During the July 31, 1981 solar eclipse, F-corona interferograms near MgI λ 5184 Å were obtained using a Fabry-Perot etalon (FPE) with an FWHM of 0.5 Å (corresponding to 30 km/sec) and an image tube. Radial velocities Vr of the interplanetary dust (i.d.) were measured in different directions.

Both prograde and retrograde motions of i.d. in the ecliptic region is discovered. Most of velocity values do not exceed 50 km/sec. A negative velocity component appears after averaging all Vr for all directions. Its average increases to − 20 km/sec toward the Sun. Some ejections are observed. The strongest (+ 130 km/sec) is located at the north ecliptic pole at a distance of 6 to 7 R⊙.

From the lack of unshifted Fraunhofer lines in the scattered sky light, we conclude that the sky brightness continuous component is predominant and its source is K-corona scattered light in the Earth’ s atmosphere.

Radial velocity measurements on the solar MgI 5183.618Å Fraunhofer absorption line in the Zodiacal Light spectrum have been made with a microprocessor-controlled servo-stabilised Fabry-Perot interferometer. Observations were made at 5 and 10 degree intervals in the ecliptic plane between morning and evening elongations of 25 degrees. These new data are of much greater precision and coverage than any previously obtained. Obtained over a two year period, the observations show a consistent evening/morning asymmetry in the radial velocity curve with the Gegenschein receding from the Earth at 4 Km/sec. These data do not support the hypothesis that the majority of interplanetary dust grains are in hyperbolic trajectories.

At the Pic-du-Midi Observatory, we have started a program to observe the spectrum of the zodiacal light in the region of the b absorption lines of MgI. We use a 1 meter spectrograph with a holographic grating followed by a focal reducer to obtain a 19 Å/mm dispersion over the micro-channel plate camera. Calibrated spectra obtained with an exposure time of 10 minutes systematically show earth atmospheric emission lines attributed to both NI and OH. The temporal variability of these emissions prevents an accurate determination of the line profiles. Our best processed measurements of Doppler shifts obtained during five nights do not allow to descriminate between circular and hyperbolic orbits of the interplanetary dust.

We are gaining an increased awareness and understanding of Earth-orbiting space debris. Meteoroid experiments in near-Earth orbit must therefore now be able to differentiate between interplanetary meteoroids and space debris. Space debris impacts are not thought, however, to have significantly affected near-Earth meteoroid measurements carried out in the early 1960’s. New experimental evidence also makes it appear very probable that most impact pits on lunar rocks with pit diameters smaller than 7 micrometers have been generated by lunar secondary ejecta impacts, and not by primary meteoroid impacts. In addition, ages determined from solar flare tracks in lunar rocks are not considered secure. Lunar crater production rates are more reliably deduced from meteoroid space experiments and not from solar flare track ages. When all of the above qualifications are taken into account, however, a rather satisfactorily self-consistent meteoroid flux versus mass distribution is obtained.

The Meteoroid Bumper Experiment on Explorer 46 (launched 1972) was placed in Earth orbit to evaluate the effectiveness of using double-wall structures against meteoroids. This paper re-examines the data from this experiment. Certain sets of sensors were found to be penetrated much more frequently than other sets. The most plausible explanation is that nearly all of the penetrations were from an Earth orbiting population of particulates. In addition, because a large percentage of the penetrations occured soon after solid rocket motors were fired in space, the particulates are most likely 75 μm diameter aluminum oxide. Aluminum oxide particulates are a major exhaust product from solid rocket motors. The size of particulates from most current solid rocket motors is found to range between 0.1 μm to 20 μm. Modeling the orbits of particulates from these rockets predicts that measurements in Earth orbit of interplanetary dust in this size range are also likely to include Earth orbiting particulates from solid rocket motors.

The data of studying meteoric particles on Elektron-1 and Elektron-3 space vechicles were processed in a new way which made it possible to get the first idea of the Earth’s dust envelope structure. Meteoric matter is distributed in it not unformly, but as aggregations of particles moving around the Earth in more or less stable orbits at certain distances from the Earth’s surface.

The in situ dust detectors on board the Helios spaceprobes detected impacts of micrometeoroids between 0.3 AU and 1 AU distance from the sun. Among the measured quantities were mass, impact speed and flight direction of the dust particles. Radial variations of the flux, azimuthal distribution and impact speed are discussed. Significantly different results were obtained for the “apex” particles observed by both ecliptic and south sensors and for the “eccentric” particles detected only by the south sensor. The radial spatial density variation of the “eccentric” particles is compatible with that derived for zodiacal light particles. Whereas the spatial density of “apex” particles peaks at 0.5 to 0.6 AU. From the measured quantities probability distributions of orbital elements were derived for the observed micrometeoroids. About 60% of the observed micrometeoroids (“apex” particles) are on low energy orbits (a ≲ 0.6 AU). About 30% of the particles (“eccentric” particles) had high energy orbits (a ≳ 0.9 AU). More than 10% of the observed particles show high probabilities for travelling on hyperbolic orbits.

