Gaia is a cornerstone mission in the science programme of the EuropeanSpace Agency (ESA). The spacecraft construction was approved in 2006, following a study in which the original interferometric concept was changed to a direct-imaging approach. Both the spacecraft and the payload were built by European industry. The involvement of the scientific community focusses on data processing for which the international Gaia Data Processing and Analysis Consortium (DPAC) was selected in 2007. Gaia was launched on 19 December 2013 and arrived at its operating point, the second Lagrange point of the Sun-Earth-Moon system, a few weeks later. The commissioning of the spacecraft and payload was completed on 19 July 2014. The nominal five-year mission started with four weeks of special, ecliptic-pole scanning and subsequently transferred into full-sky scanning mode. We recall the scientific goals of Gaia and give a description of the as-built spacecraft that is currently (mid-2016) being operated to achieve these goals. We pay special attention to the payload module, the performance of which is closely related to the scientific performance of the mission. We provide a summary of the commissioning activities and findings, followed by a description of the routine operational mode. We summarise scientific performance estimates on the basis of in-orbit operations. Several intermediate Gaia data releases are planned and the data can be retrieved from the Gaia Archive, which is available through the Gaia home page.

The Gaia mission

http://www.astro.sunysb.edu/metchev/PHY688/Pollack_etal96_core_accretion.pdf

Formation of the Giant Planets by Concurrent Accretion of Solids and Gas

We construct size distributions for carbonaceous and silicate grain populations in different regions of the Milky Way, LMC, and SMC. The size distributions include sufficient very small carbonaceous grains (including polycyclic aromatic hydrocarbon molecules) to account for the observed infrared and microwave emission from the diffuse interstellar medium. Our distributions reproduce the observed extinction of starlight, which varies depending on the interstellar environment through which the light travels. As shown by Cardelli, Clayton, and Mathis in 1989, these variations can be roughly parameterized by the ratio of visual extinction to reddening, RV. We adopt a fairly simple functional form for the size distribution, characterized by several parameters. We tabulate these parameters for various combinations of values for RV and bC, the C abundance in very small grains. We also find size distributions for the line of sight to HD 210121 and for sight lines in the LMC and SMC. For several size distributions, we evaluate the albedo and scattering asymmetry parameter and present model extinction curves extending beyond the Lyman limit.

https://iopscience.iop.org/article/10.1086/318651/pdf

Dust Grain-Size Distributions and Extinction in the Milky Way, Large Magellanic Cloud, and Small Magellanic Cloud

▪ Abstract This review surveys the observed properties of interstellar dust grains: the wavelength-dependent extinction of starlight, including absorption features, from UV to infrared; optical lum...

https://www.ifa.hawaii.edu/users/reipurth/reviews/draine.pdf

Interstellar dust grains

Dust -acoustic waves in dusty plasmas

A new method for analyzing low velocity particle impacts

A trajectory sensor for sub-micron sized dust

The solar system is a natural laboratory, accessible by a variety of methods, for studying the astrophysics of dust. Astronomical measurements mostly at visible and infrared wavelengths, yield the large-scale distribution of dust and its average composition. Examining natural surfaces deployed to the space environment, and assessing those surfaces’ micro-crater distributions, reveals the size distribution of dust. Meteor observations and their corresponding measurements provide orbital information of dust grains and their genetic interrelation to the larger bodies in our solar system: comets and asteroids. From analyses of meteorites and interplanetary dust particles collected in the stratosphere, we have a comprehensive understanding of the isotopic, elemental, and mineralogical composition of this primordial material. Finally, in situ dust analysis via dust detectors located in interplanetary space, the most versatile

Dust in Interplanetary Space and in the Local Galactic Environment

The stream particles are nanometer‐size dust particles ejected from the jovian and the saturnian systems with velocities greater than 100 kms−1. Due to their small size, stream particles are more sensitive to the electromagnetic force than to gravity. It has been shown by the simulations that the stream—particle dynamics in interplanetary space should be dominated by the interplanetary magnetic field (IMF) [15]. Based on the measurements by the dust detector on board the Cassini spacecraft, we found that the detection patterns of the stream particles are well correlated with the IMF structures. As the spacecraft crosses the compression regions of the Co—rotation Interaction Regions (CIRs), not only the directionality of the impacts changes with the field direction, but also the impact signal and rate vary with an increase of field strength. By understanding the interaction of stream particles and the solar wind, the data provide important insight to the formation environments of the stream particles and i...

Interaction of the solar wind and stream particles, results from the Cassini dust detector

The Munich Dust Counter (MDC) is a scientific experiment on board the MUSES-A mission of Japan measuring cosmic dust. The satellite HITEN of this mission has been launched on January 24th, 1990 from Kago-shima Space Center. Here the present status of the MDC experiment is summarized. The number of dust particles measured so far is presented together with first and preliminary results of flux calculations and spatial as well as directional distributions of cosmic dust particles measured until July 25, 1990. A clear evidence of particles coming from the inner solar system (beta-meteoroids) already has been found. These are compared to particles coming from the apex direction.

/pdf/the-present-status-of-the-munich-dust-counter-experiment-on-8ch0jhcb57.pdf

Eberhard Grün

Papers

A new method for analyzing low velocity particle impacts

A trajectory sensor for sub-micron sized dust

Dust in Interplanetary Space and in the Local Galactic Environment

Interaction of the solar wind and stream particles, results from the Cassini dust detector

The Present Status of the Munich Dust Counter Experiment on Board of the Hiten Spacecraft