet scheduling multiple observatories simultaneously is highly inefficient when compared to single observatory observations. Thus, programs using multiple observatories are limited not due to scientific restrictions, but due to operational inefficiencies. Each year, a number of proposals are accepted by a space-based observatory for conduction of astronomical observations and gathering of science data for the study of galactic events. Since each space-based observatory uses a set of instruments designed to operate in specific energy regions, most such studies are conducted by submitting observation proposals to multiple observatories, with requests to coordinate among themselves. To assure that the proposed observations can be scheduled, each observatory's staff has to check that the observations are valid and meet all the constraints for their own observatory; in addition, they have to verify that the observations satisfy the constraints of the other observatories. Thus, coordinated observations require painstaking manual collaboration among the observatory staff at each observatory. In order to exploit new paradigms for observatory operation, the Goddard Space Flight Center's Advanced Architectures and Automation Branch has developed a prototype tool called the Visual Observation Layout Tool (VOLT). The main objective of VOLT is to provide a visual tool to automate the science planning of coordinated observations for multiple spacecraft, as well as to increase the scheduling probability of observations. However, VOLT is also useful for single observatory planning to optimize observatory control. Three space-based missions are interested in using VOLT (the Hubble Space Telescope, the Chandra X-Ray Observatory, and the Far Ultraviolet Spectroscopic Explorer). The VOLT team members have collaborated with these missions to gather requirements and obtain feedback on their mission planning processes. VOLT has been developed as a cross-platform Java client application for use by scientists and observatory science planning staff to visualize scheduling options and constraints. It also supports a lightweight graphical user interface for remote viewing via a Web front end. Additionally, it uniquely supports the ability to interact with multiple, diverse scheduling packages in order to determine windows of opportunity for observations and visually portray the constraints of each observation request. VOLT enables science data capture scenarios which are currently either impossible, or which require extensive time and manpower to coordinate amongst multiple observatories. it supports early detection of planning conflicts by generating coordinated solutions based on observatory schedulability and constraints. The project development approach has included frequent prototype demonstrations to our interested missions to obtain feedback after each release of the software. We will present an overview of our lessons learned in infusing the VOLT tool into the operations of the missions we have collaborated with and a brief demonstration of the software.

Maks, Lori↗
NASA NTRS1989

Spatial variation and evolution of heliospheric sector structure

The magnetic sector polarity at the sun and in the IMF was surveyed during about three quarters of sunspot cycle 21 using ground-based photospheric magnetic field observations and spacecraft observations, including Voyagers 1 and 2 and Pioneer Venus Orbiter data. The location of the heliospheric current sheet near the sun throughout the period 1977-1985 is calculated. The large-scale magnetic polarity structure was in almost continuous evolution throught this period. IMF polarity patterns derived from spacecraft data are compared with the pattern observed at the sun, showing that sector pattern stability decreases with increasing heliocentric distance.

Behannon, K. W.↗
NASA NTRS1994

The flaring of the Martian magnetotail observed by the Phobos 2 spacecraft

Spacecraft observations from the Earth's magnetotail show that the flaring angle depends on the downtail distance, the upstream solar wind dynamic pressure and the B(sub z) component of the interplanetary magnetic field (1993). Measurements from the Phobos 2 spacecraft along a circular orbit at 2.8 Mars radii allow a similar study of the Mars magnetotail. Under the assumption that the magnetic pressure in the Martian tail lobes is much greater than the plasma pressure in the lobe, we use the pressure balance condition between the tail lobe magnetic pressure and the normal component of the solar wind pressure to infer the angle at which the tail magnetopause flares. As in the case of the terrestrial magnetotail, the flaring angle of Mars tail depends on the solar wind dynamic pressure, but this angle (at 2.5 R(sub M)) is about one half of the terrestrial value (at 17 R(sub E)). The median inferred flaring angle is about 13 deg.

Zhang, T.-L.↗
NASA NTRS1998

Observations of Spacecraft Targets, Unusual Asteroids, and Targets of Opportunity

Obtain physical and astrometric observations of: (1) spacecraft targets to support mission operations; (2) known asteroids with unusual orbits to help determine their origin; and (3) newly discovered minor planets (including both asteroids and comets) that represent a particular opportunity to add significant new knowledge of the Solar System.

