[Show abstract][Hide abstract] ABSTRACT: The Cassini-Huygens Cosmic Dust Analyzer (CDA) is intended to provide direct observations of dust grains with masses between 10<sup>-19</sup> and 10<sup>-9</sup> kg in interplanetary space and in the jovian and saturnian systems, to investigate their physical, chemical and dynamical properties as functions of the distances to the Sun, to Jupiter and to Saturn and its satellites and rings, to study their interaction with the saturnian rings, satellites and magnetosphere. Chemical composition of interplanetary meteoroids will be compared with asteroidal and cometary dust, as well as with Saturn dust, ejecta from rings and satellites. Ring and satellites phenomena which might be effects of meteoroid impacts will be compared with the interplanetary dust environment. Electrical charges of particulate matter in the magnetosphere and its consequences will be studied, e.g. the effects of the ambient plasma and the magnetic field on the trajectories of dust particles as well as fragmentation of particles due to electrostatic disruption.
Space Science Reviews 08/2004; 114(2004):465-518. DOI:10.1007/s11214-004-1435-z · 6.28 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Interplanetary dust missions like Stardust and Cassini-Huygens carry dust detectors which are able to determine the elemental composition of micro-meteorites. These dust detectors are time-of-flight mass spectrometers which analyse the plasma generated upon hypervelocity impacts. In order to analyze the data of these missions, simulations in the laboratory are necessary. The Heidelberg dust accelerator facility was used to shoot micron sized carbon and latex particles on the engineering models of the space experiments. The mass spectra achieved show sequences of broad peaks which are attributed to cluster ions of hydrocarbons. The overall charge yield of the impacts and the relative abundances of these cluster ions was investigated.
Advances in Space Research 01/2004; 33(8):1289-1293. DOI:10.1016/j.asr.2003.05.034 · 1.36 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: This paper presents the results of the hypervelocity projectile bombardment of a gold-coated beryllium substrate telescope mirror. Individual latex (rho = 1.1 g/cm3) and iron (7.9 g/cm3) projectiles, in the size range 0.70 to 1.44mum (avg. mass = 0.24 - 7.1 x 10-15 kg), representative of interplanetary dust, with velocities from 2 - 20 km/s, created impact craters in the composite mirror structure that were approximate hemispheres. The ratio of impact damage diameter to projectile energy was found experimentally to be close to 0.1mum/nJ for both latex and iron projectiles. These dimension data, combined with recent measurements of interplanetary and interstellar dust fluxes, can be used to estimate expected space telescope mirror surface damage and scattering increase due to hypervelocity dust impacts.
Proceedings of SPIE - The International Society for Optical Engineering 01/2004; 5487. DOI:10.1117/12.552236 · 0.20 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The Cosmic Dust Analyser (CDA) was launched onboard CASSINI in October 1997 and started its operation in March 1999. The measurement of the dust properties mass (10-15 - 10-9 g ), electric charge (10-15 - 10-12 C ), chemical composition (mass resolution 20-50) and speed (1-100 km s-1 ) is accomplished by using impact ionisation. A High Rate Detector (HRD) is used to detect high impact rates. In the last last years, CDA was operated successfully and measured interstellar and interplanetary micrograins. CDA measured the charge of micrograins and detected time-of-flight mass spectra of interplanetary and Jovian stream particles. After 3 years in operation, the calibration status of CDA is discussed and a comparison with the Galileo and Ulysses dust instruments is given. The limits of the calibration are discussed and an outlook is given about future activities.
[Show abstract][Hide abstract] ABSTRACT: The pn-CCD is the focal plane detector of one of the three X-ray telescopes aboard the XMM-Newton observatory. During revolution #156 more than 30 individual bright pixels lightened up out of approximately 150,000 pixels of the 6 cm × 6 cm large detector area. The amount of leakage current generated in the pixels cannot be explained by single heavy ions impact, however. We suggest that a micrometeoroid scattered off the mirror surface under grazing incidence reached the focal plane detector and produced the bright pixels. This proposal was studied by us experimentally at the Heidelberg dust accelerator. Micron-sized iron particles were accelerated to speeds of the order of 5 km/s impinging on the surface of an X-ray mirror under grazing incidence. Scatter products have been found with detectors placed behind the mirror. They have been analyzed by various methods to characterize their properties and the effects produced by them in the pn-CCD. Micrometeoroid damage to semiconductor detectors in the focus of grazing incidence optics might be of concern for future space projects with very large collecting area and are proposed to be studied in detail.
