A systematic approach to nonlinear rotorcraft model identification

The development of a powerful parameter estimation routine and its integration into the simulation environment HOST is described. With this tool approaches are being made towards new strategies of mathematical modeling, aimed at providing highly accurate and nevertheless run-time efficient simulation models. The identification routine is capable of optimizing parameterized models in both dynamic time domain simulation and static (e.g. trim state variation) conditions. Examples of both cases are presented to emphasize the improvement in the system response prediction and to demonstrate the abilities of the identification techniques in combination with the nonlinear simulation platform. This article reviews the activities and achievements accomplished by the DLR Institute of Flight Research and the ONERA Systems Control and Flight Dynamics Department during the last few years in the research on rotorcraft flight dynamics modeling and model identification. Future activities that require extensive high fidelity modeling are in the scope of the current and coming modeling activities that include the use of the presented methods and software technologies.     

Laser measurements to space debris from Graz SLR station

In order to test laser ranging possibilities to space debris objects, the Satellite Laser Ranging (SLR) Station Graz installed a frequency doubled Nd:YAG pulse laser with a 1 kHz repetition rate, a pulse width of 10 ns, and a pulse energy of 25 mJ at 532 nm (on loan from German Aerospace Center Stuttgart – DLR). We developed and built low-noise single-photon detection units to enable laser ranging to targets with inaccurate orbit predictions, and adapted our standard SLR software to include a few hundred space debris targets. With this configuration, we successfully tracked – within 13 early-evening sessions of each about 1.5 h – 85 passes of 43 different space debris targets, in distances between 600 km and up to more than 2500 km, with radar cross sections from >15 m² down to <0.3 m², and measured their distances with an average precision of about 0.7 m RMS.     

Planetary Protection and the astrobiological exploration of Mars: Proactive steps in moving forward

Future efforts towards Mars exploration should include a discussion about the effects that the strict application of Planetary Protection policies is having on the astrobiological exploration of Mars, which is resulting in a continued delay in the search for Martian life. As proactive steps in the path forward, here we propose advances in three areas. First, we suggest that a redefinition of Planetary Protection and Special Regions is required for the case of Mars. Particularly, we propose a definition for special places on Mars that we can get to in the next 10–20?years with rovers and landers, where try to address questions regarding whether there is present-day near-surface life on Mars or not, and crucially doing so before the arrival of manned missions. We propose to call those special places “Astrobiology Priority Exploration” regions (APEX regions). Second, we stress the need for the development of robotic tools for the characterization of complex organic compounds as unequivocal signs of life, and particularly new generations of complex organic chemistry and biosignature detection instruments, including advances in DNA sequencing. And third, we advocate for a change from the present generation of SUV-sized landers and rovers to new robotic assets that are much easier to decontaminate such as microlanders: they would be very small with limited sensing capabilities, but there would be many of them available for launch and coordination from an orbiting platform. Implementing these changes will help to move forward with an exploration approach that is much less risky to the potential Mars biosphere, while also being much more scientifically rigorous about the exploration of the “life on Mars” question – a question that needs to be answered both for astrobiological discovery and for learning more definitive lessons on Planetary Protection.     

The earth explorer candidates: Nine focused missions, all satellite classes

The size of a satellite should follow naturally from the mission requirements taking into account implementation constraints, notably the choice of launcher and programmatics. The key concepts are “focused mission” and “maximum return for the investment”. The nine candidates proposed for the ESA Earth Explorer programme of research missions form a good representative set to illustrate a discussion of satellite classes. These focused missions lead to satellites from less than 100 kg and 100 W, to more than 2000 kg and 2 kW of power generation and include flights of opportunity and precursor experiments.     

Möglichkeiten und grenzen von mikrowellensystemen zur fernerkundung von satelliten

(Possibilities and Limitations of Microwave Systems for Satellite Remote Sensing)—Microwaves are applied in satellite remote sensing in both active, i.e. radar systems and in passive, i.e. microwave radiometer systems. The advantages and disadvantages of active and passive microwave systems in comparison to each other and to optical systems are discussed shortly. It becomes evident that radar has advantages over microwave radiometry due to its ranging and velocity-measurement capability, due to its SAR-capability with its extremely fine resolution and due to the fact that no major theoretical limitations exist for the obtainable measurement accuracy.The most important radar systems for Earth and ocean observations from satellites are altimeter, scatterometer and imaging radars with real or synthetic aperture. The physical and technical basics of these types of radar are presented together with some applications. Examples for remote sensing data and results obtained from different microwave remote sensing systems show the present state of the art and the present possibilities and limitations of microwave systems for satellite remote sensing.     

Laser time transfer and its application in the Galileo programme

We are presenting the new instrument, new technology available and new measurement technique proposal for the Galileo programme – optical detector for the laser time transfer and one way laser ranging ground to space.     

Do we know the cosmic-ray boosters?

The literature on cosmic-ray acceleration tends to favour strong shocks (in supernovae, stellar and galactic winds) over compact boosters. Difficulties are posed by the spectrum which does not reveal the implied upper cutoff (at E = 10^13±1 eV), by the energy-dependent anisotropy at the high-energy end (at E 10¹⁸ eV), the missing hydrogen, the large required boosting efficiency, the high positron abundance at E 10 GeV, detailed studies of supernova shells, and by an inadequacy of the Sedov-Taylor model for supernova explosions. Solar and solar-wind data support single-step or few-step accelerations because of the large observed anisotropies and short time scales.

The importance of spindown in compact binary systems is often underestimated. Several neutron-star binaries have been detected at cosmic γ-ray energies. Cosmic-ray escape from the Galaxy may proceed supersonically through narrow tubes rather than via convective diffusion.     

High resolution spectro-polarimetry with a large balloon-borne solar telescope

The balloon mission “Sunrise” consists of a 1m lightweight solar telescope equipped with a powerful spectro-graph-polarimeter and a multi-channel filtergraph for the visible and the UV. The science goals of Sunrise are focussed on, but not limited to, the investigation of the solar surface magnetism. The key questions include the generation and maintenance of the variable magnetic field, the structure and dynamics of the chromosphere, and the interaction of material flow and magnetic field in sunspots.