The impact-ionization-detectors for the Galileo-/ISPM-Missions were calibrated using about 7000 iron particles with speeds between 1 km/s and 67 km/s and masses between 10−15 g and 2 × 10−10 g. These calibrations showed that the impact charge (Q) was proportional to the particle mass (m) at a fixed velocity. The speed dependent charge yield (Q/m) showed significant deviations (up to one magnitude) from a power law.

There are three independent methods (risetimes of electron and ion pulses, amplitude ratio between channeltron and ion pulse) for measuring particle speed and two possibilities (charge yields of electron and ion pulses) for mass measurement. This calibration showed that the speed can be determined within a factor of 1.2 and the mass within a factor of 2.0.

The Long Duration Exposure Facility was launched for the first time on April 6, 1984 by the NASA space shuttle Challenger. An array of solid-state detectors record the arrival time and approximate direction of an impacting particle. Two levels of detector sensitivity provide an indication of particle energy and mass. The active area is nearly 1 m2. We therefore expect count rates of about 30 per day over an exposure time of about a year. The orbit of the particle cannot be obtained, except statistically. We know the orientation of the detector, the position of LDEF in earth orbit, and the position of the earth in relation to other celestial bodies. From this information we can extract essential orbit information.

An earlier flight on the Explorer 46 satellite gave first evidence of the existence of submicron-sized particles, mostly associated with fresh meteor streams. We hope to obtain more precise data and estimate lifetimes in interplanetary space.

To study the fate and origin of IP (interplanetary) dust, we measure various kinds of time variations. Among the most interesting is the secular variation, i.e., the flux in various meteor streams, as a function of the passage of a comet.

One of the challenging problems will be to distinguish IP dust from man-made space debris. The separation will depend on knowing something of the orbits of debris. Probably more important will be the chemical analysis of the particles. The two types of information are in a sense complementary.

A passive interplanetary dust collection experiment, currently in orbit aboard LDEF (Long Duration Exposure Facility), is described. The collectors, germanium target plates covered by metallized Mylar foils, are designed for secondary ion mass spectrometry (SIMS) measurements of the elemental and isotopic compositions of residues resulting from micrometeoroid (> 10−10 grams) impacts. Impact simulation experiments have demonstrated the validity of the collection concept. Quantitative elemental analyses are complicated by the non-uniform distribution of projectile-derived elements.

The Long Duration Exposure Facility (LDEF-I), which contains a number of cosmic dust experiments, is due to be launched in the spring of 1984 and recovered about a year later. Current plans call for re-fitting the LDEF spacecraft with a large area of plastic nuclear track detectors and relaunching (LDEF-II) for a flight that will last about 2 years. The main purpose of the mission is to extend primary cosmic ray abundance measurements to the actinide region. A meeting was held at Washington University in December 1983 to discuss the problems and prospects for cosmic dust experiments on LDEF-II. Most participants were drawn from the LDEF-I community of investigators. The meeting resulted in a report which treated the scientific rationale for LDEF-II dust experiments, discussed various implementation options, and concluded with a set of summary recommendations. We discussed this report and summarized the status of LDEF-II as of this meeting. It is important to note that the report serves equally well as a basis for discussion of dust experiments on future space stations.

An active detector is described which recently has been developed for laboratory impact measurements and which already has been proposed for cosmic dust flight experiments. The detector consists of a very thin penetration foil and an impact plate. By means of piezo detectors the elastic-wave propagation times between the impact location and the piezo detectors can be measured in the foil and in the target. The evaluation of these signals gives the time of the event, the impact location, the projectile velocity, the flight path direction and at least the order of magnitude of mass of the impacting particle. This type of sensor will meet all requirements for particle detection in the diameter range from a few microns (dust particles) up to approx. a few millimeters (space debris) at all velocities. Small-sized projectiles can be detected by sensitive amplifiers. Low-energy electronics including data storage can be used for triangulation and impact time calculation. First experimental results which have been achieved in the Munich Accelerator Facilities will be presented.

