Search NASA⌕ Search

SEARCH · Search NASA

Results for “comet flyby”

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 325 records · Page 18
All sourcesNASA NTRSDOE OSTI
NASA NTRS1994

Cometary coma chemical composition (C4) mission

Cometary missions are of enormous fundamental importance for many different space science disciplines, including exobiology. Comets are presumed relics of the earliest, most primitive material in the solar nebula and are related to the planetesimals. They undoubtedly provided a general enrichment of volatiles to the inner solar system (contributing to atmospheres and oceans) and may have been key to the origin of life. A Discovery class, comet rendezvous mission, the Cometary Coma Chemical Composition (C4) Mission, was selected for further study by NASA earlier this year. The C4 Mission is a highly focused and usefully-limited subset of the Cometary Rendezvous Asteroid Flyby (CRAF) Mission, concentrating exclusively on measurements which will lead to an understanding of the chemical composition and make-up of the cometary nucleus. The scientific goals of the Cometary Coma Chemical Composition (C4) Mission are to rendezvous with a short-period comet and (1) to determine the elemental, chemical, and isotopic composition of the nucleus and (2) to characterize the chemical and isotopic nature of its atmosphere. Further, it is a goal to obtain preliminary data on the development of the coma (dust and gas composition) as a function of time and orbital position.

Carle, G. C.↗
NASA NTRS1981

Plans for Comet Halley

The configuration, trajectories, and payloads of a spinning Earth-orbiting satellite designed by ESA for a post-perihelion flythrough (Giotto mission) of Comet Halley are described. Experiments approved for use on two identical three-axis stabilized Venera spacecraft destined to encounter the comet after releasing probes to Venus are listed as well as the instruments to be carried on Japan's Planet-A flyby mission. The main features launch windows are given for each spacecraft.

Rahe, J.↗
NASA NTRS2010

Millimeter and Submillimeter Observations of Comet 103P/Hartley 2

The close approach (0.12 AU) of Comet 103P/Hartley 2 to the Earth only S days prior to perihelion provides a unique opportunity to probe the chemical composition of this object. We will employ the Arizona Radio Observatory's Kitt Peak 12m (KPH12M) and the Submillimeter Telescope (SMT) for observations of multiple molecular species and their isotopologs towards the comet. There will also be an attempt to monitor this object during the EPOXI (Extrasolar Planet Observation. and Deep Impact Extended Investigation) flyby mission, which will obtain high resolution infrared spectra, for a comparison of the molecular inventory and a more accurate assessment of the abundances, sources (e.g. jets or cometismals), and chemistry.

Milan, S. N.↗
NASA NTRS1993

Giotto Ion Mass Spectrometer Measurements at Comet P/Grigg-Skjellerup

The Giotto Ion Mass Spectrometer High Intensity Spectrometer (IMS-HIS) measured fluxes of ions from about 260,000 km before (10:08:37 UT spacecraft time) to about 86,000 km after (17:01:33 UT spacecraft time) closest approach to comet P/Grigg- Skjellerup during the encounter on July 10, 1992. Although the HIS sensor was not designed to measure protons, the unusual flyby geometry at Grigg-Skjellerup allowed the sensor to detect these ions. Considerable temporal structure appears in the data, well- correlated with the data of other instruments onboard, especially those of the magnetometer. In particular, the proton count rate correlates with the direction of the magnetic field.

