Evaluating the Wind-Induced Mechanical Noise on the InSight Seismometers

The SEIS (Seismic Experiment for Interior Structures) instrument onboard the InSight mission to Mars is the critical instrument for determining the interior structure of Mars, the current level of tectonic activity and the meteorite flux. Meeting the performance requirements of the SEIS instrument is vital to successfully achieve these mission objectives. Here we analyse in-situ wind measurements from previous Mars space missions to understand the wind environment that we are likely to encounter on Mars, and then we use an elastic ground deformation model to evaluate the mechanical noise contributions on the SEIS instrument due to the interaction between the Martian winds and the InSight lander. Lander mechanical noise maps that will be used to select the best deployment site for SEIS once the InSight lander arrives on Mars are also presented. We find the lander mechanical noise may be a detectable signal on the InSight seismometers. However, for the baseline SEIS deployment position, the noise is expected to be below the total noise requirement \(>97~\%\) of the time and is, therefore, not expected to endanger the InSight mission objectives.     

The Theory of Gamma-Ray Bursts

This chapter gives a brief review on the theory of gamma-ray bursts (GRBs), including the models of multi-messengers (e.g., prompt multiwavelength electromagnetic emissions, high-energy neutrinos, ultra-high-energy cosmic rays, and gravitational waves) and central engines (in particular, mergers of binary neutron stars for short GRBs). For detailed reviews, please see (Piran in Phys. Rep. 314:575, 1999; Rev. Mod. Phys. 76:1143, 2004; Mészáros in Annu. Rev. Astron. Astrophys. 40:137, 2002; Rep. Prog. Phys. 69:2259, 2006; Zhang and Mészáros in Int. J. Mod. Phys. A 19:2385, 2004; Zhang in Chin. J. Astron. Astrophys. 7:1, 2007; Nakar in Phys. Rep. 442:166, 2007; Kumar and Zhang in Phys. Rep. 561:1, 2015).     

The effect of inlet conditions on the flow and heat transfer in multiple rotating cavity with axial throughflow

This paper discusses experimental results from two different build configurations of a heated multiple rotating cavity test rig.Measurements of heat transfer from the discs and tangential velocities are presented.The test rig is a 70% full scale version of a high pressure compressor stack of an axial gas turbine engine.Of particular interest are the internal cylindrical cavities formed by adjacent discs and the interaction of these with a central axial throughflow of cooling air.Tests were carried out for a range of non-dimensional parameters representative of high pressure compressor internal air system flows(Re up to 5×106 and Rez up to 2×105).Two different builds have been tested.The most significant difference between these two build configurations is the size of the annular gap between the(non-rotating) drive shaft and the bores of the discs.The heat transfer data were obtained from thermocouple measurements of surface temperature and a conduction solution method.The velocity measurements were made using a two component,LDA system.The heat transfer results from the discs show differences between the two builds.This is attributed to the wider annular gap allowing more of the throughflow to penetrate into the cavity.There are also significant differences between the radial distributions of tangential velocity in the two builds of the test rig.For the narrow annular gap,there is an increase of non-dimensional tangential velocity V/Ωr with radial location to solid body rotation V/Ωr=1.For the wider annular gap,the non-dimensional velocities show a decrease with radial location to solid body rotation.      

Paths not taken – The Gossamer roadmap’s other options

Highly efficient low-thrust propulsion is increasingly applied beyond commercial use, also in mainstream and flagship science missions, in combination with gravity assist propulsion. Another recent development is the growth of small spacecraft solutions, not in size but in numbers and individual capabilities.Just over ten years ago, the DLR-ESTEC Gossamer Roadmap to Solar Sailing was set up to guide technology developments towards a propellant-less and highly efficient class of spacecraft for solar system exploration and applications missions: small spacecraft solar sails designed for carefree handling and equipped with carried application modules.Soon, in three dedicated Gossamer Roadmap Science Working Groups it initiated studies of missions uniquely feasible with solar sails such as Displaced L₁ (DL1) space weather advance warning and monitoring, Solar Polar Orbiter (SPO) delivery to very high inclination heliocentric orbit, and multiple Near-Earth Asteroid (NEA) rendezvous (MNR). Together, they demonstrate the capability of near-term solar sails to achieve at least in the inner solar system almost any kind of heliocentric orbit within 10 years, from the Earth-co-orbital to the extremely inclined, eccentric and even retrograde. Noted as part of the MNR study, sail-propelled head-on retrograde kinetic impactors (RKI) go to this extreme to achieve the highest possible specific kinetic energy for the deflection of hazardous asteroids.At DLR, the experience gained in the development of deployable membrane structures leading up to the successful ground deployment test of a (20 m)², i.e., 20 m by 20 m square solar sail at DLR Cologne in 1999 was revitalized and directed towards a 3-step small spacecraft development line from as-soon-as-possible sail deployment demonstration (Gossamer-1) via in-flight evaluation of sail attitude control actuators (Gossamer-2) to an envisaged proving-the-principle flight in the Earth-Moon system (Gossamer-3). First, it turned the concept of solar sail deployment on its head by introducing four separable Boom Sail Deployment Units (BSDU) to be discarded after deployment, enabling lightweight 3-axis stabilized sailcraft. By 2015, this effort culminated in the ground-qualified technology of the DLR Gossamer-1 deployment demonstrator Engineering Qualification Model (EQM). For mission types using separable payloads, such as SPO, MNR and RKI, design concepts can be derived from the BSDU characteristic of DLR Gossamer solar sail technology which share elements with the separation systems of asteroid nanolanders like MASCOT. These nano-spacecraft are an ideal match for solar sails in micro-spacecraft format whose launch configurations are compatible with ESPA and ASAP secondary payload platforms.Like any roadmap, this one contained much more than the planned route from departure to destination and the much shorter distance actually travelled. It is full of lanes, narrow and wide, detours and shortcuts, options and decision branches. Some became the path taken on which we previously reported. More were explored along the originally planned path or as new sidings in search of better options when circumstance changed and the project had to take another turn. But none were dead ends, they just faced the inevitable changes when roadmaps face realities and they were no longer part of the road ahead. To us, they were valuable lessons learned or options up our sleeves. But for future sailors they may be on their road ahead.     

