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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 19 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1994

A survey of bidirectional greater than or equal to MeV ion flows during the Helios 1 and Helios 2 mission: Observations from the Goddard Space Flight Center instruments

A survey is made of 1.1-2.1 MeV and 3-21 MeV bidirectional ion flows (BIFs) in the solar wind at 0.3-1.0 AU observed by the Goddard Space Flight Center instruments on the Helios 1 and Helios 2 spacecraft during the spacecraft mission in 1974-1984 and 1979-1980, respectively. Some 774 events have been identified Helios 1, and 223 at Helios 2, with mean durations of approximately 2.5 hr at each spacecraft. BIFs were observed for approximately 1%-3% of the observation time during solar minimum conditions in 1975-1977 and for approximately 10%-14% in 1980-1981 around solar maximum. These occurrence rates are similar to those of approximately 1 MeV BIFs observed at the Interplanetary Monitoring Platform 8 and International Sun Earth Explorers (ISEE) 3 spacecraft, and of bidirectional electron heat fluxes at ISEE 3. Solar wind plasma parameters during BIFs were similar to those found generally during the Helios missions, though BIFs have a greater tendency to be associated with cool, low-beta plasma, moderately enhanced and low-variance magnetic fields, both less than 300 km/s and greater than 750 km/s solar wind. Solar wind features associated with the greater than 4 hr duration BIFs include clear plasma shock-driver signatures: approximately 36% of the events; postshock plasma, not associated with shock-driver signatures: approximately 13%; noncompressive density enhancements: approximately 22% (half associated with plasma proton temperature depression); high-speed streams not associated with shocks: approximately 10%; corotating interaction regions: approximately 5%; immediately upstream of shocks: approximately 5%. Around 8% were associated with other solar wind structures, while approximately 4% showed no associated structure. BIFs were present in several of the shock drivers associated with coronal mass ejections (CMEs) observed by the Solwind coronagraph during intervals when Helios 1 was off the limbs of the Sun, showing directly the association of some BIFs with CMEs. some BIFs with CMEs.

Richardson, I. G.↗
NASA NTRS1987

Origin and evolution of fluctuations in the solar wind - Helios observations and Helios-Voyager comparisons

Hour-averaged data from the Helios and Voyager spacecraft are used here to investigate the origin and evolution of low-frequency interplanetary fluctuations from 0.3 to 20 AU. The previously observed evolution toward a less purely Alfvenic state with increasing heliocentric distance is shown to occur more rapidly in the inner heliosphere and in low-speed as well as high-speed streams. It is concluded that outward-traveling flucutations are predominantly generated by the sun, but that in situ turbulence, most likely due to stream shear, generates fluctuations with both inward and outward senses of correlation.

Roberts, D. A.↗
NASA NTRS1991

Bidirectional MeV/n ion intervals - Observations from the Goddard Space Flight Center instruments on the ISEE 3/ICE, IMP 8, Helios 1 and Helios 2 spacecraft

A search is made for intervals of bidirectional energetic ion streaming in approximately 1 MeV data from the instruments on ISEE 3/ICE, IMP 8 and Helios 1 and 2 during 1973 to 1989. The longest duration intervals are found around solar maximum, consistent with the expected association with coronal mass ejections. The ISEE 3/ICE intervals are associated with previously identified bidirectional 35-1000 keV ions and solar-wind electron heat fluxes, though additional bidirectional intervals are found.

