Galileo dust data from the jovian system: 2000 to 2003 (original) (raw)
Related papers
Galileo dust data from the jovian system: 1997–1999
Planetary and Space Science, 2006
The dust detector system on board the Galileo spacecraft recorded dust impacts in circumjovian space during the craft's orbital mission about Jupiter. This is the eighth in a series of papers dedicated to presenting Galileo and Ulysses dust data. We present data from the Galileo dust instrument for the period January 1997-December 1999 when the spacecraft completed 21 revolutions about Jupiter. In this time interval data were obtained as high resolution realtime science data or recorded data during 449 days (representing 41% of the entire period), or via memory readouts during the remaining times. Because the data transmission rate of the spacecraft was very low, the complete data set (i.e. all parameters measured by the instrument during impact of a dust particle) of only 3% (7625) of all particles detected could be transmitted to Earth; the other particles were only counted. Together with the data of 2883 particles detected during Galileo's interplanetary cruise and 5353 particles detected in the jovian system in 1996, complete data of 15 861 particles detected by the Galileo dust instrument from 1989 to 1999 are now available. The majority of the detected particles were tiny grains (about 10 nm in radius), most of them originating from Jupiter's innermost Galilean moon Io. They were detected throughout the jovian system and the highest impact rates exceeded 100 min À1 (C21 orbit; 01 July 1999). With the new data set the times of onset, cessation and a 180 shift in the impact direction of the grains measured during 19 Galileo orbits about Jupiter are well reproduced by simulated 9 nm particles charged up to a potential of þ3 V, confirming earlier results obtained for only two Galileo orbits . Modeling the Galileo dust measurements at Jupiter. Geophys. Res. Lett. 24, 2175-2178. Galileo has detected a large number of bigger particles mostly in the region between the Galilean moons. The average radius of 370 of these grains measured in the 1996-1999 period is about 2 mm (assuming spherical grains with density 1 g cm À3 ) and the size distribution rises steeply towards smaller grains. The biggest detected particles have a radius of about 10 mm. r
Three years of Galileo dust data: ii. 1993–1995
Planetary and Space Science, 1998
Between January 1993 and December 1995 the Galileo spacecraft traversed interplanetary space between Earth and Jupiter and arrived at Jupiter on 7 December 1995. The dust instrument onboard the spacecraft was operating during most of the time and data from the instrument were obtained via memory readouts which occurred at rates between twice per day and once per week. All events were classified by an onboard program into 24 categories. Noise events were usually restricted to the lowest categories (class 0). During Galileo's passage through Jupiter's radiation belts on 7 December 1995 several of the higher categories (classes 1 and 2) also show evidence for contamination by noise. The highest categories (class 3) were noise-free all the time. A relatively constant impact rate of interplanetary and interstellar (big) particles of 0.4 impacts per day was detected over the whole three-year time span. In the outer solar system (outside about 2.6 AU) they are mostly of interstellar origin, whereas in the inner solar system they are mostly interplanetary particles. Within about 1.7 AU from Jupiter intense streams of small dust particles were detected with impact rates of up to 20,000 per day whose impact directions are compatible with a Jovian origin. Two different populations of dust particles were detected in the Jovian magnetosphere: small stream particles during Galileo's approach to the planet and big particles concentrated closer 1 Correspondence to: krueger@galileo.mpi-hd.mpg.de 1 to Jupiter between the Galilean satellites. There is strong evidence that the dust stream particles are orders of magnitude smaller in mass and faster than the instrument's calibration, whereas the calibration is valid for the big particles. Because the data transmission rate was very low, the complete data set for only a small fraction (2525) of all detected particles could be transmitted to Earth; the other particles were only counted. Together with the 358 particles published earlier, information about 2883 particles detected by the dust instrument during Galileo's six years' journey to Jupiter is now available. R. Galileo observes electromagnetically coupled dust in the jovian magnetosphere. -north and radial traverses through the zodiacal cloud. Icarus, 129, 270-288, 1997c Hamilton, D.P. and Burns, J.A., Orbital stability zones about asteroids II. The destabilizing effects of eccentric orbits and of solar radiation. Icarus 96, 43-64, 1992 Horányi, M., Grün, E., Heck, A. Modeling the Galileo dust measurements at Jupiter.
