Extended Pile Driving Model to Predict the Penetration of the Insight/HP<Superscript>3</Superscript> Mole into the Martian Soil

The NASA InSight mission will provide an opportunity for soil investigations using the penetration data of the heat flow probe built by the German Aerospace Center DLR. The Heat flow and Physical Properties Probe (HP³) will penetrate 3 to 5 meter into the Martian subsurface to investigate the planetary heat flow. The measurement of the penetration rate during the insertion of the HP³ will be used to determine the physical properties of the soil at the landing site. For this purpose, numerical simulations of the penetration process were performed to get a better understanding of the soil properties influencing the penetration performance of HP³. A pile driving model has been developed considering all masses of the hammering mechanism of HP³. By cumulative application of individual stroke cycles it is now able to describe the penetration of the Mole into the Martian soil as a function of time, assuming that the soil parameters of the material through which it penetrates are known. We are using calibrated materials similar to those expected to be encountered by the InSight/HP³ Mole when it will be operated on the surface of Mars after the landing of the InSight spacecraft. We consider various possible scenarios, among them a more or less homogeneous material down to a depth of 3–5 m as well as a layered ground, consisting of layers with different soil parameters. Finally we describe some experimental tests performed with the latest prototype of the InSight Mole at DLR Bremen and compare the measured penetration performance in sand with our modeling results. Furthermore, results from a 3D DEM simulation are presented to get a better understanding of the soil response.     

Lunar exploration and development--a sustainable model

A long-term goal of space exploration is the development of a lunar settlement that will not only be largely self-sufficient but also contribute to the economy of the Earth-Moon system. Proposals for lunar mining and materials processing developments, as well as tourism-based applications, have appeared in the literature for many years. However, so great are the technical and financial difficulties associated with sustained lunar development that, more than 30 years after the end of the Apollo programme, there have been no practical advances towards this goal. While this may soon be remedied by a series of proposed unmanned orbiters, landers and rovers, the philosophy of lunar exploration and development remains the same as it has for decades: conquer, exploit, and ignore the consequences. By contrasting the well-recognised problems of Earth orbital debris and the barely recognised issue of intentional spacecraft impacts on the lunar surface, this paper illustrates the need for a new model for lunar exploration and development. This new paradigm would assign a value to the lunar environment and provide a balance between protection and exploitation, creating, in effect, a philosophy of sustainable development for the Moon. It is suggested that this new philosophy should be an integral part of any future strategy for lunar colonisation.     

Remote sensing and the first amendment

The images and information available from remote-sensing satellites are potentially valuable to a large market. The news media is part of this market, ready to make major use of new near real-time information offered by the latest technology, which can provide images with resolution of less than 10 metres. A media business consortium (‘Mediasat’) could be created. However, the US Land Remote Sensing Commercialization Act of 1984 places tough licensing restrictions on any US company wanting to put a camera into orbit. The author argues that these restrictions clash with the US Constitutional right of freedom of information, and the press's right to gather information.     

Solar Ultraviolet Bursts

The term “ultraviolet (UV) burst” is introduced to describe small, intense, transient brightenings in ultraviolet images of solar active regions. We inventorize their properties and provide a definition based on image sequences in transition-region lines. Coronal signatures are rare, and most bursts are associated with small-scale, canceling opposite-polarity fields in the photosphere that occur in emerging flux regions, moving magnetic features in sunspot moats, and sunspot light bridges. We also compare UV bursts with similar transition-region phenomena found previously in solar ultraviolet spectrometry and with similar phenomena at optical wavelengths, in particular Ellerman bombs. Akin to the latter, UV bursts are probably small-scale magnetic reconnection events occurring in the low atmosphere, at photospheric and/or chromospheric heights. Their intense emission in lines with optically thin formation gives unique diagnostic opportunities for studying the physics of magnetic reconnection in the low solar atmosphere. This paper is a review report from an International Space Science Institute team that met in 2016–2017.     

Outer Plasmaspheric Plasma Properties: What We Know from Satellite Data

Our understanding of the composition, density, and temperature structure of the outer plasmasphere has undergone several major revisions since the discovery of the plasmasphere over 35 years ago. Each new era of understanding was brought about by the launching of satellites carrying suites of plasma diagnostic experiments each more sophisticated than its predecessor. Instead of each new generation of missions providing incremental advancement in our knowledge of the plasmasphere's plasma properties, they most often than not, initiated a complete re-thinking of our understanding. There are still a number of observational "puzzles" and large gaps in our knowledge of how plasmaspheric structure and plasma properties change with geomagnetic storm and substorm activity. As we develop new missions to attempt to globally image the outer plasmasphere in order to put simultaneous multi-spacecraft observations into context, we undoubtedly will uncover new tantalizing observations that will cause us to re-think our mental picture of the plasmasphere. What we have learned from satellite data about the chemical composition, density, temperature and pitch-angle distribution properties and their variability is outlined in this review paper.     

The Lunar Orbiter Laser Altimeter Investigation on the Lunar Reconnaissance Orbiter Mission

The Lunar Orbiter Laser Altimeter (LOLA) is an instrument on the payload of NASA’s Lunar Reconnaissance Orbiter spacecraft (LRO) (Chin et al., in Space Sci. Rev. 129:391–419, 2007). The instrument is designed to measure the shape of the Moon by measuring precisely the range from the spacecraft to the lunar surface, and incorporating precision orbit determination of LRO, referencing surface ranges to the Moon’s center of mass. LOLA has 5 beams and operates at 28 Hz, with a nominal accuracy of 10 cm. Its primary objective is to produce a global geodetic grid for the Moon to which all other observations can be precisely referenced.     

NanoSail-D: A solar sail demonstration mission

In the early to mid-2000s, NASA made substantial progress in the development of solar sail propulsion systems. Solar sail propulsion uses the solar radiation pressure exerted by the momentum transfer of reflected photons to generate a net force on a spacecraft. To date, solar sail propulsion systems were designed for large robotic spacecraft. Recently, however, NASA has been investigating the application of solar sails for small satellite propulsion. The NanoSail-D is a subscale solar sail system designed for possible small spacecraft applications. The NanoSail-D mission flew on board the ill-fated Falcon Rocket launched August 2, 2008, and due to the failure of that rocket, never achieved orbit. The NanoSail-D flight spare is ready for flight and a suitable launch arrangement is being actively pursued. This paper will present an introduction solar sail propulsion systems and an overview of the NanoSail-D spacecraft.     

Space ethics and protection of the space environment

The construction of the International Space Station in low Earth orbit and the formulation of plans to search for life on Mars indicate that mankind is intent on making the space environment part of its domain. Publicity surrounding space tourism, in-space ‘burials’ and the sale of lunar ‘real estate’ suggests that, some time in the 21st century, the space environment will become an extension of our current terrestrial business and domestic environment. This prompts the question of our collective attitude towards the space environment and the degree to which we should regulate its use and protect it for future generations. This article offers a pragmatic view of an ethical code for space exploration and development, as far as it relates to the protection of the space environment.