Continuous flow oxidation of HMF using supported AuPd-alloy

The oxidation of 5-(Hydroxymethyl)furfural (HMF) to 2,5-Furandicarboxylic acid (FDCA) holds significant promise for replacing fossil-based monomers. Continuous flow operation enhances the process in terms of green chemistry by improving heat and mass transfer, enabling easier scalability of the reaction and ensuring higher safety with a smaller reactor volume. In this study, we investigated the use of heterogeneous catalysts in a fixed-bed reactor for the continous oxidation of HMF. Air served as green oxidant, water as non-toxic solvent, and Na2CO3 as mild base. An AuPd-alloy-based catalyst supported on activated carbon demonstrated remarkable performance, yielding 81% FDCA at a liquid hourly space velocity of 31.4 h-1. This corresponds to a productivity of 68 molFDCA molM-1 h-1, which is, to our knowledge, one order of magnitude higher than typically reported for the heterogeneously catalyzed continuous oxidation of HMF. In addition, the catalyst showed a good stability over 90 h of time on stream without any detectable deactivation. The formation of humins led to a progressive catalyst deactivation. The developed catalytic system and continuous process offer a more sustainable and efficient approach to future production of the renewable monomer FDCA

Swarm accelerometer data processing from raw accelerations to thermospheric neutral densities

The Swarm satellites were launched on November 22, 2013, and carry accelerometers and GPS receivers as part of their scientific payload. The GPS receivers do not only provide the position and time for the magnetic field measurements, but are also used for determining non-gravitational forces like drag and radiation pressure acting on the spacecraft. The accelerometers measure these forces directly, at much finer resolution than the GPS receivers, from which thermospheric neutral densities can be derived. Unfortunately, the acceleration measurements suffer from a variety of disturbances, the most prominent being slow temperature-induced bias variations and sudden bias changes. In this paper, we describe the new, improved four-stage processing that is applied for transforming the disturbed acceleration measurements into scientifically valuable thermospheric neutral densities. In the first stage, the sudden bias changes in the acceleration measurements are manually removed using a dedicated software tool. The second stage is the calibration of the accelerometer measurements against the non-gravitational accelerations derived from the GPS receiver, which includes the correction for the slow temperature-induced bias variations. The identification of validity periods for calibration and correction parameters is part of the second stage. In the third stage, the calibrated and corrected accelerations are merged with the non-gravitational accelerations derived from the observations of the GPS receiver by a weighted average in the spectral domain, where the weights depend on the frequency. The fourth stage consists of transforming the corrected and calibrated accelerations into thermospheric neutral densities. We present the first results of the processing of Swarm C acceleration measurements from June 2014 to May 2015. We started with Swarm C because its acceleration measurements contain much less disturbances than those of Swarm A and have a higher signal-to-noise ratio than those of Swarm B. The latter is caused by the higher altitude of Swarm B as well as larger noise in the acceleration measurements of Swarm B. We show the results of each processing stage, highlight the difficulties encountered, and comment on the quality of the thermospheric neutral density data set.Astrodynamics & Space Mission

Laser-Entfernungsmessungen zu Erdsatelliten - oder: Wie viele Zentimeter sind es bis zum Mond

Seit seinem erstmaligen Einsatz 1964/65 hat sich das Verfahren der Laser-Entfernungsmessung durch ständige technologische Weiterentwicklung zur genauesten kosmisch-geodätischen Messmethode entwickelt. Distanzmessungen zu Laser- Reflektoren auf künstlichen Erdsatelliten und dem Mond haben eine breite Palette von Anwendungen gefunden, die von der exakten Bestimmung des Erdschwerefeldes über die zentimetergenaue Vermessung der Mondbahn bis hin zum Nachweis relativistischer Effekte reicht

Laser Ranging to Nano-SatellitesG. Kirchner (1), Ludwig Grunwaldt (2), Reinhard Neubert (2), Franz Koidl (1), Merlin Barschke (3), Zizung Yoon (3), Hauke Fiedler (4), Christine Hollenstein (5)