Space Science Reviews, 1992
The Galileo Dust Detector is intended to provide direct observations of dust grains with masses between 10 19 and 10 9 kg in interplanetary space and in the Jovian system, to investigate their physical and dynamical properties as functions of the distances to the Sun, to Jupiter and to its satellites, to study its interaction with the Galilean satellites and the Jovian magnetosphere. Surface phenomena of the satellites (like albedo variations), which might be effects of meteoroid impacts wilt be compared with the dust environment. Electric charges of particulate matter in the magnetosphere and its consequences will be studied; e.g., the effects of the magnetic field on the trajectories of dust particles and fragmentation of particles due to electrostatic disruption. The investigation is performed with an instrument that measures the mass, speed, flight direction and electric charge of individual dust particles. It is a multicoincidence detector with a mass sensitivity 106 times higher than that of previous in-situ experiments which measured dust in the outer solar system. The instrument weighs 4.2 kg, consumes 2.4 W, and has a normal data transmission rate of 24 bits s-1 in nominal spacecraft tracking mode. On December 29, 1989 the instrument was switched-on. After the instrument had been configured to flight conditions cruise science data collection started immediately. In the period to May 18, 1990 at least 168 dust impacts have been recorded. For 81 of these dust grains masses and impact speeds have been determined. First flux values are given.
Galileo observes electromagnetically coupled dust in the Jovian magnetosphere
Journal of Geophysical Research, 1998
Measurements of dust coupled to the Jovian magnetosphere have been obtained with the dust detector on board the Galileo spacecraft. We report on data obtained during the first four orbits about Jupiter that had fiybys of the Galilean satellites: Ganymede (orbits 1 and 2), Callisto (orbit 3), and Europa (orbit 4). The most prominent features observed are highly time variable dust streams recorded throughout the Jovian system. The impact rate varied by up to 2 orders of magnitude with a 5 and 10 hour periodicity, which shows a correlation with Galileo's position relative to the Jovian magnetic field. Around 20 Ra (Jupiter radius, Ra = 71,492 kin) in bound a dip in the impact rate has been found consistently. At the same times, reversals by 180 ø in impact direction occurred. This behavior can be qualitatively explained by strong coupling of nanometer-sized dust to the Jovian magnetic field. At times of satellite fiybys, enhanced rates of dust impacts have been observed, which suggests that all Galilean satellites are sources of ejecta particles. Inside about 20 Ra impacts of micrometer-sized particles have been recorded that could be particles on bound orbits about Jupiter. detected within 2 AU from Jupiter during Galileo's approach to the planet [Griin et al., 1996a]. It was immediately recognized that the magnetosphere of Jupiter would eject submicron-sized dust particles if they existed in the magnetosphere [Horanyi et al., 1993a,b; Hamilton and Burns, 1993]. At two places, dust in abundance had been discovered by Voyageras cameras before (1) the Jovian ring at 1.8 Rj (Jupiter radius, Rj = 71,492 km) and its weak extension out to 3 Rj [Showalter et al., 1995], and (2) Io's volcanic plumes, which reach heights of about 300 km above Io's surface [Collins, 1981]. Both phenomena have been suggested as the source of the dust streams. Electromagnetic interaction of the particles making up the dust streams was evident both in the Ulysses and Galileo data when both spacecraft were outside the Jovian magnetosphere: the arrival direction showed significant correlations with the ambient interplanetary magnetic field [Griin et al., 1993, 1996a]. Zook et al., [1996] demonstrated convincingly that only particles in the 10 nm size range would couple strongly enough to the interplanetary magnetic field to show the effects observed by Ulysses. Similar analysis of the Galileo data comes to the same result (J.C. Liou, private communication, 1997). The corresponding impact speeds were deduced to be in excess of 200 km/s. During Galileo's initial approach to Jupiter and Io, dust continuously impacted the dust detector system (DDS), but after Io closest approach, impacts of small particles ceased [Griin et al., 1996b]. A few larger particles were recorded within hours of Jupiter closest ap-20,011
Modeling the Galileo dust measurements at Jupiter
Geophysical Research Letters, 1997
We discuss our modeling that is aimed to reproduce the observed dust impact rates during the first two Ganymede encounters of Galileo. We use a detailed fields and particles model of the magnetosphere and simultaneously follow the dynamics and the charging history of small dust particles. We assume Io to be the only source of the escaping dust grains and show that our model matches the gross characteristics of the observations. We argue that the large scale dawn-todusk electric field can be responsible for shaping the emission pattern of dust from the Io plasma torus. The emission pattern shows a minimum flux toward the Sun, perhaps explaining why the observed fluxes did not increase as Galileo approached the source region of the dust particles. We show that the general shape of the trajectories of the grains offers a good explanation for the sudden shift in the observed direction of the dust impacts. Modeling the observed dust impact rates gives an excellent opportunity to test our particles and fields model of Jupiter's magnetosphere.
