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At least 721 records · Page 40

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NASA NTRS1962

United States Space Explorations 1958

The film describes preparation and launch of five satellites and two space probes during 1958. On January 31, a Jupiter vehicle launched Explorer I into space. Data from this satellite was used to identify the van Allen radiation belts. On March 17, a Vanguard I rocket launched an Earth satellite with solar batteries. Data from the mission was used to determine that the Earth is slightly pear-shaped. On March 26, Explorer III was launched to further study the van Allen belts, micrometeoroid impacts, and internal and external temperatures. Explorer IV, launched on July 26, was intended to study radiation and temperature data. A lunar probe, ABLE I, was intended to measure radiation, magnetic fields of Earth and the Moon, density of micrometeoric matter, and internal temperatures. A four-stage rocket was used in the launch. However, a turbo-pump failed and the liquid oxygen pump stopped, resulting in a failed mission. On October 10, Pioneer I was launched by an ABLE vehicle. First and second stage velocity was less than desired and the probe did not leave Earth orbit. Attempts to attain escape velocity were unsuccessful. On December, a Jupiter boost vehicle was used to launch Juno II, with Pioneer III as the payload. Escape velocity was reached and Pioneer III left Earth's atmosphere. Failed launches, such as those of Vanguard boost vehicles and several Explorer satellites, also added to scientific knowledge.

Source record↗

DOE OSTI2025

A Multivariate Space‐Time Dynamic Model for Characterizing the Atmospheric Impacts Following the Mt. Pinatubo Eruption

The June 1991 Mt. Pinatubo eruption resulted in a massive increase of sulfate aerosols in the atmosphere, absorbing radiation and leading to global changes in surface and stratospheric temperatures. A volcanic eruption of this magnitude serves as a natural analog for stratospheric aerosol injection, a proposed solar radiation modification method to combat a warming climate. The impacts of such an event are multifaceted and region-specific. Our goal is to characterize the multivariate and dynamic nature of the atmospheric impacts following the Mt. Pinatubo eruption. We developed a multivariate space-time dynamic linear model to understand the full extent of the spatially- and temporally-varying impacts. Specifically, spatial variation is modeled using a flexible set of basis functions for which the basis coefficients are allowed to vary in time through a vector autoregressive (VAR) structure. This novel model is cast in a Dynamic Linear Model (DLM) framework and estimated via a customized MCMC approach. We demonstrate how the model quantifies the relationships between key atmospheric parameters prior to and following the Mt. Pinatubo eruption with reanalysis data from MERRA-2 and highlight when such a model is advantageous over univariate models.

Dynamic Linear Model↗

NASA NTRS1980

Sun Series program for the REEDA System

Modifications made to data bases and to four programs in a series of computer programs (Sun Series) which run on the REEDA HP minicomputer system to aid NASA's solar activity predictions used in orbital life time predictions are described. These programs utilize various mathematical smoothing technique and perform statistical and graphical analysis of various solar activity data bases residing on the REEDA System.

Shankle, R. W.↗

NASA NTRS1986

The need for isotopic data on refractory elements in the solar wind

The Sun accounts for the bulk of material in the solar system. Information on the isotopic composition of elements in the solar wind is therefore essential for an understanding of the contribution made by each nucleogenetic component that has been identified in meteorites. Recent work suggests that isotopic data on the solar wind may also help us to understand the physical process that is concentrating light elements at the solar surface. Refractory and volatile elements would behave alike under the conditions of solar fractionation. Prolonged exposure of foils at 1AU from the sun would be a relatively inexpensively way to collect the quantity of solar wind implanted refractory elements needed to test this hypothesis.

Manuel, O. K.↗

NASA NTRS1989

Atmospheric drag model calibrations for spacecraft lifetime prediction

Although solar activity prediction uncertainty normally dominates decay prediction error budget for near-Earth spacecraft, the effect of drag force modeling errors for given levels of solar activity needs to be considered. Two atmospheric density models, the modified Harris-Priester model and the Jacchia-Roberts model, to reproduce the decay histories of the Solar Mesosphere Explorer (SME) and Solar Maximum Mission (SMM) spacecraft in the 490- to 540-kilometer altitude range were analyzed. Historical solar activity data were used in the input to the density computations. For each spacecraft and atmospheric model, a drag scaling adjustment factor was determined for a high-solar-activity year, such that the observed annual decay in the mean semimajor axis was reproduced by an averaged variation-of-parameters (VOP) orbit propagation. The SME (SMM) calibration was performed using calendar year 1983 (1982). The resulting calibration factors differ by 20 to 40 percent from the predictions of the prelaunch ballistic coefficients. The orbit propagations for each spacecraft were extended to the middle of 1988 using the calibrated drag models. For the Jaccia-Roberts density model, the observed decay in the mean semimajor axis of SME (SMM) over the 4.5-year (5.5-year) predictive period was reproduced to within 1.5 (4.4) percent. The corresponding figure for the Harris-Priester model was 8.6 (20.6) percent. Detailed results and conclusions regarding the importance of accurate drag force modeling for lifetime predictions are presented.

