Ionosphere monitoring and inter-frequency bias determination using Galileo: First results and future prospects

We present first results of using the European Global Navigation Satellite System (GNSS) Galileo for determining the Total Electron Content (TEC). Furthermore, we describe a calibration technique which can be used to determine GNSS inter-frequency and inter-system biases along with calibrated TEC.     

The evolution of the central component in SN 1986J

The unusual core-collapse supernova 1986J, in the nearby spiral NGC 891, is the first modern supernova in which evidence of a compact remnant of the supernova has been seen. This evidence comes from recent VLBI images, which show the emergence of a new radio component in the center of the expanding radio shell. The new component shows an inverted radio spectrum contrasting with that of the shell. The new component is likely radio emission associated with the black-hole or neutron star compact remnant of the explosion, which would mark the first direct observational link between a modern supernova and such a compact remnant. We report here on our recent VLBI images at 22 and 5 GHz, as well as on our monitoring of the integrated radio spectrum of SN 1986J. In the 22 GHz image, the central component is marginally resolved.     

Nanosatellites and micro systems technology — capabilities, limitations and applications

In recent years Micro Systems Technology (MST) was introduced to manufacture miniaturized components for satellite subsystems, like small sensors, valves, micromotors, antennas and many more. These components can be used to build a new class of satellites weighing considerably less than 10 kg, with the capabilities comparable to present microsatellites. With the possibility of cheap mass production of such nanosatellites new applications become possible. However, the construction of very small satellites is connected with problems concerning launch, orbit control and, deorbiting. Furthermore the reduction of size creates certain limits for power consumption, data rates and optical resolutions which have to be carefully considered.     

On the conditions for fluidisation in cometary mantles

In our current understanding, active cometary nuclei comprise a volatile-depleted outer crust covering a mixture of dust and ices. During each perihelion passage the thermal wave penetrates the crust and sublimates a portion of these ices, which then escape the nucleus, dragging with them dust particles that replenish the coma and dust tail. The flux of released gases is likely to vary as a complex function of solar distance, nucleus structure, spin rate, etc. It has been previously hypothesised that at some point a fluidised state could occur, in which the gas drag is approximately equal to the weight of overlying dust and ice grains. This state is well understood and used in industrial processes where extensive mixing of the gas and solid components is desired. The literature on fluidisation under reduced gravity and pressure conditions is here reviewed and published relations used to predict the conditions under which fluidisation could occur in the near-surface of a cometary nucleus.     

X-38, CRV and CRV Evolution Program Overview and European Role

The X-38 Project forms part of the “X” prototype vehicle family developed by the United States. Its development was initiated by NASA to prepare the Crew Return Vehicle (CRV). The European participation in the X-38 Program has been significantly extended since the start of the X-38 cooperation in 1997 and is realized by ESA's “Applied Reentry Technology Program” and the German/DLR “Technologies for Future Space Transportation Systems” (TETRA) Project. European contributions to the X-38 Vehicle 201, (V-201) can be found in all technical key areas. The orbital flight and reentry with the X-38 V-201 will conclude the X-38 project in 2002.The CRV will be used from about mid-2005 as ’ambulance‘, ’lifeboat‘ or as alternate return vehicle for the crew of the International Space Station. Recognizing the very productive and mutually beneficial cooperation established on X-38, NASA and ESA have decided to continue this cooperation into the development of the operational CRV. The Phase C/D will be completed shortly after the Critical Design Review, scheduled for August 2002. The CRV production phase will start in October 2002 and will cover production of four CRV vehicles, ending in 2006.Based on the objective to identify a further evolution potential of the CRV towards a Crew Cargo Transfer Vehicle (CCTV), NASA has implemented upgrade studies in the CRV Phase C/D.     

Focal contacts organization in osteoblastic cells under microgravity and cyclic deformation conditions.

We compared quantitatively vinculin-related adhesion parameters in osteoblastic cells submitted to opposite mechanical stresses, i.e., low deformation and frequency strain regimens (stretch condition) and microgravity exposure (relaxed condition). Cyclic deformation induced a biphasic response comprising new focal contacts formation followed by their clustering in ROS cells. Microgravity exposure induced a reduction in focal contact number and clustering in ROS cells. We previously demonstrated that 1% cyclic deformations at 0.05 Hz during a daily 10 min episode over 7 days stimulated ROS 17/2.8 growth as compared to static culture whereas relaxed ROS proliferated similarly to static culture (BC). To evaluate whether the proliferation (stretch) or the survival (relaxed) status of ROS cells influences focal contact organization, we inhibited ERKs proliferative-dependent pathway. Inhibition of proliferation by PD98059 was overcome although not fully restored by stretch. Furthermore stretch-induced clustering of vinculin-positive contacts still occurs in the presence of ERKs inhibitor, whereas the increase in focal contact number is abolished. In conclusion, we showed that focal contacts are mechanoeffectors and that hyper-mechanical stimulation could up regulate focal contacts size as compared to hypo-mechanical that down regulate clusterization.     

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.     

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.