Proceedings of SPIE - The International Society for Optical Engineering 03/2003; DOI:10.1117/12.461154 · 0.20 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Dust measurements by the instruments on the Ulysses and Galileo spacecraft outside 3 AU heliocentric distance revealed a collimated source of interstellar particles. Here we report about the successul in-situ measurement of interstellar dust particles within the inner solar system by the Cosmic Dust Analyzer (CDA) aboard the Cassini/Huygens spacecraft. The CDA instrument is similar to the Galileo and Ulysses detectors and its function is based upon hypervelocity impact ionization. The dust impact generates an impact plasma and the amount of negative and positive charge is measured. An analysis of the ion charge signals together with geometric and kinematic considerations allowed a separation of interplanetary from interstellar particles. The interstellar flux measured by Cassini at 0.8 AU is in good agreement with the flux measured by Ulysses at 3 AU at the same time. The simultaneous detection of interstellar grains at 3 AU and 0.8 AU prove that big interstellar grains are able to penetrate deeply into the inner solar system.
[Show abstract][Hide abstract] ABSTRACT: The Cosmic Dust Analyser (CDA) was launched onboard CASSINI in October 1997 and started its operation in March 1999. In the last two years, CDA was operated successfully and measured interstellar and interplanetary micrograins. CDA measured charge signals of dust impacts and achieved time-of-flight mass spectra of interplan- etary and jovian dust stream particles. This paper gives an overview of the current results.
[Show abstract][Hide abstract] ABSTRACT: The Cosmic Dust Analyzer (CDA) is an instrument that measures the
physical and chemical properties of micrometer-sized dust particles on
board the CASSINI- HUYGENS spacecraft to Saturn. The instrument
determines the velocity, electric charge, mass and chemical constitution
of interplanetary and interstellar dust parti- cles. With the newly
developed dust particle source at the Heidelberg 2 MV-particle
accelerator we had the possibility to use various materials,
representing different me- teorite classes, as projectiles for the
calibration of the CDA instrument. We accelerated iron, aluminium,
carbon, sodium-coated carbon and two kinds of latex particles with
grainsizes between 0.02 and 3.0 µm and to speeds ranging from 2 to
50 km/s. The work presented is limited to the time-of-flight mass
spectra obtained from particle impacts on the rhodium target.
[Show abstract][Hide abstract] ABSTRACT: The Cosmic-Dust-Analyzer (CDA) onboard Cassini performs in-situ measurements of micron sized Cosmic Dust (Interstellar dust, interplanetary dust, Saturnian dust). The speed (1-100 km/s), mass (10e-15 - 10e-9 g), charge (fC - pC) and chemical composition of the particles can be determined by CDA. This paper presents the timeof-flight spectra of hypervelocity impacts of organic latex particles achieved at the Heidelberg dust accelerator facility. These spectra are compared with in-flight spectra of the CDA-Cassini cruise measurements at distances between 1 and 5 AU.
[Show abstract][Hide abstract] ABSTRACT: The mirror systems of the X-ray observatory XMM-Newton were designed to image X-rays up to 15 keV by grazing incidence reflection onto a focal plane, equipped with Charge Coupled Devices (CCDs). In orbit # 156 we have observed a sudden increase of about 35 ``bright'' pixels spread over 15 cm2 in the pn-CCD camera system. The amount of locally generated leakage current cannot be explained by ionizing particles. We suggest that a micrometeoroid scattered under a small angle off the X-ray telescope mirror surface finally reached the focal plane detector and produced the damage.
Astronomy and Astrophysics 08/2001; 375(1). DOI:10.1051/0004-6361:20010916 · 4.38 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Cosmic dust, consisting of micrometeoroids with grain sizes below , is investigated in situ with impact ionisation detectors on spacecraft measuring the electric charge of the ions produced by the impact of a particle at a speed above . Time-of-flight mass spectrometers incorporated into the detectors determine the chemical components of an impacting projectile. To calibrate the dust detector instruments particles with similar compositions and speeds as the expected micrometeoroids are needed as projectiles in the laboratory. The Heidelberg dust accelerator, a electrostatic accelerator, equipped with a special dust particle source, provides micrometer-sized particles as projectiles for hypervelocity impact experiments.In this paper, we describe a new dust source that has been developed to expand both, the charge and impact speed ranges, and to use various projectile materials. We present the results of accelerating particles with grain sizes between 0.02 and , made from metals, carbon, and polymer-coated latex using the new dust source at the accelerator and at a test setup with acceleration voltage. With this dust source we achieved also a higher charging of iron particles ( for a particle) than with our old source (), resulting in speeds up to for a particle of size, and for a particle of size.
Planetary and Space Science 07/2001; 49(8-49):853-858. DOI:10.1016/S0032-0633(01)00035-6 · 1.88 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The expected Jupiter flyby of the Cassini spacecraft is on December 30 in the year 2000. This offers the possibility to observe and characterize the Jovian dust stream discovered by the dust detectors onboard Galileo and Ulysses. The flux is expected high enough to be observed at distances as far as almost 2 AU away from Jupiter. The dust stream particles originate in the plumes of Io's volcanoes. Theoretical analysis has shown that the size of the particles is in the range of 10 nm and the speed exceeds 200 km/s. The "Cosmic Dust Analyser" of Cassini offers now the unique opportunity to measure the elemental composition of these dust stream particles and hence the volcanic ash from Io.