Richardson, I. G.↗
NASA NTRS1970

HELIOS Third Joint Working Group Meeting

During the past six months since the Second Helios Joint Working Group Meeting held 27-30 April 1970 at Goddard Space Flight Center, the TDS Sub-Group supported the Helios Project Office and the other Sub-Groups in the timely disposition of action items and the dissemination of information pertinent to the development of interface documentation. Of particular importance during this time period was the Project's decision to incorporate a single-channel telemetry system design aboard the spacecraft. The TDS Sub-Group participated actively in the process that led to this decision. Still under active study with TDS participation is the pending Project Office decision regarding the incorporation of a ranging capability within the telecommunications design. The TDS Sub-Group assisted the Mission Analysis and Operations Sub-Group in establishment of a study effort concerning the Near-Earth Sequence of Events from launch to launch plus 8 hours. This study, which will provide valuable data for the spacecraft telecommunications design, will include participation by the Experiment, Launch Vehicle, Spacecraft, as well as the TDS and MA&O Sub-Groups. Also during the past 6-month period, the TDS, in conjunction with the Spacecraft Sub-Group, initiated activity to develop the Helios Spacecraft/TDS Compatibility Test Plans and Procedures. Activity concerning the foregoing interface discussions has been and will continue to be based upon the "TDS Estimated Capabilities Document for the Helios Missions" (613-1), and the "DSN/Flight Project Interface Design Handbook" (810-5). These will continue to be considered TDS controlling documents until specific Helios Project/TDS interface documentation is generated and signed off by the respective parties. In addition to the above, the DSN continued the Helios Trainee Program with seven GfW/DFVLR trainees in residence at JPL. Two trainees will complete their year's residency concurrent with the Third Helios Joint Working Group Meeting, while four new trainees are expected to arrive following the Third Helios Joint Working Group Meeting. These and other activities are reported in detail in the paragraphs that follow.

Ousley, Gilbert↗
NASA NTRS1976

Helios mission support

With Helios-1 completing its third perihelion and Helios-2 passing its first perihelion, much valuable scientific data were obtained about the inter-earth-sun regions. The first solar occultation of Helios-2 is anxiously awaited as the next important mission phase. Preparations are underway for Helios-2 first entry into solar occultation in mid-May 1976. This article reports on the activities around Helios-1 and -2 perihelions.

Goodwin, P. S.↗
NASA NTRS1976

The Helios program and the sun

Helios A and B are the first two missions inside the orbit of the Mercury towards the sun. They were launched from Cape Kennedy December 10, 1974 and January 15, 1976 respectively. The interplanetary cruise in the ecliptic plane carried the Helios Solar Probes in an ecliptical orbit around the sun to perihelions as close as 0.31 (Helios A) and 0.29 (Helios B) Astronomical Units to the sun. In this technical paper the scientific mission and German and American plans and design versus accomplished mission are presented by the German and United States Project Managers and the Mission Operations Manager. A brief outline of the scope of the project, spacecraft and experiments development, integration and test programs is given. Engineering and system performance results from the Helios A and B flights, which succeeded in passing closer to the sun than any previous spacecraft, are presented. Some of the preliminary scientific findings of the ten active and two passive experiments of this ambitious German/United States cooperative project are outlined.

Ousley, G. W.↗
NASA NTRS1995

CME masses measured by the HELIOS spacecraft photometers

We have cataloged 160 CMEs detected in the HELIOS 1 and 2 90 deg zodiacal light photometers observed from 1975-1985. The HELIOS 1 and 2 spacecraft orbited from 0.3 to 1.0 AU on 6-month orbits. From the photometer observations of Thomson-scattered light in the inner heliosphere, we have determined CME masses for these events using two methods: (1) by integration over the contours drawn between the three photometers at a given time; and (2) by integration of the mass flow over time past a given photometer. The second method, not readily available using coronagraph observations, is derived from CME speeds measured by using the timing of the peak CME brightness from the 16 deg to 31 deg sets of photometers. The two different HELIOS methods of determining CME mass are consistent with one another for individual CMEs. We find that the CME mass values range from 10(exp 15)g to nearly 10(exp 17)g. We compare the mass distributions of HELIOS-measured CMEs with those from coronagraphs and find that CMEs measured by HELIOS over the same time interval are generally more massive. The solar cycle variation of the total CME mass present in the heliosphere varies by over a factor of approximately 15 from solar minimum to solar maximum. Slightly more massive CMEs carry the bulk of the CME mass during maximum. The total CME mass at solar maximum is found to be near 15% of the total solar wind mass.