Several small satellites in the class of pico- and nano-satellites will be equipped with multiple small corner cubes: OPS-SAT (ESA), S-Net and TechnoSat (8 kg resp. 15 kg; Technical University Berlin), and CubETH (ETH Zuerich). The size of these satellites is in the range from 10x10x30 cm up to about 40x40x30 cm; the planned circular orbits are in the 450 – 620 km range. Commercially available 10 mm and 0.5” corner cubes will be used for SLR; a single corner cube of this size will be sufficient for SLR to the planned LEO orbits. Placing several of these corner cubes on each side of the satellites will not only allow for standard SLR and POD, but also for an independent attitude determination with < 1° accuracy, even after the end of the satellites lifetime, or in case of problems or satellite failure. For multiple satellites flying in close formation, it will be possible to distinguish the sequence of single satellites within the formation

Data efficiency for the satellite LARES

LARES, together with other laser ranged satellites and other space geodesy techniques are used by the scientific community to monitor global environmental changes including melting of the polar ice caps. The accuracy reached today with these sophisticated techniques is very high since they allow to monitor for instance the Earth rotation axis shifts with accuracies of a few millimeters or better. In the case of laser ranging, this accuracy depends on many factors, but the main one is the number of the data collected by the tracking network daily. This raw data set is reduced to a compressed set of laser returns, called normal points - NPs, for analysis. The paper is devoted to describing the quantity and quality of the satellite laser ranging (SLR) data acquired from the satellite LARES with respect to other similar satellites. This analysis is instrumental to understand the accuracy required in the field of Earth science and in particular of global environmental monitoring

First results from the GPS atmosphere sounding experiment TOR aboard the TerraSAR-X satellite

GPS radio occultation events observed between 24 July and 17 November 2008 bythe IGOR occultation receiver aboard the TerraSAR-X satellite are processed and ana-lyzed. The comparison of 16 262 refractivity profiles with collocated ECMWF data yielda mean bias of−0.60% to+0.02% at altitudes between 5 and 30 km. Standard deviations decrease from about 0.8% to 1.8% at 5 km to about 0.5% to 0.8% at about 10kmaltitude. At low latitudes mean biases and standard deviations are larger, in particular inthe lower troposphere. The results are consistent with 15 159 refractivity observationscollected during the same time period by the BlackJack receiver aboard GRACE-Aand processed by GFZ’s operational processing system. The main difference between the two occultation instruments is the implementation of open-loop signal tracking inthe IGOR (TerraSAR-X) receiver which improves the tropospheric penetration depthin terms of ray height by about 2km compared to the conventional closed-loop dataacquired by BlackJack (GRACE-A).ISSN:1680-7375ISSN:1680-736

Swarm accelerometer data processing from raw accelerations to thermospheric neutral densities 2. Aeronomy Swarm Science Results after two years in Space

The Swarm satellites were launched on November 22, 2013, and carry accelerometers and GPS receivers as part of their scientific payload. The GPS receivers do not only provide the position and time for the magnetic field measurements, but are also used for determining non-gravitational forces like drag and radiation pressure acting on the spacecraft. The accelerometers measure these forces directly, at much finer resolution than the GPS receivers, from which thermospheric neutral densities can be derived. Unfortunately, the acceleration measurements suffer from a variety of disturbances, the most prominent being slow temperature-induced bias variations and sudden bias changes. In this paper, we describe the new, improved four-stage processing that is applied for transforming the disturbed acceleration measurements into scientifically valuable thermospheric neutral densities. In the first stage, the sudden bias changes in the acceleration measurements are manually removed using a dedicated software tool. The second stage is the calibration of the accelerometer measurements against the non-gravitational accelerations derived from the GPS receiver, which includes the correction for the slow temperature-induced bias variations. The identification of validity periods for calibration and correction parameters is part of the second stage. In the third stage, the calibrated and corrected accelerations are merged with the non-gravitational accelerations derived from the observations of the GPS receiver by a weighted average in the spectral domain, where the weights depend on the frequency. The fourth stage consists of transforming the corrected and calibrated accelerations into thermospheric neutral densities. We present the first results of the processing of Swarm C acceleration measurements from June 2014 to May 2015. We started with Swarm C because its acceleration measurements contain much less disturbances than those of Swarm A and have a higher signal-to-noise ratio than those of Swarm B. The latter is caused by the higher altitude of Swarm B as well as larger noise in the acceleration measurements of Swarm B. We show the results of each processing stage, highlight the difficulties encountered, and comment on the quality of the thermospheric neutral density data set