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NASA NTRS1982

The International Halley Watch

The International Halley Watch (IHW) is a program designed to promote cooperation, standardization, and archival documentation in all phases of study of Comet Halley during its 1985-86 apparition. Discipline Specialists have been selected to create cooperative nets of ground-based observers encompassing seven different technical areas and to coordinate the observations and publication of results in each. The IHW will promote cooperation among ground-based and space studies of Comet Halley wherever reasonable and feasible. More specifically, the IHW will make ephemerides from the astrometric net available to any country flying a deep space mission. It will coordinate special Halley Watch Days with the arrival dates of space probes or periods of observation from earth orbit. And the IHW will provide a permanent archive in published form of all scientific observations of Comet Halley.

Rahe, J.↗
NASA NTRS1984

Radial gradient of cosmic ray intensity from a comparative study of data from Voyager 1 and 2 and IMP 8

The IMP 8 satellite and Voyager 1 and 2 space probes obtained cosmic ray measurements during the late 1977 to mid-1982 period. Comparisons of 27-day averages of the data show that a positive radial intensity gradient existed on the average during this period, and that the cosmic ray intensity decrease toward solar maximum in 1980-1981 proceeds in a stepwise fashion. The cosmic ray minimum reached in late 1980/early 1981 appears almost simultaneously at 1 AU and at 10 AU, with and without propagation time delay effects, between IMP 8 and the Voyager spacecraft. These data are generally consistent with a heliolatitudinal gradient of 0 + or - 1 percent/deg. Attention is given to the implications of these results in the overall context of cosmic ray modulation theory.

Venkatesan, D.↗
NASA NTRS1984

Evidence for slow-mode shocks in the deep geomagnetic tail

Plasma and field data from the ISEE-3 space probe provide evidence that the lobe-plasma sheet boundary is the central part of the distant geomagnetic tail is often a slow-mode shock. Such shocks are predicted by Petchek's (1964) model of the reconnection. If this model applies, then the ISEE-3 observations place the general location of the reconnection diffusion region closer to the earth than x of about -100 earth radii.

Feldman, W. C.↗
NASA NTRS1984

Launch summary for 1978 - 1982

Data pertinent to the launching of space probes, soundings rockets, and satellites presented in tables include launch date, time, and site; agency rocket identification; sponsoring country or countries; instruments carried for experiments; the peak altitude achieved by the rockets; and the apoapsis and periapsis for satellites. The experimenter or institution involved in the launching is also cited.

Hills, H. K.↗
NASA NTRS1984

Measurements of H2O in Jupiter's Atmosphere from 5 Microns Airborne Observations

Measurement of the abundance and vertical distribution of H2O in Jupiter's atmosphere is discussed. Water was first detected using the Kuiper airborne observatory (KAO) and has also been observed at 5 micrometers by the Voyager infrared spectrometer, IRIS. Studies of H2O in the atmospheres of other planets require special high altitude facilities to reduce the interference of telluric H2O. Jovian H2O absorption lines are overwhelmed by terrestrial H2O at ground-based observatories but they are readily apparent in airborne spectra. Typical column abundances of H2O above ground-based telescopes are about 3000 precipitable micrometers versus only 10 pr micrometers above the KAO at the 12.5 km level. For comparison, there is about 150 pr micrometers H2O above the 3 bar level on Jupiter. Airborne observations also take advantage of cryogenic detectors which have not been used thus far on deep space probes.

Bjoraker, G. L.↗
NASA NTRS1985

Two types of electron events in solar flares

The fluxes and spectra of the flare electrons measured on board Venera-I3 and I4 space probes are compared with the parameters of the hard (E sub x approximately 55 keV) and thermal X-ray bursts. The electron flux amplitude has been found to correlate with flare importance in the thermal X-ray range (r approximately 0.8). The following two types of flare events have been found in the electron component of SCR. The electron flux increase is accompanied by a hard X-ray burst and the electron spectrum index in the approximately 25 to 200 keV energy range is gamma approximately 2 to 3. The electron flux increase is not accompanied by a hard X-ray burst and the electron spectrum is softer (Delta gamma approximately 0.7 to 1.0).

