Description: No abstract is available for this article.

Description: We analyze and compare two approaches for the tomographic reconstruction of trace gas distributions in the atmosphere, adapted to Differential Optical Absorption Spectroscopy (DOAS) applications. The first approach performs the inversion by solving a regularized least-squares problem. Regularization is required because the retrieval of the distribution from a limited set of measurements is an ill posed problem. This approach does not consider the non-negativity of the trace gas concentrations. The second approach is a new proposal that solves an optimization problem with the Laplacian of the solution as the regularization term. This approach enables the possibility of adding the non-negativity constraint to the solution. The algorithm here is stated as an instance of a convex optimization problem and can numerically be solved using, for example, the CVX package. We test both approaches on reconstructions of simulated gas distributions and different experimental configurations applicable to Multi-Axis DOAS and multi-spectral imaging measurements. From the results, we can then determine a set of reconstruction parameters appropriate to real plume measurements.

Description: A data product has been generated and archived on the NASA Planetary Data System (Geosciences Node) which presents the seismometer readings of Viking Lander 2 in an easy-to-access form, for both the raw ('High rate') waveform records and the compressed ('Event mode') amplitude and frequency records. In addition to the records themselves, a separate summary file for each instrument mode lists key statistics of each record together with the meteorological measurements made closest in time to the seismic record. This juxtaposition facilitates correlation of the seismometer instrument response to different meteorological conditions, or the selection of seismic data during which wind disturbances can be expected to be small. We summarize data quality issues and also discuss lander-generated seismic signals, due to operation of the sampling arm or other systems, which may be of interest for prospective missions to other bodies. We review wind-seismic correlation, the 'Sol 80' candidate seismic event, and identify the seismic signature of a probable dust devil vortex on Sol 482 : the seismometer data allow an estimate of the peak wind, occurring between coarsely-spaced meteorology measurements. We present code to generate the plots in this paper to illustrate use of the data product.

Description: The AuroraWatch UK aurora alert service uses a network of magnetometers from across the United Kingdom to measure the disturbance in the earth's magnetic field caused by the aurora borealis (northern lights). The service has been measuring disturbances in the earth's magnetic field from the UK, and issuing auroral visibility alerts to its subscribers, since September 2000. These alerts have four levels, corresponding to the magnitude of disturbance measured, which indicate from where in the UK an auroral display might be seen. In the following, we describe the AuroraWatch UK system in detail and reprocess the historical magnetometer data using the current alert algorithm to compile an activity database. This data set is comprised of over 150,000 hours (99.94% data availability) of magnetic disturbance measurements, including nearly 9,000 hours of enhanced geomagnetic activity.

Description: The Mars Science Laboratory rover Curiosity, operating on the surface of Mars, is exposed to radiation fluxes from above and below. Galactic Cosmic Rays travel through the Martian atmosphere, producing a modified spectrum consisting of both primary and secondary particles at ground level. These particles produce an upward- directed secondary particle spectrum as they interact with the Martian soil. Here, we develop a method to distinguish the upward and downward directed particle fluxes in the RAD instrument, verify it using data taken during the cruise to Mars and apply it to data taken on the Martian surface.We use a combination of Geant4 and Planetocosmics modeling to find discrimination criteria for the flux directions. After developing models of the cruise phase and surface shielding conditions, we compare model- predicted values for the ratio of upward to downward flux with those found in RAD observation data.Given the quality of available information on MSL spacecraft and rover composition, we find generally reasonable agreement between our models and RAD observation data. This demonstrates the feasibility of the method developed and tested here. We additionally note that the method can also be used to extend the measurement range and capabilities of the RAD instrument to higher energies.

Description: No abstract is available for this article.

Description: In geodynamics as in other scientific areas, computation has become a core component of research, complementing field observation, laboratory analysis, experiment, and theory. Computational tools for data analysis, mapping, visualization, modeling, and simulation are essential for all aspects of the scientific workflow. Specialized scientific software is often developed by geodynamicists for their own use, and this effort represents a distinctive intellectual contribution. Drawing on a geodynamics community that focuses on developing and disseminating scientific software, we assess the current practices of software development and attribution, as well as attitudes about the need for and best practices for software citation. We analyzed publications by participants in the Computational Infrastructure for Geodynamics and conducted mix-method surveys of the solid earth geophysics community. From this we learned that coding skills are typically learned informally. Participants considered good code as trusted, reusable, readable and not overly complex and considered a good coder as one that participates in the community in an open and reasonable manor contributing to both long- and short-term community projects. Participants strongly supported citing software reflected by the high rate a software package was named in the literature and the high rate of citations in the references. However, lacking are clear instructions from developers on how to cite and education of users on what to cite. In addition, citations did not always lead to discoverability of the resource. A unique identifier to the software package itself, community education, and citation tools would contribute to better attribution practices.

Description: No abstract is available for this article.

Description: The TOPEX/Poseidon (T/P) altimetry mission operated for 13 years before the satellite was decommissioned in January 2006, becoming a large space debris object at an altitude of 1,340 km. Since the end of the mission, the interaction of T/P with the space environment has driven the satellite's spin dynamics. Satellite Laser Ranging (SLR) measurements collected from June 2014 until October 2016 allow for the satellite spin axis orientation to be determined with an accuracy of 1.7°. The spin axis coincides with the platform yaw axis (formerly pointing in the nadir direction) about which the body rotates in a counterclockwise direction. The combined photometric and SLR data collected over the 11-year time span indicates that T/P has continuously gained rotational energy at an average rate of 2.87 J/day and spins with a period of 10.73 s as of Oct. 19, 2016. The satellite attitude model shows a variation of the cross sectional area in the sun direction between 8.2 m 2 and 34 m 2 . The direct solar radiation pressure is the main factor responsible for the spin-up of the body and the exerted photon force varies from 65 μN to 228 μN around the mean value of 138.6 μN. Including realistic surface force modeling in orbit propagation algorithms will improve the prediction accuracy, giving better conjunction warnings for scenarios like the recent close approach reported by the ILRS Space Debris Study Group – an approximate 400 m flyby between T/P and Jason-2 on June 20, 2017 (ILRS, 2017).

Description: Data assimilation is carried out for the Martian atmosphere with the Mars Climate Sounder (MCS) retrievals of temperature, dust and ice. It is performed for the period Ls=180°to Ls=320°of Mars Year 29 with the Local Ensemble Transform Kalman Filter scheme and the Laboratoire de Météorologie Dynamique (LMD) Mars Global Climate Model (GCM). In order to deal with the forcings of aerosols (dust and water ice) on atmospheric temperatures, a framework is given for multivariate analysis. It consists of assimilating a GCM variable with the help of another GCM variable that can be more easily related to an observation. Despite encouraging results with this method, data assimilation is found to be intrinsically different for Mars, and more challenging, due to the Martian atmosphere being less chaotic and exhibiting more global features than on Earth. This is reflected in the three main issues met when achieving various data assimilation experiments: 1) temperature assimilation strongly forces the GCM away from its free-running state, due to the difficulty of assimilating global atmospheric thermal tides; 2) because of model bias, assimilation of airborne dust is not able to reproduce the vertical diurnal variations of dust observed by MCS, and not present in the GCM; 3) water ice clouds are nearly impossible to assimilate due to the difficulty to assimilate temperature to a sufficient precision. Overall, further improvements of Martian data assimilation would require an assimilation that goes beyond the local scale, and more realism of the GCM, especially for aerosols and thermal tides.