Transforming Dust to Planets

We review recent progress in understanding how nebular dust and gas are converted into the planets of the present-day solar system, focusing particularly on the “Grand Tack” and pebble accretion scenarios. The Grand Tack can explain the observed division of the solar system into two different isotopic “flavours”, which are found in both differentiated and undifferentiated meteorites. The isotopic chronology inferred for the development of these two “flavours” is consistent with expectations of gas-giant growth and nebular gas loss timescales. The Grand Tack naturally makes a small Mars and a depleted, dynamically-excited and compositionally mixed asteroid belt (as observed); it builds both Mars and the Earth rapidly, which is consistent with the isotopically-inferred growth timescale of the former, but not the latter. Pebble accretion can explain the rapid required growth of Jupiter and Saturn, and the number of Kuiper Belt binaries, but requires specific assumptions to explain the relatively protracted growth timescale of Earth. Pure pebble accretion cannot explain the mixing observed in the asteroid belt, the fast proto-Earth spin rate, or the tilt of Uranus. No current observation requires pebble accretion to have operated in the inner solar system, but the thermal and compositional consequences of pebble accretion have yet to be explored in detail.     

Neutrinos from Supernovae

Neutrinos are fundamental particles in the collapse of massive stars. Because of their weakly interacting nature, neutrinos can travel undisturbed through the stellar core and be direct probes of the still uncertain and fascinating supernova mechanism. Intriguing recent developments on the role of neutrinos during the stellar collapse are reviewed, as well as our current understanding of the flavor conversions in the stellar envelope. The detection perspectives of the next burst and of the diffuse supernova background will be also outlined. High-energy neutrinos in the GeV-PeV range can follow the MeV neutrino emission. Various scenarios concerning the production of high-energy neutrinos are discussed.     

Recent Advancements and Motivations of Simulated Pluto Experiments

This review of Pluto laboratory research presents some of the recent advancements and motivations in our understanding enabled by experimental simulations, the need for experiments to facilitate models, and predictions for future laboratory work. The spacecraft New Horizons at Pluto has given a large amount of scientific data already rising to preliminary results, spanning from the geology to the atmosphere. Different ice mixtures have now been detected, with the main components being nitrogen, methane, and carbon monoxide. Varying geology and atmospheric hazes, however, gives us several questions that need to be addressed to further our understanding. Our review summarizes the complexity of Pluto, the motivations and importance of laboratory simulations critical to understanding the low temperature and pressure environments of icy bodies such as Pluto, and the variability of instrumentation, challenges for research, and how simulations and modeling are complimentary.     

Research on High-Precision Measurement Systems of Modern Aircraft

High-precision measurement systems of modern aircraft are studied in this paper. A measurement system with correction in the structure of inertial navigation system is introduced for highprecision aircraft. In the correction algorithms, a linear error model of the navigation system is usually used. With the aim of increasing the accuracy of the navigation system, we propose a nonlinear correction algorithm based on the state dependent coefficient representation of the nonlinear model.     

Impact of Distance Determinations on Galactic Structure. II. Old Tracers

Here we review the efforts of a number of recent results that use old tracers to understand the build up of the Galaxy. Details that lead directly to using these old tracers to measure distances are discussed. We concentrate on the following: (1) the structure and evolution of the Galactic bulge and inner Galaxy constrained from the dynamics of individual stars residing therein; (2) the spatial structure of the old Galactic bulge through photometric observations of RR Lyrae-type stars; (3) the three-dimensional structure, stellar density, mass, chemical composition, and age of the Milky Way bulge as traced by its old stellar populations; (4) an overview of RR Lyrae stars known in the ultra-faint dwarfs and their relation to the Galactic halo; and (5) different approaches for estimating absolute and relative cluster ages.