Binebrink, A. L.↗

NASA NTRS1990

Upstream pressure variations associated with the bow shock and their effects on the magnetosphere

The AMPTE IRM solar wind data are analyzed to determine the relationship between upstream pressure fluctuations and magnetospheric perturbations. It is argued that the upstream pressure variations are not inherent in the solar wind but rather are associated with the bow shock. This conclusion follows from the fact that the upstream field strength and density associated with perturbations are highly correlated with each other, while they tend to be anticorrelated in the undisturbed solar wind, and that the upstream perturbations occur within the foreshock or at its boundary. The results imply a mode of interaction between the solar wind upstream and the magnetosphere whereby density changes produced in the foreshock subsequently convect through the bow shock and impinge on the magnetosphere. Upstream pressure perturbations should create significant effects on the magnetopause and at the foot of nearby field lines that lead to the polar cusp ionosphere.

Fairfield, D. H.↗

NASA NTRS1986

Initial results of the Global Thermospheric Mapping Study (GTMS)

The Global Thermospheric Mapping Study (GTMS) is a multi-technique experimental study of the thermosphere designed to map simultaneously its spatial and temporal morphology with a thoroughness and diversity of measurement techniques heretofore unachieved. The GTMS is designed around the Incoherent Scatter Radar Chain in the western hemisphere. The European incoherent scatter radars and the worldwide communities of Fabry-Perot interferometers, meteor wind radars, partial reflection drifts radars, MST radars, and satellite probes are included to extend the spatial coverage and types of measurements available. Theoretical and modeling support in the areas of thermospheric and ionospheric structure, tides, and electric fields are included to aid in program planning and data interpretation. Solar activity was low on the three observation days (F10.7 = 97, 98, 96) and magnetic conditions were unsettled to active (A = 10, 12, 20). All six incoherent scatter radar facilities collected data. Each collected F region data day and night while Saint Santin and Millstone Hill additionally collected E region data during daylight hours. Initial results from Sondrestrom and Millstone Hill are presented. Good quality Fabry Perot data were collected at Fritz Peak and San Jose dos Campos. Weather conditions produced poor results at Arequipa and Arecibo. Initial results from Fritz Peak are presented. Mesosphere/lower-thermosphere observations were conducted under the ATMAP organization. The magnetometer chains also were operational during this campaign. Initial thermospheric general circulation model predictions were made for assumed solar-geophysical conditions, and selected results are presented.

Oliver, W. L.↗

NASA NTRS1993

Composite Mg II solar activity index for solar cycles 21 and 22

On the basis of version 1.0 of the composite MG II solar activity index data set, it is shown that the change in the 27-day running average of the Mg II index from solar maximum to solar minimum is about 8 percent for solar cycle 21 and about 9 percent for solar cycle 22 through January 1992. Scaling factors based on the short-term variations in the Mg II index and solar irradiance data sets are developed for each instrument to estimate solar variability at mid-UV and near-UV wavelengths. A set of composite scale factors are derived for use with the present composite MG index. Near 205 cm, where solar irradiance variations are important for stratospheric chemistry, the estimated change in irradiance during solar cycle 22 is about 10 +/- 1 percent using the composite Mg II index (version 1.0) and scale factors.

Deland, Matthew T.↗

NASA NTRS1982

Characteristics of shocks in the solar corona, as inferred from radio, optical, and theoretical investigations

Solar radio bursts of spectral type II provide one of the chief diagnostics for the propagation of shocks through the solar corona. Radio data on the shocks are compared with computer models for propagation of fast-mode MHD shocks through the solar corona. Data on coronal shocks and high-velocity ejecta from solar flares are then discussed in terms of a general model consisting of three main velocity regimes.

Maxwell, A.↗

NASA NTRS1994

Flow properties of the solar wind obtained from white light data and a two-fluid model

The flow properties of the solar wind from 1 R(sub s) to 1 AU were obtained using a two fluid model constrained by density and scale height temperatures derived from white light observations, as well as knowledge of the electron temperature in coronal holes. The observations were obtained with the white light coronographs on SPARTAN 201-1 and at Mauna Loa (Hawaii), in a north polar coronal hole from 1.16 to 5.5 R(sub s) on 11 Apr. 1993. By specifying the density, temperature, Alfven wave velocity amplitude and heating function at the coronal base, it was found that the model parameters fit well the constraints of the empirical density profiles and temperatures. The optimal range of the input parameters was found to yield a higher proton temperature than electron temperature in the inner corona. The results indicate that no preferential heating of the protons at larger distances is needed to produce higher proton than electron temperatures at 1 AU, as observed in the high speed solar wind.