Rosenbauer, H.↗
NASA NTRS2006

Deep Impact Autonomous Navigation : the trials of targeting the unknown

On July 4, 2005 at 05:44:34.2 UTC the Impactor Spacecraft (s/c) impacted comet Tempel 1 with a relative speed of 10.3 km/s capturing high-resolution images of the surface of a cometary nucleus just seconds before impact. Meanwhile, the Flyby s/c captured the impact event using both the Medium Resolution Imager (MRI) and the High Resolution Imager (HRI) and tracked the nucleus for the entire 800 sec period between impact and shield attitude transition. The objective of the Impactor s/c was to impact in an illuminated area viewable from the Flyby s/c and capture high-resolution context images of the impact site. This was accomplished by using autonomous navigation (AutoNav) algorithms and precise attitude information from the attitude determination and control subsystem (ADCS). The Flyby s/c had two primary objectives: 1) capture the impact event with the highest temporal resolution possible in order to observe the ejecta plume expansion dynamics; and 2) track the impact site for at least 800 sec to observe the crater formation and capture the highest resolution images possible of the fully developed crater. These two objectives were met by estimating the Flyby s/c trajectory relative to Tempel 1 using the same AutoNav algorithms along with precise attitude information from ADCS and independently selecting the best impact site. This paper describes the AutoNav system, what happened during the encounter with Tempel 1 and what could have happened.

impactor spacecraft↗
NASA NTRS2004

Stardust Encounters Comet 81P/Wild 2

Stardust successfully encountered comet 81P/Wild 2 on 2 January 2004 at a distance of 236.4 +/- 1 km. All encounter investigations acquired valuable new and surprising findings. The time-of-flight spectrometer registered 29 spectra during flyby and measured the first negative ion mass spectra of cometary particles. The dust detectors recorded particles over a broad mass range, 10(exp -11) to 10(exp -4) g. Unexpectedly, the dust distribution along Stardust's flight path was far from uniform, but instead occurred in short 'bursts', suggesting in-flight breakup of fragments ejected from the nucleus. High-resolution, stunning images of the Wild 2 surface show a diverse and complex variety of landforms not seen from comets 1P/Halley and 19P/Borrelly or icy satellites of the outer solar system. Longer-exposure images reveal large numbers of jets projected nearly around the entire perimeter of the nucleus, many of which appear to be highly collimated. A triaxial ellipsoidal fit of the Wild 2 nucleus images yields the principal nucleus radii of 1.65 X 2.00 X2.75 km (+/- 0.05 km). The orientations and source locations on the nucleus surface of 20 highly collimated and partially overlapping jets have been traced. There is every indication that the expected samples were successfully collected from the Wild 2 coma and are poised for a return to Earth on 15 January 2006.

Stardust mission↗
NASA NTRS1986

Numerical simulation of spacecraft charging by impact-induced plasmas during a cometary flyby

A numerical model is developed for the interaction of a cometary probe, such as Giotto, with its environment, i.e., dust particles and gas. The spacecraft was set on a course to pass the comet at a velocity of 69 km/sec, so a chance existed that a potential field would form around the spacecraft and block lower energy particles from reaching the spacecraft instruments. The motion of electrons and ions is traced as a function of time to examine the evolution of the electric field, electric potential and the total space charge distributions on the surface of the spacecraft and its environment. Account is taken of the density of the particles and gas molecules at various distances from the comet, the collision energies involved, and the Giotto geometry. A solution is defined for the Poisson equation to describe the evolution of the plasma around Giotto, including the effects of ion collisions with the Al bumper protecting the spacecraft. The simulation predicts formation of an ion wake behind Giotto and the evolution of a positive potential on the order of 10 V around the spacecraft, i.e., sufficient for a positive potential barrier near the surface of the spacecraft.

Thiemann, H.↗
NASA NTRS1988

Low launch-energy trajectories to the outer solar system via Venus and earth gravity-assist flybys

Recent cancellation of the program to develop a Centaur upper stage for use in the Space Transportation System (STS) has motivated considerable interest in trajectory modes with low launch-energy requirements to the outer solar system. Flyby encounters of the inner planets, especially Venus and earth, may be used to enable missions to Jupiter, Saturn, and a restricted class of comets. An examination of mission opportunities to these targets is presented through the end of this century using gravity-assist trajectories.

