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This study shows the potential risk of microfiltration between two different types of implant-abutment connections screwed at 45 Ncm: external and internal. For the first time the use of a mechanical artificial mouth is used with the values (compression and torsion loads with a frequency of 2 Hz) of the human chewing. The mechanical tests were performed with an artificial saliva at 37 oC. The microgap in the connection was measured by an Image Analysis software incorporated in a high resolution scanning electron microscopy. Implant connections were filled with methylene blue by using self-adjustable precision pipettes and the quantity of leakage was determined by high sensitivity spectometry. We showed that the internal connection has lower microgaps compared to the external ones and these microgaps increased with the number of mechanical cycles. The leakage of methylene blue was higher when the external connection was performed. Microgaps and the influence of the mechanical loads are very important for the long-term behavior avoiding the bacteria colonization in the dental implants. These aspects should be known by the implantologists.

<p>The Copernicus Sentinel-1 SAR (Synthetic Aperture Radar) mission consists of two satellites A and B launched in April 2014 and April 2016, respectively. The Copernicus POD (Precise Orbit Determination) Service is responsible for the generation of precise orbital products of the mission requiring a high orbit accuracy of 5 cm in 3D RMS in the comparison to external processing facilities.</p><p>The operational POD setup at the Copernicus POD Service has passed through several updates during the last years. For instance the ITRF update from ITRF08 to ITRF14 at the end of January 2017, the fundamental background model update in May 2020, and the switch to updated GPS antenna reference point coordinates together with the introduction of carrier phase ambiguity fixing at the end of July 2020 have been done to mention just the major changes in the processing. To provide a homogeneous and up-to-date orbit time series for the two satellites a reprocessing of the full mission period is done.  </p><p>The quality control of the reprocessed Copernicus Sentinel-1 orbits is done by analysing processing metrics and by comparing the results to orbits, which were independently reprocessed by members of the Copernicus POD Quality Working Group (QWG).</p><p>Results from the full Copernicus Sentinel-1 POD reprocessing campaign are presented together with the accuracy and quality assessment of the orbits.</p>

<p>The European Copernicus Sentinel-3 mission, a jointly operated mission by ESA and EUMETSAT, consists of two satellites equipped with GPS and DORIS receivers, and a Laser Retro Reflector (LRR) array, which allows tracking the satellites by Satellite Laser Ranging (SLR). The SLR observations are mainly used for the validation of GPS- and/or DORIS-derived precise orbit solutions. The SLR residuals are derived from the simple difference between observed and computed range between SLR station and the satellite. Only a subset of the SLR stations tracking the satellites is normally used for this purpose. The subset consists of stations delivering good quality observations on a long-term. The station selection is regularly reviewed to guarantee a continuous quality for the orbit validation.</p><p>Instead of using only a subset of the stations it would be preferable to use as many laser tracking data as possible. Long-term and highly accurate orbit time series of low Earth orbiting satellites can be used to estimate station range biases. The SLR validation is significantly improved by adding these station range biases due to additional stations and due to the removal of SLR related systematic patterns.</p><p>In the Copernicus POD Service (CPOD), the SLR station range biases are estimated based on a combined Sentinel-3A and -3B orbits computed from different orbit providers (the CPOD Quality Working Group). Performance, quality, mission dependency and stability of these SLR station range biases are analysed based on operational CPOD orbits and orbit solutions delivered by the Copernicus POD Quality Working Group.</p>

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The paper analyzes the problem of achieving a coherent operation in Geostationary SAR (GEOSAR) missions intended for continuous monitoring of land surfaces. In contrast to LEOSAR missions, GEOSAR uses very long SAR integration times (from minutes to hours). Accordingly phase errors due to orbit perturbations, radar master oscillator drift, atmosphere propagation and other sources must be conveniently compensated during SAR processing to avoid image defocusing. A network of Active Radar Calibrators (ARC) distributed on the observed scene is proposed, providing echo envelope and phase observations before Synthetic Aperture Processing. In this way the radar antenna phase center trajectory and other phase error sources can be continuously tracked and compensated using a pyramidal sub-aperture processing approach.Peer ReviewedPostprint (published version