A lightning swept stroke model: A valuable tool to investigate the lightning strike to aircraft

In the context of lightning strike on the Dassault Falcon family of aircraft, the standard zoning of Falcon 50, 900 and 2000, inferred from FAA and EUROCAE WG31 documents [US Department of Transportation, Federal Aviation Administration, Advisory Circular AC 20-53A, 1985; US Department of Transportation, Federal Aviation Administration, Advisory Circular AC 20-53B, Draft, 1991; EUROCAE WG 31, Aircraft Lightning Zoning Standard, ED-91, 1998], has been presented. Zoning proves to be quite similar between the three types of aircraft. Thanks to the feed-back on lightning strikes to Falcon, lightning traces have been observed on the fuselage for different flight conditions and aircraft. Observations are compared with the zoning performed by Dassault. A physical model, developed by ONERA, was used to simulate the sweeping of lightning on the fuselage of a Falcon 900. The results are in good agreement with the lightning traces observed on the fuselages.     

Fate of prebiotic adenine

Equilibrium adsorption isotherm data for the purine base adenine has been obtained on several prebiotically relevant minerals by frontal analysis using water as a mobile phase. Adenine is far displaced toward adsorption on pyrite (FeS2), quartz (SiO2), and pyrrhotite (FeS), but somewhat less for magnetite (Fe3O4) and forsterite (Mg2SiO4). The prebiotic prevalence of these minerals would have allowed them to act as a sink for adenine; removal from the aqueous phase would confer protection from hydrolysis as well, establishing a nonequilibrium thermodynamic framework for increased adenine synthesis. Our results provide evidence that adsorption phenomena may have been critical for the primordial genetic architecture.     

System test results from the GNC experiments on the PRISMA in-orbit test bed

The PRISMA in-orbit test bed will demonstrate guidance, navigation, and control strategies for spacecraft formation flying and rendezvous. The project is funded by the Swedish National Space Board and the prime contractor is the Swedish Space Corporation. The project is further supported by the German Aerospace Center, the Technical University of Denmark, and the French Space Agency. PRISMA was launched on June 15, 2010 and after three weeks of operations, all on-board systems and units have passed an initial commissioning phase. Separation of the two PRISMA satellites from each other is expected by mid-August 2010.PRISMA consists of two spacecraft: MAIN and TARGET. The MAIN spacecraft has full orbit control capability while TARGET is attitude controlled only.The Swedish Space Corporation is responsible for three groups of guidance, navigation, and control experiments. These experiments include GPS- and vision-based formation flying during which the spacecraft will fly in passive as well as forced motion. The three experiments are: autonomous formation flying, proximity operations with final approach/recede maneuvers, and autonomous rendezvous. This paper presents system test results from two of these experiments as obtained with the flight-ready system. The system tests consist of a series of simulations performed on the flight model spacecraft with a large amount of hardware in the loop.     

Security implications of remote sensing

Major technical advances in remote sensing have developed sophisticated systems with both extensive military and civilian applications. Not only the USA and USSR, but a growing number of other countries such as China, France, India and Japan are actively engaged in remote-sensing R&D. This article reviews the capabilities of civilian satellite technologies and programmes of various nations, and examines the implications for national and international security. Many states are concerned about the commercial availability of data on their economic resources and national security-related activities. A particular problem is the possible misinterpretation of remotely-sensed data.     

High-resolution SAR imaging with angular diversity

We propose to use the APES (amplitude and phase estimation) approach for the spectral estimation of gapped data and synthetic aperture radar (SAR) imaging with angular diversity. A relaxation-based algorithm, referred to as GAPES (Gapped-data APES), is proposed, which includes estimating the spectrum via APES and filling in the gaps via a least squares (LS) fitting. For SAR imaging with angular diversity data fusion, we perform one-dimensional (1-D) windowed fast Fourier transforms (FFTs) in range, use the GAPES algorithm to interpolate the gaps in the aperture for each range, apply 1-D inverse FFTs (IFFTs) and dewindow in range, and finally apply the two-dimensional (2-D) APES algorithm to the interpolated matrix to obtain the 2-D SAR image. Numerical results are presented to demonstrate the effectiveness of the proposed algorithm     

Flight demonstration of formation flying capabilities for future missions (NEAT pathfinder)

PRISMA is a demonstration mission for formation-flying and on-orbit-servicing critical technologies that involves two spacecraft launched in low Earth orbit in June 2010 and still in operation. Funded by the Swedish National Space Board, PRISMA mission has been developed by OHB-Sweden (formerly Swedish Space Corporation) with important contributions from the German Aerospace Centre (DLR/GSOC), the French Space Agency (CNES), and the Technical University of Denmark (DTU). The paper focuses on the last CNES experiment achieved in September 2012 that was devoted to the preparation of future astrometry missions illustrated by the NEAT and µ-NEAT mission concepts. The experiment consisted of performing the type of formation maneuvers required to point the two-satellite axis to a celestial target and maintain it fixed during the observation period. Achieving inertial pointing for a LEO formation represented a new challenge given the numerous constraints from propellant usage to star tracker blinding. The paper presents the experiment objectives in relation with the NEAT/µ-NEAT mission concept, describes its main design features along with the guidance and control algorithms evolutions and discusses the results in terms of performances achieved during the two rehearsals.