The problem in the determination of impact particle parameters from hypervelocity impact damage on a foil or multilayer structure is one which deserves close attention in the era of ready access to recovered space impact events. In the MFE experiment (McDonnell et al 1984), we chose metallic foils, and this paper addresses the decoding of perforations in metallic foils, primarily of aluminium of typical dimensions 5 μm (hard temper rolled). Data is examined to establish for the first time a penetration relationship which extends over:

1. 1. marginal and thin sheet perforation;

2. 2. velocities varying from some 2 to 69 kms−1

3. 3. particle densities varying from some 1 g cm−3 (ices?) to 7.8 g cm−3 (iron?)

The relevance of the bulk density as a physical parameter characterizing interplanetary dust grains is discussed. The various measurements which lead to a determination of this parameter are reviewed. The specific case of the collected interplanetary dust grains is considered.

The bulk density of interplanetary dust grains has been and is still a matter of controversy. This quantity cannot, in general, be directly measured; it is used to relate the mass and the size of a grain. This duality stems from physics itself as there are interactions sensitive to the mass (e.g., gravitational forces) while others are sensitive to the size or the cross-section (e.g., light scattering, radiation pressure, gas and plasma interactions). The measuring technics of the grains reflect this duality as, for instance, impact sensors are generally sensitive to the kinetic energy and thus to the mass, while optical sensors are sensitive to the cross-section. One sees that the density is not strictly speaking the relevant parameter, but what is needed is a relationship between mass and average cross-section.

The quantitative study of the solar corona between 3 and 20 R⊙ is still a challenging task. Inherent difficulties are the proximity of the Sun and the still bright inner corona (< 3 R⊙), the low brightness of the outer corona and the low contrast of possible structures. A spinning, externally-occulted coronograph having its field-of-view limited to a sector of the corona presents several advantages over conventional coronographs for this study such as higher rejection of stray light and azimuthal uniformity over the whole field-of-view. Such an instrument could address the following aspects of the F-corona:

– photopolarimetry and colorimetry

– ellipticity, axis of symmetry

– temporal/spatial variations

– equatorial enhancements (rings)

– local component.

The collection of cosmic dust began in the middle of the last century with the recovery of spheres from the ocean floor and from Greenland ice (Murray and Renard 1891). The occurence of native metal in some of the deep sea spheres was the first clue that they were extraterrestrial. The deep sea spheres were described as “chondres” and their origin was attributed to the atmospheric melting of meteors. Polar ice and the ocean floor sediments often contain only minor amounts of magnetic terrestrial particles > 100μm and in these sites it is possible to collect rather large magnetic extraterrestrial particles that fell in historic times. In the intervening century an extensive series of particle searches were carried out in nearly all likely types of terrestrial collection sites. These included glaciers, islands, beaches, deserts, lakes, rooftops, rainwater, and all levels of the atmosphere up to low Earth orbit. Most of these efforts were not successful in collecting particles that were later proven to be extraterrestrial. In addition to the earlier deep sea and polar work, successful recoveries were made from a beach sand, a desert, and the stratosphere. All of these efforts are described in an excellent review by Hodge (1981).

Complementary analysis techniques including electron microscopy (SEM/EDX and TEM), molecular spectroscopy (FTIR and Raman), and secondary ion mass spectrometry (SIMS), are used to study individual dust particles collected in the stratosphere. Large deuterium enrichments and solar flare tracks show that most particles in the “chondritic” class are interplanetary dust particles (IDPs). Infrared transmission spectra of most IDPs fall into three major classes (layer-lattice silicates, pyroxenes and olivines). TEM and Raman measurements confirm this classification. The IR spectra show certain similarities to spectra observed in comets and protostars. In particular the 6.8 μm features observed in protostars and IDPs may have a common origin. Large D excesses are observed in IDPs of the first two IR classes. The correlation of D/H ratios with the C concentration indicates a carbonaceous carrier of the excess D. The D enrichments and IR spectra provide links to interstellar molecular cloud material.

Interplanetary dust particles (IDPs) collected in the stratosphere are thought to be mostly of cometary origin. They survived heating during their deceleration in the earth’s atmosphere (1). Because of their small size (< 50 μm ) and mass (< 10−7 g) they are difficult to analyse. Special preparation and examination methods have been developed for their investigations (2). We set out to study the trace-element-composition of these particles using the Heidelberg proton microprobe.

We present here a compendium of our laboratory measurements of the physical properties of submicronic particles made by some carbonaceous materials candidate as cosmic dust: amorphous carbon, silicon carbide. Comparison with data obtained by other authors is presented and discussed in view of astrophysical applications.

Recently, we found iron spherules with golden Ni-Fe core and silicate spherules with golden Ni-Fe inclusion in deep-sea sediments. This finding is of significance for further understanding of the origin of the deep-sea spherules.