Diehl, Roger↗
NASA NTRS1971

Guidance and navigation requirements for unmanned flyby and swingby missions to the outer planets. Volume 4: High thrust mission, part 2, phase C

The guidance and navigation requirements for a set of impulsive thrust missions involving one or more outer planets or comets. Specific missions considered include two Jupiter entry missions of 800 and 1200 day duration, two multiple swingby missions with the sequences Jupiter-Uranus-Neptune and Jupiter-Saturn-Pluto, and two comets rendezvous missions involving the short period comets P/Tempel 2 and P/Tuttle-Giacobini-Kresak. Results show the relative utility of onboard and Earth-based DSN navigation. The effects of parametric variations in navigation accuracy, measurement rate, and miscellaneous constraints are determined. The utility of a TV type onboard navigation sensor - sighting on planetary satellites and comets - is examined. Velocity corrections required for the nominal and parametrically varied cases are tabulated.

Source record↗
NASA NTRS1994

Cometary Coma Chemical Composition (C4) Mission

Cometary exploration remains of great importance to virtually all of space science. Because comets are presumed to be remnants of the early solar nebula, they are expected to provide fundamental knowledge as to the origin and development of the solar system as well as to be key to understanding of the source of volatiles and even life itself in the inner solar system. Clearly the time for a detailed study of the composition of these apparent messages from the past has come. A comet rendezvous mission, the Cometary Coma Chemical Composition (C4) Mission, is now being studied as a candidate for the new Discovery program. This mission is a highly-focussed and usefully-limited subset of the Cometary Rendezvous Asteroid Flyby (CRAF) Mission. The C4 mission will concentrate on measurements that will produce an understanding of the composition and physical makeup of a cometary nucleus. The core science goals of the C4 mission are 1) to determine the chemical, elemental, and isotopic composition of a cometary nucleus and 2) to characterize the chemical and isotopic nature of its atmosphere. A related goal is to obtain temporal information about the development of the cometary coma as a function of time and orbital position. The four short-period comets -- Tempel 1, Tempel 2, Churyumov-Gerasimenko, and Wirtanen -which all appear to have acceptable dust production rates, were identified as candidate targets. Mission opportunities have been identified beginning as early as 1998. Tempel I with a launch in 1999, however, remains the baseline comet for studies of and planning the C4 mission. The C4 mission incorporates two science instruments and two engineering instruments in the payload to obtain the desired measurements. The science instruments include an advanced version of the Cometary Ice and Dust Experiment (CIDEX), a mini-CIDEX with a sample collection system, an X-ray Fluorescence Spectrometer and a Pyrolysis-Gas Chromatograph, and a simplified version of the Neutral Gas and Ion Mass Spectrometer (NIGMS). Both of these instruments have substantial heritage as they are based on those developed for the CRAF Mission. The engineering instruments include a simplified Comet Dust Environmental Monitor (SCODEM) and a navigational Camera, NAVCAM. While neither of the instruments will be permitted to establish science requirements, it is anticipated that significant science return will be accomplished Radio science will also be included.

Carle, Glenn C.↗
NASA NTRS1978

Asteroid mission alternatives

The options for asteroid missions are evaluated within the constraints of existing or planned launch vehicles and low-thrust propulsion systems. A wide variety of missions is possible, including flyby, rendezvous, and even sample return. The multi-asteroid rendezvous concept requires an ion drive low-thrust propulsion system of the type being developed for a comet rendezvous. It is indicated that there are plentiful opportunities for such missions to visit four asteroids with stay times of 60-90 days each and with transit times between rendezvous of the order of a year.

Niehoff, J. C.↗
NASA NTRS1984

Through the tail of a comet

The instrumentation, trajectory, and missions of the ISEE-3 spacecraft being sent to observe Comet Giacobini-Zimmer (GZ) are described. Originally parked at a libration point to observe the solar wind, ISEE-3 was directed to perform a complex series of flybys of the earth and the moon to move to a trajectory that will intersect the GZ tail in 1985. Renamed ICE, the spacecraft will record magnetic field and charged particle data on the interaction of the cometary tail with the solar wind.