Observations of Electromagnetically Coupled Dust in the Jovian Magnetosphere
Astrophysics and Space Science, 1998
We report on dust measurements obtained during the seventh orbit of the Galileo spacecraft about Jupiter. The most prominent features observed are highly time variable dust streams recorded throughout the Jovian system. The impact rate varied by more than an order of magnitude with a 5 and 10 hour periodicity, which shows a correlation with Galileo's position relative to the Jovian magnetic field. This behavior can be qualitatively explained by strong coupling of nanometer-sized dust to the Jovian magnetic field. In addition to the 5 and 10 h periodicities, a longer period which is compatible with Io's orbital period is evident in the dust impact rate. This feature indicates that Io most likely is the source of the dust streams. During a close (3,095 km altitude) flyby at Ganymede on 5 April 1997 an enhanced rate of dust impacts has been observed, which suggests that Ganymede is a source of ejecta particles. Within a distance of about 25 RJ(Jupiter radius, RJ= 71,492 km) from Jupiter impacts of micrometer-sized particles have been recorded which could be particles on bound orbits about Jupiter.
Jovian atmospheric studies with the Galileo near infrared mapping spectrometer: An update
Advances in Space Research, 1999
In its first two years of operation since arrival at Jupiter in December 1995, the Near Infixed Mapping spectrometer (NIMS) on the Galileo orbiter spacecraft obtained extensive coverage of the planet, including detailed coverage of the north equatorial belt (NEB) 'hot spot' region and the Great Red Spot. We will present the current state of data analysis including recent results on the abundances and variability of several minor constituents (3320, C&, NH3, GeH4, CH3D and PH3) and the cloud structure and morphology.
Galileo Infrared Observations of Jupiter
Astrophysics and Space Science Library, 1997
Galileo infrared observations of Jupiter have been performed with two instruments, the Near Infrared Mapping Spectrometer (NIMS) and the Photo-Polarimeter Radiometer (PPR). A first data set was obtained at the time of the collision of comet Shoemaker-Levy 9 with Jupiter, in July 1994. Information was retrieved about the energy budget of the event, the penetration level of the explosion, the temperature and diameter of the fieball and its evolution with time, the temperature of the atmosphere heated by the infalling debris, and the amount of water formed after the explosion. The second set of data was recorded in 1996 after the Galileo probe entry. Evidence was found for a very low water abundance in the hot spots; this result is in full agreement with the conclusions derived from the Galileo probe. Infrared observations of the Great Red Spot allow to derive its 3-D structure, which appears compatible with the model of an anticyclonic vortex.
Jovian dust: streams, clouds and rings
2004
In situ dust detection; Jovian dust stream measurements: electromagnetically interacting dust, impact directions, Io's frequency signature, Io's dust contribution, monitoring Io's volcanic plumes, long-term monitoring of Jovian dust streams, Cassini-Galileo joint dust stream measurements; Jovian dust stream modeling and dynamics: modeling approach, dynamics and charging of dust, Jovian dust stream dynamics, sizes of dust ejected from the Jovian magnetosphere; Dust clouds surrounding the Galilean satellites: measurements, dynamics of grains in circumsatellite dust clouds; A faint dusty ring beyond Jupiter's gossamer rings: measurements, sources and dynamics of larger grains in orbits about Jupiter; Gossamer rings.