Tholen, David J.↗
NASA NTRS2024

Azimuthal Size Scales of Solar Wind Periodic Density Structures

Periodic Density Structures (PDSs) are quasi-periodic variations of solar wind density ranging from a few minutes to a few hours. PDSs advect with the solar wind and have radial length scales (Lx) of tens to several thousand Mm, thus belonging to the class of “mesoscale structures”. Current interplanetary multi-spacecraft observations are not at spatial separations capable of directly measuring the 3D size scale of PDSs or other mesoscale structures. Instead, previous investigations estimated characteristic spatial scales in solar wind parameters using cross-correlation and/or coherence analysis applied to multi-spacecraft observations. For solar wind density and interplanetary magnetic field (IMF) intensity, the reported size scales perpendicular to the Sun-Earth line (Ly) ranged between ≈30 and ≈200 Earth Radii (RE). Here, we implemented a similar approach on the same parameters but focused on high density slow solar wind intervals with PDSs observed by the Wind and ARTEMIS-P1 spacecraft. Additionally, this is the first statistical study of the IMF intensity periodicities in relation to PDSs. We identified intervals in which the two spacecraft observed the same periodicity obtaining two PDS groups based on their radial length scale: Lx1 ≈86RE and Lx2 ≈35RE. Then, we classified the events based on the periodic variations’ coherence level. Reproducing the results with simulations of the PDSs’ transit, we inferred the Ly order of magnitudes for the two PDS groups: Ly1 ≈340RE and Ly2 ≈187RE. Knowing the PDSs’ size scales is fundamental to constrain models aimed at reproducing these structures and is critical to better understand the PDS-magnetosphere coupling.

Interplanetary physics↗
NASA NTRS2002

High-Latitude Magnetic Reconnection in Sub-Alfvenic Flow as Observed by Interball Tail on 29 May 1996

The Interball/Tail spacecraft crossed the high latitude magnetopause near the cusp region under stable northward IMF conditions on 29 May 1996, with magnetic local time and magnetic latitude approx. 7.3 hours, approx. 65.4 degrees, respectively. The Interball Tail spacecraft observed quasi-steady reconnection and a relatively stable reconnection site at high latitudes. Observed sunward plasma flow and tangential stress balance indicated that reconnection occurred poleward of the magnetic cusp, above the spacecraft location. The spacecraft observed sub-alfvenic flow in the magnetosheath region adjacent to the magnetopause current layer near the reconnection site indicating that the reconnection site may have moved in the sunward direction. These observations suggest that the region of sub-alfvenic flow and stable, quasi-steady reconnection extend to very high latitudes under northward IMF conditions which is not consistent with the gas dynamic model predictions.

Smirnov, V. N.↗
NASA NTRS2016

Impacts of Spontaneous Hot Flow Anomalies on the Magnetosheath and Magnetopause

Spacecraft observations and global hybrid (kinetic ions and fluid electrons) simulations have demonstrated that ion dissipation processes at the quasi-parallel bow shock are associated with the formation of structures called spontaneous hot flow anomalies (SHFAs). Previous simulations and recent spacecraft observations have also established that SHFAs result in the formation of magnetosheath filamentary structures(MFS). In this paper we demonstrate that in addition to MFS, SHFAs also result in the formation of magnetos heath cavities that are associated with decreases in density, velocity, and magnetic field and enhancements in temperature. We use the results of a global MHD run to determine the change in the magnetosheath properties associated with cavities due to ion kinetic effects. The results also show the formation of regions of high flow speed called magnetosheath jets whose properties as a function of solar wind Mach number are described in this study. Comparing the properties of the simulated magnetosheath cavities and jets to past spacecraft observations provides good agreement in both cases. We also demonstrate that pressure variations associated with cavities and SHFAs in the sheath result in a continuous sunward and anti sunward magnetopause motion. This result is consistent with previous suggestions that SHFAs may be responsible for the generation of ion cyclotron waves and precipitation of ring current protons in the outer magnetosphere.

Omidi, N.↗
NASA NTRS2002

Science Goal Driven Observing and Spacecraft Autonomy

Spacecraft autonomy will be an integral part of mission operations in the coming decade. While recent missions have made great strides in the ability to autonomously monitor and react to changing health and physical status of spacecraft, little progress has been made in responding quickly to science driven events. For observations of inherently variable targets and targets of opportunity, the ability to recognize early if an observation will meet the science goals of a program, and react accordingly, can have a major positive impact on the overall scientific returns of an observatory and on its operational costs. If the onboard software can reprioritize the schedule to focus on alternate targets, discard uninteresting observations prior to downloading, or download a subset of observations at a reduced resolution, the spacecraft's overall efficiency will be dramatically increased. The science goal monitoring (SGM) system is a proof-of-concept effort to address the above challenge. The SGM will have an interface to help capture higher level science goals from the scientists and translate them into a flexible observing strategy that SGM can execute and monitor. We are developing an interactive distributed system that will use on-board processing and storage combined with event-driven interfaces with ground-based processing and operations, to enable fast re-prioritization of observing schedules, and to minimize time spent on non-optimized observations.