Daibog, E. I.↗
NASA NTRS1985

High-performance double-focusing mass spectrometer

Double focusing was first employed when mass spectrometers of a simpler design were not capable any longer to satisfy increasing demands in mass spectroscopy. One of the successful instruments of the 1930's was the mass spectrometer designed by Mattauch and Herzog (1934). The compactness of the Mattauch-Herzog geometry became particularly important in connection with studies involving the employment of rockets, satellites, or space probes. Another advantage of the considered spectrometer is related to the capability of measuring several masses of ions simultaneously. The instrument design was, therefore adopted for some rocket flights to the upper atmosphere, the investigation of the upper atmosphere of Mars, and for studying the upper atmosphere of Venus. Attention is given to laboratory applications involving the instrument in a somewhat enlarged version, and aspects of instrument operation and performance.

Nier, A. O.↗
NASA NTRS1985

Deep space observations of the east-west asymmetry of solar energetic storm particle events - Voyagers 1 and 2

It has been well established that solar flare shock waves, propagating through the interplanetary medium, accelerate ambient energetic particles, giving rise to the formation of energetic storm particle (ESP) intensity enhancements. However, the acceleration mechanism which is responsible for the generation of ESP events is still under investigation. In the present investigation, energetic proton observations during solar flare ESP events made with the aid of the Voyagers 1 and 2 deep space probes are employed as a basis to examine further the acceleration processes responsible for the generation of ESP events under different 'interplanetary magnetic field-shock front' configurations. It is found that large ESP proton intensity enhancements are superimposed on the ambient solar energetic particle population for solar flare sites to the east of the sun-spacecraft medidian.

Sarris, E. T.↗
NASA NTRS1985

Multispacecraft observations of the east-west asymmetry of solar energetic storm particle events

Energetic proton observations have been obtained by instruments aboard the IMP-7 and -8 spacecraft and Voyager-1 and -2 deep space probes, in order to study the generation of solar flare Energetic Storm Particle Events (ESP) events at widely separated locations on the same shock front which are presumably characterized, on average, by different IMF shock front configurations for solar flare sites. Energetic proton observations indicate that substantial differences in the ESP proton intensity enhancements are detected at these energies for locations on the shock front with wide heliolongitude separations. The present results indicate that acceleration of ESP protons to more than 500 keV takes place at the quasi-perpendicular shock front domain, consistent with the 'shock drift' acceleration mechanism.

Sarris, E. T.↗
NASA NTRS1985

Toward the fully capable AI space mission planner

The necessity of expending numerous ground-side manhours to write extremely concise command codes for deep-space probes in-flight, which carry limited on-board processing capabilities, is encouraging the development of AI modules to perform the same task. An experimental automated sequence planner, Deviser, has proven successful enough, when used on a mainframe computer, to continue with the next generation of the concept, PLAN-IT, an expert scheduler for spacecraft observation targets. The new system will provide the ground-based user with interactive graphic displays for choosing targets and generates an expected time-line. An updated Deviser, using the new modules, will be tested after the Voyager Uranus encounter, and PLAN-IT will be employed to formulate Spacelab activity schedules.

Grenander, S.↗
NASA NTRS1986

Solar dynamic systems for spacecraft power applications

Results are presented of a parametric study of the potential for using solar dynamic (SD) power supply systems on deep space probes. The SD systems would consist of a parabolic concentrator to focus solar energy on a thermal receiver for conversion by Brayton, organic Rankine or Stirling engines. The net thermal power and efficiencies available from each of the types of conversion devices were analyzed for a power requirement of 0.5 kWe. Examinations were also carried out of the optical, thermodynamic, materials and size limitations of the devices. The subsystem drivers were found to be the quality of concentrator reflectance and the system temperature level. Lower temperature systems are preferred for farther distances from the sun, mainly due to the required concentrator area. The SD system could be used out to 6 A.U. in optimal conditions. It is concluded that Brayon and Stirling engines have the best chances for further development, and that Rankine systems have already been optimized. Further evaluations are dependent on the definition of specific mission requirements.

