Overview. 1.1 Stripe Issuing Services and Stripe Issuing Programs.
Overview. Due to the importance of measuring the dust emitted from the comet nucleus, one of the essential instruments for the Rosetta mission is the Micro-Imaging Dust Analysis System (MIDAS), dedicated to the microtextural and statistical analy- sis of cometary dust particles. The instrument described in this paper is based on the technique of scanning force microscopy, which has made rapid progress in re- cent years. The instrument will for the first time image interplanetary and pristine cometary particles in the nm-μm range in 3D. It will also provide morphological and statistical information on the dust population, including texture, shape, size and flux. This paper describes the MIDAS scientific objectives dedicated to the collection of very small particles and the characterisation of materials by atomic force microscopy. Finally, it presents the technical solutions adopted for this in- augural implementation of the technique on a space mission and the capabilities as confirmed in the post-launch commissioning. To study the nature of cometary material is crucial and will provide important constraints on the true nature of the early solar nebula.
Overview. Riedler et al. (1998) documented the status of the investigation shortly after the se- lection for the Rosetta payload. At that time the key elements of the instrument had been defined, but the detailed design had only been started. The MIDAS instrument in its flight configuration consists of a single mechanical unit (Figure 4). The top part of the main box houses the elements of the AFM and the system to collect and transport the dust samples from the exposure position to the head of the microscope (Figure 5). The structure is made out of ribbed aluminium plates. A funnel-shaped dust intake system, which protrudes through the outer spacecraft wall, is attached to the upper part of the box. An external cover protects the internal elements against contamination during ground operations and launch. A shutter at the outer end of the funnel controls the exposure time of one facet at a time on the dust collector wheel inside the box. This wheel can be rotated and translated to transport the dust samples to one of 16 sensor elements (cantilevers) in the AFM after exposure. The array of cantilevers is fixed to the Z microscope stage, which is attached to the high-resolution XY positioning stage. All stages are driven by piezoelectric systems, and the displacements can be measured by a strain gauge and capacitive sensors. In addition, the voltages applied to the piezoelectric actuators provide the same displacement information through the respective calibration curves. To begin the imaging process, the XYZ-stage is brought into contact with the sample on the dust collector wheel by the approach mechanism. As soon as the selected cantilever senses contact with the sample (indicated by a deflection of the cantilever in contact mode, or a change of amplitude in dynamic mode), the scanning operation can start. After the measurement, the XYZ-stage has to be retracted, and another approach procedure has to be performed before the measurement on another area. The 16 available needles have slightly different characteristics and shapes, and four out of them are additionally sensitive to magnetic forces. The degradation of a needle dur- ing scanning and the available lifetime very much depend on the operating param- eters and the sample. The selection of a particular needle is achieved by moving the linear stage to position the dust collector wheel in front of the respective cantilever. As the measurements by the AFM are sensitive to microvibrations induced by other active ...
Overview. The robotics system ensures that dust particles are collected on a predetermined surface area and transported in a controlled manner to the AFM’s scanner head. Its (Continued on next page) Figure 6. (Continued). elements are on a rigid base plate that connects with the outer housing through a mechanical damping system. Three motions are required: . a rotation to bring the exposed area of the dust collector wheel in front of the scanner head, . a linear translation of the collector wheel of up to 30 mm in axial direction to one of the tips of the scanner head and for coarse positioning of the scanning area within the exposed facet,
Overview. This Policy sets forth the circumstances and procedures under which the Company shall recover Erroneously Awarded Compensation from current and former Executive Officers of the Company in accordance with rules issued by the United States Securities and Exchange Commission (the “SEC”) under the Securities Exchange Act of 1934 (the “Exchange Act”) and the Nasdaq Stock Market. Please refer to Section 3 below for definitions of capitalized terms used and not otherwise defined herein.