Koratkar, Amuradha↗
NASA NTRS2002

Science Goal Driven Observing and Spacecraft Autonomy

Spacecraft autonomy will be an integral part of mission operations in the coming decade. While recent missions have made great strides in the ability to autonomously monitor and react to changing health and physical status of spacecraft, little progress has been made in responding quickly to science driven events. For observations of inherently variable targets and targets of opportunity, the ability to recognize early if an observation will meet the science goals of a program, and react accordingly, can have a major positive impact on the overall scientific returns of an observatory and on its operational costs. If the onboard software can reprioritize the schedule to focus on alternate targets, discard uninteresting observations prior to downloading, or download a subset of observations at a reduced resolution, the spacecraft's overall efficiency will be dramatically increased. The science goal monitoring (SGM) system is a proof- of-concept effort to address the above challenge. The SGM will have an interface to help capture higher-level science goals from the scientists and translate them into a flexible observing strategy that SGM can execute and monitor. We are developing an interactive distributed system that will use on-board processing and storage combined with event-driven interfaces with ground-based processing and operations, to enable fast re-prioritization of observing schedules, and to minimize time spent on non-optimized observations. This paper will focus on our strategy for developing SGM and the technical challenges that we have encountered. We will discuss the SGM architecture as it applies to the proposed MIDEX-class mission Kronos. However, the architecture and interfaces will also be designed for easy adaptability to other observing platforms, including ground-based systems and to work with different scheduling and pipeline processing systems.

Jones, Jeremy↗
NASA NTRS1994

Nickel cadmium battery operations on-orbit: Trials, tribulations, and success on the Upper Atmosphere Research Satellite

The Upper Atmosphere Research Satellite (UARS), designed, built, integrated, tested, and operated by NASA and Martin Marietta is a low-Earth orbiting, Earth-observing spacecraft which was launched via Space Shuttle Discovery on September 12, 1991 and deployed three days later. The Modular Power Subsystem (MPS) onboard the satellite is equipped with three NASA Standard 50 Ampere-hour (Ah) nickel-cadmium (NiCd) batteries. McDonnell Douglas Electronics Systems Company fabricated the MPS, and batteries from Gates Aerospace Batteries cells. Nominal battery performance was achieved for the first four months of spacecraft operation. First evidence of anomalous battery performance was observed in January 1992, after the first maximum beta angle (low Depth of Discharge) period. Since then, the Flight Operations Team (FOT), under the direction of Goddard Space Flight Center's UARS Project and Space Power Application Branch, has monitored and managed battery performance by adjusting solar array offset angle, conducting periodic deep discharge, and controlling battery recharge ratio. This paper covers a brief overview of the UARS, the FOT's operational battery management, and the observed spacecraft battery performance.

Rao, Gopalakrishna M.↗
NASA NTRS2018

MODIS and VIIRS On-Orbit Calibration and Characterization Using Observations from Spacecraft Pitch Maneuvers

Two MODIS instruments (Terra and Aqua) and two VIIRS instruments (S-NPP and JPSS-1) are currently operated inspace, continuously making global earth observations in the spectral range from visible (VIS) to long-wave infrared(LWIR). These observations have enabled a broad range of environmental data records to be generated and distributed insupport of both operational and scientific community. Despite extensive pre-launch calibration and characterizationperformed for both MODIS and VIIRS instruments and routine on-orbit calibration activities carried out using their onboardcalibrators (OBC), various spacecraft maneuvers have also been designed and implemented to further enhance thesensor on-orbit calibration and data quality. This paper focuses on the use of observations made during spacecraft pitchmaneuvers of MODIS and VIIRS in support of their on-orbit characterization of thermal emissive bands (TEB) responseversus scan-angle (RVS). In the case of Terra MODIS, lunar observations made from instrument nadir view duringspacecraft pitch maneuvers are used to compare with that made regularly through instrument space view (SV) port toevaluate on-orbit changes in RVS and band-to-band registration (BBR) for the reflective solar bands (RSB). In additionto results derived from spacecraft pitch maneuvers performed for MODIS and VIIRS, discussion is provided on theadvantages, challenges, and lessons for future considerations and improvements.