Mclaughlin, W. I.↗
NASA NTRS1992

Planetary missions using microspacecraft technology

Some of the planetary missions using microspacecraft of mass on the order of 10 kg which are presently being considered at JPL are discussed. The primary benefits offered by this type of spacecraft is the small and relatively inexpensive launch vehicles and short program development schedules. A mission presently considered by the Asteroid Investigation with Microspacecraft (AIM) study is described with special attention given to the spacecraft configuration; the AIM mission will launch three spacecraft from a single Pegasus vehicle, achieving separate flybys for three near-earth asteroids. Attention is also given to the salient features of the Mars Rover Sample Return mission, the Venus Atmospheric Sounder, and the Comet Nucleus Mission, for which the application of microspacecraft technology is considered.

Short, Kendra L.↗
NASA NTRS1986

Comet coma sample return

The feasibility of capturing comet dust with polymer foam, dense gas, and fiber collectors is discussed. Polystyrene foams seem suitable. For volatile capture, chemically active getters are suggested. A scenario for a low speed flyby sample return mission is outlined.

Tsou, P.↗
NASA NTRS1986

Dust particles detected near Giacobini-Zinner by the ICE plasma wave instrument

During the ICE flyby of Giacobini-Zinner the plasma wave instrument detected numerous impulsive signals caused by dust impacts on the spacecraft. Most of the impacts occurred within 30,000 km of the comet. The impact rate averaged over the inbound and outbound legs varies approximately as 1/r-squared, as would be expected for an isotropic constant velocity radial outflow. Small differences between the inbound and outbound legs exist which may be indicative of azimuthal variations in the dust production rate. A simple model of the impact ionization and charge collection by the antenna indicates that the particles have a mass on the order of 10 to the -12 to 10 to the -10th gm, corresponding to particles with radii of a few microns.

Gurnett, D. A.↗
NASA NTRS1971

Guidance and navigation requirements for unmanned flyby and swingby missions to the outer planets. Volume 1: Summary report

Unmanned spacecraft missions to the outer planets are of current interest to planetary scientists, and are being studied for the post 1970 time period. Flyby, entry and orbiter missions are all being considered using both direct and planetary swingby trajectory modes. The navigation and guidance requirements for a variety of missions to the outer planets and comets including both the three and four planet Grand Tours, are summarized.

Source record↗
NASA NTRS2011

Centimeter, Millimeter, and Submillimeter Observations of Comet l03P/Hartley 2

The close approach (0.12 AU) of Comet 103P/Hartley 2 to the Earth only 8 days prior to perihelion provided a unique opportunity to probe the chemical composition of this object. Additionally, supporting data was acquired during the EPOXI (Extrasolar Planet Observation and Deep Impact Extended Investigation) flyby mission [1], which provided high resolution infrared spectra and images. Observations were conducted from four facilities, contributing to the large ground-based consortium organized in support of the EPOXI mission [2]. The Arizona Radio Observatory's 12m telescope, Kitt Peak, AZ, and Submillimeter telescope, Mt. Graham, AZ, as well as the James Clerk Maxwell Telescope, Mauna Kea, HI and the Greenbank 100m telescope, Greenbank, WV, were employed for this study covering 20 cm, 3 cm, and 0.8-3 mm. Data were obtained, collectively, from 12 October 2010 to 5 November 2010 [3]. HCN, CH3OH, H2CO, HNC, OH, and CS were detected, and upper limits on the abundance of H2S, SO2, c-C3H2, and deuterated isotopologues of HCN, H2CO, and H2O were measured. Upper limits on the D/H ratio derived from DCN gave D/H less than 0.01[3]. Detailed analysis of these data will help constrain the temperature, abundances, variance or periodicity of a given species, and can be compared to results from other comets, as well as support the data obtained from the EPOXI mission. The full analysis and comparison will be presented.

Milam, Stefanie N.↗
NASA NTRS1989

Ballistic comet exploration mission options

To attain the fundamental goals of cometary exploration, rendezvous and sample return missions are necessary. This paper investigates various trajectory options and provides a comprehensive set of mission opportunities available for launches in the 1990s. The modes of explorations considered are rendezvous and flybys with atomized-sample-return missions. For each type of exploration, the paper describes various classes and modes of trajectories available, their inherent characteristics, and the techniques of identifying useful trajectories. The energy requirement associated with these missions and the performance possibilities are provided.

Yen, Chen-Wan L.↗