Roschke, E. J.↗
NASA NTRS1986

JHK photometry of candidate stars for occultation by Neptune

Hubbard et al. (1985) have observed the occultation of a star by a ring-like arc of Neptune. The semitransparent, incomplete ring was located at a distance of about 67,000 km from Neptune. In connnection with the program for the Voyager 2 deep space probe to fly past Neptune in 1989 at this distance from the planet, it is urgent to determine the nature of this ring arc or arcs. The best approach to obtain the required information is related to an observation of occultations of stars by Neptune. In this context, a study has been conducted of six stars which will be occulted by Neptune during 1986 and 1987, taking into account their JHK photometry. The obtained data are presented in a table.

Vilas, F.↗
NASA NTRS1986

Pathfinder - Accuracy improvement of comet Halley trajectory for Giotto navigation

The 'Pathfinder' project uses the resources of NASA, ESA and Intercosmos to support the Giotto space probe flyby of comet Halley. The required 500-km approach to comet Halley on the sunward side was so uncertain as to preclude the trajectory's realization with sufficient accuracy on the basis of ground-based astronomical observations alone. Spaceborne observations by the two Vega satellites were accordingly conducted; these, in combination with a very accurate determination of the Vega trajectories using VLBI, allowed a flyby distance of 600 km to be achieved with only + or - 40 km uncertainty.

Muench, R. E.↗
NASA NTRS1986

In situ gas and ion measurements at comet Halley

The Giotto space probe's neutral mass spectrometer experiment has determined the abundances and the chemical, elemental and isotopic compositions of gases and low energy ions in the coma of comet Halley. Preliminary results show water predominating, at about 80 percent by volume, with a density of 4.7 x 10 to the 7th molecules/cu cm at 1000 km and a photodestruction scale length of 39,000 km. Limits on the abundances of CO2, NH3 and CH4 relative to H2O are also obtained. An ion temperature change observation indicates a contact surface location at 47,000 + or - 200 km.

Krankowsky, D.↗
NASA NTRS1986

Ion composition and dynamics at comet Halley

The Giotto space probe's ion mass spectrometer has obtained data on the composition and velocity distributions of cometary ions at distances of between 7.5 million and 1300 km from the comet Halley nucleus. Solar wind He(2+) was found throughout the coma, as close as 5000 km, with the He(+) produced by charge exchange being within about 200,000 km. A pile-up of heavy cometary ions was found at about 10,000 km from the nucleus. Inside the contact surface, which was found at about 4600 km, ion temperatures as low as about 340 K and outflow velocities of about 1 km/sec were found.

Balsiger, H.↗
NASA NTRS1986

Dust density and mass distribution near comet Halley from Giotto observations

The density and the mass spectrum of the dust near comet Halley have been measured by the Giotto space probe's dust impact detection system. The dust spectrum obtained at 291,000 km from the comet nucleus show depletion in small and intermediate masses; at about 600 km from the nucleus, however, the dust activity rises and the spectrum is dominated by larger masses. Most of the mass striking Giotto is noted to reside in the few large particles penetrating the dust shield. Momentum balances and energy considerations applied to an observed deceleration suggest that a large mass of the spacecraft was detached by an impact.

Mcdonnell, J. A. M.↗
NASA NTRS1986

Status of advanced propulsion for space based orbital transfer vehicle

A new Orbital Transfer Vehicle (OTV) propulsion system will be required to meet the needs of space missions beyond the mid-1990's. As envisioned, the advanced OTV will be used in conjunction with Earth-to-orbit vehicles, Space Station, and Orbit Maneuvering Vehicle. The OTV will transfer men, large space structures, and conventional payloads between low Earth and higher energy orbits. Space probes carried by the OTV will continue the exploration of the solar system. When lunar bases are established, the OTV will be their transportation link to Earth. NASA is currently funding the development of technology for advanced propulsion concepts for future Orbital Transfer Vehicles. Progress in key areas during 1986 is presented.

Cooper, L. P.↗
NASA NTRS1985

A preliminary look at the dust in Comet Halley

Highlights of infrared observations of the dust are discussed and compared with first results from the space probes. An emission feature was detected at 3.4 microns; the 10 and 20 micron silicate features were well-observed; and far-infrared data out to 160 micron were obtained. Organic material seems to be abundant in grains and may explain the 3.4 micron emission. Calculations are presented for one example of organic material. A component of the grains may volatize at temperatures around 300 K.

Hanner, M. S.↗