Xiong, Xiaoxiong↗
NASA NTRS1999

A Search for Simultaneous Optical Counterparts of Gamma-Ray Bursts (LOTIS: Livermore Optical Transient Imaging System)

Under this grant the UC Berkeley PI, K. Hurley, joined the LOTIS collaboration. His task was to provide precise localization data on cosmic gamma-ray bursts, so that the LOTIS automated camera data could be searched more efficiently for evidence of optical emission from gamma-ray burst sources. This was accomplished. A program is now in place which automatically sends Interplanetary Network data on bursts via e-mail to H.S. Park, for every burst detected by the GRB experiment aboard the Ulysses spacecraft (for which K. Hurley is the P.I.). The data consist either of triangulation annuli (obtained when just two spacecraft observe the burst) or error boxes (when three widely separated spacecraft observe it). These define a locus of possible burst positions. The annuli intersect the large error circles of the CGRO-BATSE experiment, and reduce their areas by a factor of approximately 25 or more. The error boxes reduce the areas by factors of several hundred. This in turn reduces the area which must be searched for an optical counterpart. No such counterparts have been observed to date by the LOTIS experiment, but several interesting upper limits have been obtained.

Park, H.-S.↗
NASA NTRS1998

Determination of Particle Sources for a Geotail Distribution Function Observed on May 23, 1995

On May 23, 1995, the Comprehensive Plasma Instrumentation (CPI) onboard the Geotail spacecraft observed a complex and structured ion distribution function near the magnetotail midplane at x approximately -10 R(sub E). On the same day, the Wind spacecraft observed a very high density (approximately 40/cubic cm) solar wind and an interplanetary magnetic field (IMF) that was predominantly northward but had several southward turnings. We have inferred the sources of the ions in this distribution function by following approximately 90,000 ion trajectories backward in time using time-dependent electric and magnetic fields obtained from a global MHD (magnetohydrodynamic) simulation. Wind data were used as input for the MHD model. We found that three sources contributed to this distribution: the ionosphere, the plasma mantle which had near-Earth and distant tail components, and the low latitude boundary layer (LLBL). Moreover, distinct structures in the low energy part of the distribution function were found to be associated with individual sources. Structures near 0 deg pitch angle were made up of either ionospheric or plasma mantle ions, while structures near 90 deg pitch angle were dominated by ions from the LLBL source. Particles that underwent nonadiabatic acceleration were numerous in the higher energy part of the ion distribution function, whereas ionospheric and LLBL ions were mostly adiabatic. A large proportion of the near-Earth mantle ions underwent adiabatic acceleration, while most of the distant mantle ions experienced nonadiabatic acceleration.

Ashour-Abdalla, M.↗
NASA NTRS2011

Global Magnetospheric Response to an Interplanetary Shock: THEMIS Observations

We investigate the global response of geospace plasma environment to an interplanetary shock at approx. 0224 UT on May 28, 2008 from multiple THEMIS spacecraft observations in the magnetosheath (THEMIS B and C) and the mid-afternoon (THEMIS A) and dusk magnetosphere (THEMIS D and E). The interaction of the transmitted interplanetary shock with the magnetosphere has global effects. Consequently, it can affect geospace plasma significantly. After interacting with the bow shock, the interplanetary shock transmitted a fast shock and a discontinuity which propagated through the magnetosheath toward the Earth at speeds of 300 km/s and 137 km/s respectively. THEMIS A observations indicate that the plasmaspheric plume changed significantly by the interplanetary shock impact. The plasmaspheric plume density increased rapidly from 10 to 100/ cubic cm in 4 min and the ion distribution changed from isotropic to strongly anisotropic distribution. Electromagnetic ion cyclotron (EMIC) waves observed by THEMIS A are most likely excited by the anisotropic ion distributions caused by the interplanetary shock impact. To our best knowledge, this is the first direct observation of the plasmaspheric plume response to an interplanetary shock's impact. THEMIS A, but not D or E, observed a plasmaspheric plume in the dayside magnetosphere. Multiple spacecraft observations indicate that the dawn-side edge of the plasmaspheric plume was located between THEMIS A and D (or E).

Zhang, Hui↗