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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 595 records · Page 33
All sourcesNASA NTRSDOE OSTI
NASA NTRS1988

Advanced Receiver tracking of Voyager 2 near solar conjunction

The Advanced Receiver (ARX) was used to track the Voyager 2 spacecraft at low Sun-Earth-Probe (SEP) angles near solar conjunction in December of 1987. The received carrier signal exhibited strong fluctuations in both phase and amplitude. The ARX used spectral estimation and mathematical modeling of the phase and receiver noise processes to set an optimum carrier tracking bandwidth. This minimized the mean square phase error in tracking carrier phase and thus minimized the loss in the telemetry signal-to-noise ratio due to the carrier loop. Recovered symbol SNRs and errors in decoded engineering data for the ARX are compared with those for the current Block 3 telemetry stream. Optimum bandwidths are plotted against SEP angle. Measurements of the power spectral density of the solar phase and amplitude fluctuations are also given.

Brown, D. H.↗
NASA NTRS1986

Management experience of an international venture in space The Ulysses mission

The management of the Ulysses project, a probe which will fly a solar polar orbit, is described. The 5-yr mission will feature a flyby of Jupiter to deflect the spacecraft into a high-inclination orbit. Data on the solar corona, solar wind, the sun-wind interface, the heliospheric magnetic field, solar and nonsolar cosmic rays, etc., will be gathered as a function of the solar latitude. NASA will track and control the probe with the Deep Space Network. JPL provides project management for NASA while the Directorate of Scientific Programs performs ESA management functions. The DOE will provide a radioisotope thermoelectric generator while NASA and ESA each supply half the scientific payload. A NASA-ESA Joint Working Group meets about twice per year to monitor the project and discuss the technical and scientific requirements. Safety issues and measures which are being addressed due to the presence of the Pu-238 heat source for the RTG are discussed.

Yoshida, Ronald Y.↗
NASA NTRS2002

The Interstellar Probe (ISP): Pre-Perihelion Trajectories and Application of Holography

Between February and September 2001, a number of aspects of the solar-sail-launched Interstellar probe (ISP), which is under consideration by NASA for launch in the 2010-2015 timeframe, were researched. The effort was conducted in New York City (NYC) February-May, at Marshall Space Flight Center (MSFC) May-July (when the PI served as a NASA Summer 2001 Faculty Fellow), and in NYC August-September. In addition to the people listed on the title sheet, many people in NYC and at MSFC participated in this research.

Matloff, G. L.↗
NASA NTRS2002

The Interstellar Probe (ISP): Pre-Perihelion Trajectories and Application of Holography

Between February and September 2001, a number of aspects of the solar-sail-launched Interstellar probe (ISP), which is under consideration by NASA for launch in the 2010-2015 timeframe, were researched. The effort was conducted in New York City (NYC) February-May, at Marshall Space Flight Center (MSFC) May-July (when the PI served as a NASA Summer 2001 Faculty Fellow), and in NYC August-September. In addition to the people listed on the title sheet, many people in NYC and at MSFC participated in this research.

Matloff, G. L.↗
NASA NTRSDate not supplied

Researching the Planetary Environment with an Interstellar Probe

In 2018, a study originated with the idea of a mission that would be feasible to launch in the 2030s, targeting 1000 AU within 50 years using current technology. While the primary objective of such an Interstellar Probe would be to understand the heliosphere and interstellar medium, this probe offers an excellent opportunity for rock, dust, and ice sciences. In the initial stages of its journey through the solar system, this Interstellar Probe would carry out a wide range of potential observations to study the planetary environment, particularly focusing on dust/ice analysis and planetary science through fly-bys of critical science targets, especially in the trans-Neptunian region. A flyby of a trans-Neptunian dwarf planet, such as Quaoar, would provide further geological, compositional, and geophysical context for Earth-based observations. Aside from in-situ remote sensing techniques, VISIR and dust analyses would also benefit in this region of the solar system to determine (i) dominant ice and dust compositions and potential variations depending on heliocentric distance (e.g., chemical or irradiated products); (ii) collections and identification of PAH-type components; and (iii) solar nebula chemical and mechanical processing, such as collisions. The purpose of our poster is to provide a background of the Interstellar Probe’s objectives and possible instrumentation to offer insight on current questions about the planetary environment.

C J Ahrens↗
NASA NTRS1995

Exploring small bodies in the outer solar system with stellar occultations

Stellar occultation observations probe the atmospheric structure and extinction of outer solar system bodies with a spatial resolution of a few kilometers, and an airborne platform allows the observation of occultations by small bodies that are not visible from fixed telescopes. Results from occultations by Triton, Pluto, and Chiron observed with KAO are discussed, and future directions for this program are presented.

Elliot, Jim L.↗
NASA NTRS1981

Empirical model of the interaction of the solar wind with the daytime ionosphere of Venus

Interplanetary probe data on the interaction of the solar wind with the ionosphere of Venus are examined. It is shown that the ionospheric pressure above the ionopause is approximately equal to the dynamic pressure of the solar wind, while the value of magnetic pressure at the ionopause amounts to about 2/3 of the value of external and ionospheric pressures. A first-approximation model is proposed for changes of pressure at the ionopause as a function of height and solar zenith angle. This model makes it possible to determine the 'instantaneous' profile of the ionopause for a given solar-wind pressure.