Habbal, Shadia Rifai↗

NASA NTRS1995

Solar wind helium observations on the Prognoz 7 satellite

Solar wind data obtained with ion mass-energy-spectrometer on the Prognoz 7 satellite are analyzed to study the alpha-particle and proton features in different types of solar wind streams. In the streams from coronal holes the abundance of helium relative to proton slightly increases with increasing solar wind flux and proton density while in the streams from coronal streamers it decreases. These results indicate that the mechanisms of solar wind formation in different regions of solar corona differ. Preferential alpha-particle acceleration and heating are often observed in the streams from coronal holes. Minimum (as well as negative) values of alpha-proton velocity difference are recorded in the heliospheric current sheet, shocked plasma, and coronal mass ejections. Dependences of alpha-proton velocity difference and temperature ratio on several MHD parameters (Alfven velocity, number of Coulomb collisions. etc.) are compared for different types of streams. For velocity difference the dependences in streams from coronal holes and streamers are often similar to each other, and they differ from the ones in the heliospheric current sheet. For temperature ratio the dependences in heliospheric current sheet and streams from coronal streamers are similar, and they differ in streams from coronal holes.

Yermolaev, Yu. I.↗

DOE OSTI2023

NREL Pyrheliometer Comparisons: September 23 - September 28, 2023 (NPC-2023)

Accurate measurements of direct normal (beam) solar irradiance from pyrheliometers are important for developing and deploying solar energy conversion systems, for improving our understanding of Earth's energy budget for climate change studies, and for other science and technology applications involving solar flux. Providing these measurements places many demands on the quality system used by the operator of commercially available radiometers. Maintaining accurate radiometer calibrations that are traceable to an international standard is the first step in producing research-quality solar irradiance measurements. In 1977, the World Meteorological Organization (WMO) established the World Radiometric Reference (WRR) as the international standard for the measurement of direct normal solar irradiance (Frohlich 1991). The WRR is an internationally recognized, detector-based measurement standard determined by the collective performance of six electrically self-calibrated absolute cavity radiometers comprising the World Standard Group (WSG). Various countries, including the United States, have contributed these specialized radiometers to the Physikalisch-Meteorologisches Observatorium Davos - World Radiation Center (PMOD/WRC) to establish the WSG. As with all measurement systems, Absolute Cavity Radiometers (ACR) are subject to performance changes over time. Therefore, PMOD/WRC in Davos, Switzerland, hosts an quinquennial International Pyrheliometer Comparison (IPC) event for transferring the WRR to participating radiometers by invitation. The National Renewable Energy Laboratory (NREL) has represented the U.S. Department of Energy (DOE) in each IPC since 1980. And NREL has developed and maintained a select group of absolute cavity radiometers with direct calibration traceability to the WRR, and it uses these reference instruments to calibrate pyrheliometers and pyranometers using the International Organization for Standardization (ISO) 17025-accredited Broadband Outdoor Radiometer Calibration (BORCAL) process (Reda et al. 2008). To fill the gap between each IPC, NREL pyrheliometer comparisons (NPCs) are held annually at the Solar Radiation Research Laboratory (SRRL) in Golden, Colorado. Open to all ACR owners and operators, each NPC provides an opportunity to determine the unique WRR transfer factor (WRR-TF) for each participating pyrheliometer. By adjusting all subsequent pyrheliometer measurements by the appropriate WRR-TF, the solar irradiance data are traceable to the WRR.

14 SOLAR ENERGY↗

NASA NTRS1977

Verification test of the MSFC solar simulator using a Honeywell double-covered liquid solar collector

Additional verification data to support the utilization of the MSFC Solar Simulator for testing solar collectors was obtained. The Honeywell double-covered liquid solar collector number 2 for which thermal performance data under natural outdoor conditions had been previously obtained was installed on the Solar Simulator and subjected to a series of eight tests under various conditions of wind flow rate. Although these test conditions were not absolutely identical to those of the outdoor tests, they are considered to be sufficiently representative to provide a basis for an accurate comparative analysis of the data recorded for both test programs.