Jackson, B. V.↗
NASA NTRS1988

Data reduction and analysis of HELIOS plasma wave data

Reduction of data acquired from the HELIOS Solar Wind Plasma Wave Experiments on HELIOS 1 and 2 was continued. Production of 24 hour survey plots of the HELIOS 1 plasma wave data were continued and microfilm copies were submitted to the National Space Science Data Center. Much of the effort involved the shock memory from both HELIOS 1 and 2. This data had to be deconvoluted and time ordered before it could be displayed and plotted in an organized form. The UNIVAX 418-III computer was replaced by a DEC VAX 11/780 computer. In order to continue the reduction and analysis of the data set, all data reduction and analysis computer programs had to be rewritten.

Anderson, Roger R.↗
NASA NTRS1992

Coronal Alfven waves detected by radio sounding during the solar occultations of the Helios spacecraft

The two Helios spacecraft underwent regular solar occultations during their extended missions from Dec 1974-Feb 1986 (Helios 1) and Jan 1976-Mar 1980 (Helios 2) thereby providing many opportunities for radio propagation experiments in the solar corona. On certain rare occasions over the course of these investigations, Faraday rotation measurements of the linearly polarized Helios signals could be recorded simultaneously at two widely-spaced ground stations. Many of these two-station measurement intervals display clear evidence of wave-like structures with quasi-periods of the order of a few minutes to a few hours. These structures are attributed to coronal Alfven waves. The radial propagation direction and velocity of these waves are estimated from a cross-correlation analysis of the data between the two stations. The majority of the waves appear to propagate away from the Sun, but about 30 percent of the cases indicate a propagation direction toward the Sun.

Bird, M. K.↗
NASA NTRS1992

Characteristics of CMEs observed in the heliosphere using Helios photometer data

The zodiacal light photometers on the two Helios spacecraft have been used to detect and study mass ejections and other phenomena emanating from the sun and traversing the heliosphere within 1 AU. We have recently compiled a complete list of all of the significant white light transient events detected from the 90-deg photometers on both Helios spacecraft. This is a preliminary report on the long-term frequency of occurrence of these events; it emphasizes newly processed data from Helios-l from 1975 through 1982 and viewed south of the ecliptic. With the large Helios photometer data base, we will be able to identify the fraction of the 90 deg events which are heliospheric CMEs and determine their characteristics.

Webb, D. F.↗
NASA NTRS1975

HELIOS dual swept frequency radiometer

The HELIOS dual swept frequency radiometer, used in conjunction with a dipole antenna, was designed to measure electromagnetic radiation in space. An engineering prototype was fabricated and tested on the HELIOS spacecraft. Two prototypes and two flight units were fabricated and three of the four units were integrated into the HELIOS spacecraft. Two sets of ground support equipment were provided for checkout of the radiometer.

White, J. R.↗
NASA NTRS1976

Titan/Centaur D-1TTC-5 Helios B flight data report

The fourth operational flight of the newest NASA unmanned launch vehicle is reported. The spacecraft was the Helios B, the second of two solar probes designed and built by the Federal Republic of Germany. The primary mission objective, to place the Helios spacecraft on a heliocentric orbit in the ecliptic plane with a perihelion distance of 0.29 AU, was successfully accomplished. After successful injection of the Helios spacecraft, a series of experiments were performed with the Centaur stage to demonstrate its operational capabilities. All objectives of the extended mission phase were successfully met. This report presents the analysis of the launch vehicle flight data for the primary mission phase of the TC-5 flight.

Adams, K. A.↗
NASA NTRS1976

Tracking and data systems support for the Helios project. Volume 1: Project development through end of mission, phase 2

The overall evolution of the Helios Project is summarized from its conception through to the completion of the Helios-1 mission phase 2. Beginning with the project objectives and concluding with the Helios-1 spacecraft entering its first superior conjunction (end of mission phase 2), descriptions of the project, the mission and its phases, international management and interfaces, and Deep Space Network-spacecraft engineering development in telemetry, tracking, and command systems to ensure compatibility between the U.S. Deep Space Network and the German-built spacecraft are included.

Goodwin, P. S.↗
NASA NTRS1976

Helios mission support

Deep Space Network support of the Helios mission is reported. Downlink signal degradation on the Helios-1 spacecraft and occultation of Helios-2 are discussed. Capability and performance of the network are assessed.

Goodwin, P. S.↗