Vaisberg, O. L.↗
NASA NTRS1991

The quasi-stationary and transient states of the solar wind

While the last 30 years' probing of the transient and quasi-stationary states of the solar wind by interplanetary spacecraft have yielded a clear differentiation of the physical properties of the two types of wind, the processes involved in their acceleration remains unclear; neither is the coronal heating mechanism implicated in the solar wind's existence entirely clear. Attention is presently given to recent evidence for a connection between heating and acceleration mechanisms. The transient wind undergoes greater expansion between the sun and 1 AU than the quasi-stationary wind. The quasi-stationary wind is driven by energy and momentum that arise from solar convection and are carried throughout a region that extends from the base of the corona to beyond the critical point at which the flow becomes supersonic.

Neugebauer, M.↗
NASA NTRS1990

Global models of Ne and Te at solar maximum based on DE-2 measurements

Newly developed global models of the electron density of (Ne) and (Te) in the F-region at solar maximum, based on Langmuir probe measurements from the Dynamics Explorer-2 satellite, are compared with solar minimum models that were developed earlier from Atmosphere Explorer data. Spherical harmonics are used in both models to describe the variations with geomagnetic latitude and local time, but the solar maximum model also includes longitudinal variations. The solar minimum models were for the fixed altitudes of 300 km and 400 km, while the solar maximum model covers all altitudes between 300 and 1000 km. In this paper, the global patterns of Ne and Te at 400 km at solar maximum and minimum are compared with the IRI model for the corresponding parts of the solar cycle. In most respects, the IRI model describes the empirical models quite well at both solar maximum and solar minimum.

Brace, L. H.↗
NASA NTRS2013

X-Ray Diffractive Optics

X-ray optics were fabricated with the capability of imaging solar x-ray sources with better than 0.1 arcsecond angular resolution, over an order of magnitude finer than is currently possible. Such images would provide a new window into the little-understood energy release and particle acceleration regions in solar flares. They constitute one of the most promising ways to probe these regions in the solar atmosphere with the sensitivity and angular resolution needed to better understand the physical processes involved. A circular slit structure with widths as fine as 0.85 micron etched in a silicon wafer 8 microns thick forms a phase zone plate version of a Fresnel lens capable of focusing approx. =.6 keV x-rays. The focal length of the 3-cm diameter lenses is 100 microns, and the angular resolution capability is better than 0.1 arcsecond. Such phase zone plates were fabricated in Goddard fs Detector Development Lab. (DDL) and tested at the Goddard 600-microns x-ray test facility. The test data verified that the desired angular resolution and throughput efficiency were achieved.

Dennis, Brian↗
NASA NTRS1974

A tracking polarimeter for measuring solar and ionospheric Faraday rotation of signals from deep space probes

A tracking polarimeter implemented on the 64-m NASA/JPL paraboloid antenna at Goldstone, Calif., is described. Its performance is analyzed and compared with measurements. The system was developed to measure Faraday rotation in the solar corona of the telemetry carrier from the Pioneer VI spacecraft as it was occulted by the sun. It also measures rotation in the earth's ionosphere and is an accurate method of determining spacecraft orientation. The new feature of this system is its use of a pair of quarter-wave plates to allow the synthesis of a rotating feed system, while requiring the rotation of only a single section of waveguide. Since the polarization sensing is done at RF and the receiver operates essentially as a null detector, the system's accuracy is superior to other polarization tracking schemes. In addition, the antenna size and maser preamplifier provide unsurpassed sensitivity. The associated instrumentation used in the Pioneer VI experiment is also described.

Ohlson, J. E.↗
NASA NTRS2007

Solar Modulation of Low-Energy Antiproton and Proton Spectra Measured by BESS

The spectra of low-energy cosmic-ray protons and antiprotons have been measured by BESS in nine high-latitude balloon flights between 1993 and 2004. These measurements span a range of solar activity from the previous solar minimum through solar ma>:im%am and the onset of the present solar minimum, as well as a solar magnetic field reversal from positive to negative in 2000. Because protons and antiprotons differ only in charge sign, these simultaneous measurements provide a sensitive probe of charge dependent solar modulation. The antiproton to proton ratio measured by BESS is consistent with simple spherically symmetric models of solar modulation during the Sun's positive polarity phase, but favor charge-sign-dependent drift models during the negative phase. The BESS measurements will be presented and compared to various models of solar modulation.

Mitchell, John W.↗
NASA NTRS2006

The Solar System: Recent Exploration Results

The solar system has been visited by space probes, ranging from the Mariner Mercury-Venus mission exploring inward toward the sun, and continuing through the Voyager probes out into interstellar space and (on its way now) the New Horizons probe to Pluto and the Kuiper belt. This talk examines what we know of the planets of the solar system from probes, and talks about where we will go from here.

Landis, Geoffrey A.↗
NASA NTRS1988

Solar EUV measurements at Venus based on photoelectron emission from the Pioneer Venus Langmuir probe

Data from the Pioneer Venus Langmuir probe, collected since 1979 (and thus, including the period between solar maximum in 1979-1980 and solar minimum in 1986-1987) are examined. Calculations show that about 51 percent of the solar emission at Venus is due to Lyman alpha (1216 A), 46 percent is produced by wavelengths between 550 and 1100 A, and less than 3 percent is due to wavelengths longer than Lyman alpha. The photocurrents were found to exhibit variations related to the solar cycle and solar rotation, as well as a major 7.2-month periodicity. Three different indices of solar EUV behavior at Venus were derived, which include the photoemission current itself, the total EUV flux, and an F(10.7)-like solar index, and are compared with related measurements made simultaneously at earth.

Brace, L. H.↗