Shih, K., Sr.↗

NASA NTRS1984

Spartan - Space at low-cost

Mission profiles and objectives of the Spartan Shuttle payload are described. Spartan was designed to provide extended observations normally carried out for only a few minutes using sounding rockets. The payload will be placed in co-orbit with the Orbiter by the RMS arm and controlled by a ground-based researcher or by an on-board program. Spartan features minimal battery power, batteries, and control systems and no redundancy. Thermal control is added because the flights last 100-1000 times as long as those on sounding rockets. Data are recorded by an on-board tape recorder and operations are controlled by an on-board microprocessor. Spartan 1 will carry a star-pointer and X-ray detectors for high energy astrophysics experiments. Spartan 2 will gather solar physics data in the form of temperatures of hydrogen gas and ions and electrons. Particle densities will also be monitored and a 43 cm solar telescope will produce UV and white light solar coronagraphs. UV spectroscopy of stars, clouds and galaxies will be performed by the Spartan 3 payload.

Source record↗

NASA NTRS1983

Factors controlling the location of the Venus bow shock

The location of the Venus bow shock determined from magnetic field measurements during the first and third years of Pioneer Venus orbiter operation is examined and compared with nearly simultaneously obtained interplanetary solar wind data to determine those factors that control the size of the Venus bow shock. The location of the intersection of the bow shock with the terminator that is best determined by the data does not vary significantly between years 1979 and 1981 and is only 16 percent more distant than the Venera 9 and 10 shock when account is taken of solar wind aberration. Alfvenic Mach number and magnetosonic Mach number affect the size of the bow shock significantly. Solar wind dynamic pressure has a lesser effect. No significant asymmetries in the shock shape were found either as a result of the orientation of the clock angle of the IMF in the terminator plane or the angle of the IMF relative to the shock normal.

Tatrallyay, M.↗

DOE OSTI2026

Downwelling Shortwave and Longwave Irradiance from CC-RIDER on Mount Soledad

The Clouds and Climate - Remote Integrated Deployment of Radiometers (CC-RIDER) is a suite of five Eppley Laboratory (Inc.) instruments that was deployed during EPCAPE at the secondary Mount Soledad site in La Jolla, CA. A primary and backup Precision Spectral Pyranometer (PSP Primary, PSP Backup) measured broadband downwelling shortwave irradiance in the spectral interval 280-2800 nm. A third Precision Spectral Pyranometer (PSP NIR) was fitted with a near-infrared long pass filter and measured downwelling shortwave irradiance in the spectral interval 780-2800 nm. A Total Ultraviolet Radiometer (TUVR) measured broadband downwelling broadband ultraviolet irradiance in the spectral interval 295-385 nm. A Precision Infrared Radiometer (PIR) Pyrgeometer measured downwelling broadband longwave irradiance in the spectral interval 3.5 - 50 microns. Data collection began on 18 April 2023 at 21:31 UTC and ended on 20 February 2024 at 22:34 UTC. Data were recorded by a Campbell Scientific (Inc.) CR1000X datalogger in one-minute intervals, for a total of 443584 data records. The datalogger was solar powered enabling data collection to proceed without interruption from start to finish.

Clouds and Climate – Remote Integrated DEployement↗

NASA NTRS1981

High latitude stratospheric electrical measurements in fair and foul weather under various solar conditions

Stratospheric electric field and conductivity measurements are presented for sites of latitude greater than 50 deg N GG, during the months of either April or August, in a variety of weather and solar conditions. Vertical electric field data from balloon flights with an average duration of 18 hours at ceiling, in fair weather, are shown to be appropriately modeled by a simple, exponential, altitude-dependent equation. Data collected over electrified clouds and thunderstorms are presented, along with a discussion of the thunderstorm-related electric currents. Current surges in the atmosphere due to DC currents as well as the spheric are calculated, and it is found that in over 1000 hours of balloon data, no direct solar influence is identified except during major flares.

Holzworth, R. H.↗

NASA NTRS1982

Solar rotation measurements at Mount Wilson. III - Meridional flow and limbshift

It is shown that the use of a two-parameter limbshift and a meridional flow velocity fits solar velocity data better than the standard analysis defined by Howard et al. (1980). The data used are the coarse residual velocity arrays, with 34 equal intervals in both sine latitude and sine longitude. There are a total of 2899 full-disk observations between January 1, 1967, and December 12, 1980. The original velocity fields are reconstructed by adding into the residual arrays the large-scale patterns that were measured and removed on a daily basis by a standard reduction. Tests of this reconstituded data set show that no significant errors are introduced in the analysis of large-scale velocity fields. The results of the analysis presented here imply that the study of solar velocity pattern at the level of a few m/s requires that magnetic regions be treated separately from nonmagnetic regions.

Labonte, B. J.↗