Faster conception of radically innovative systems: the strategic and organizational challenge for space agencies

Are space agencies able to reform the way they are organized? Attempts to reduce the time it takes to conceive new systems and adapt project management while fostering innovation have so far shown mixed results. In this paper, we describe some of the intellectual, strategic and organizational challenges the agencies are about to face in the coming years: managing the ever growing complexity of space systems; defining a knowledge-based strategy as the basis of a renewed organization; and assuming a central role in the innovation process in relation to industry. This thesis is illustrated with a case study of the CNES Microsatellite Myriade program.     

Pioneer 10 Doppler data analysis: Disentangling periodic and secular anomalies

This paper reports the results of an analysis of the Doppler tracking data of Pioneer probes which did show an anomalous behaviour. A software has been developed for the sake of performing a data analysis as independent as possible from that of Anderson et al. [Anderson, J., Laing, P.A., Lau, E.L., Liu, A.S., Nieto, M.M., Turyshev, S.G. Study of the anomalous acceleration of Pioneer 10 and 11. Phys. Rev. D 65, 082004, 2002], using the same data set. A first output of this new analysis is a confirmation of the existence of a secular anomaly with an amplitude about 0.8 nm s⁻² compatible with that reported by Anderson et al. A second output is the study of periodic variations of the anomaly, which we characterize as functions of the azimuthal angle φ$\phi$ defined by the directions Sun–Earth Antenna and Sun-Pioneer. An improved fit is obtained with periodic variations written as the sum of a secular acceleration and two sinusoids of the angles φ$\phi$ and 2φ$2\phi$. The tests which have been performed for assessing the robustness of these results are presented.     

Meteors do not break exogenous organic molecules into high yields of diatomics

Meteoroids that dominate the Earth's extraterrestrial mass influx (50-300 microm size range) may have contributed a unique blend of exogenous organic molecules at the time of the origin of life. Such meteoroids are so large that most of their mass is ablated in the Earth's atmosphere. In the process, organic molecules are decomposed and chemically altered to molecules differently from those delivered to the Earth's surface by smaller (<50 microm) micrometeorites and larger (>10 cm) meteorites. The question addressed here is whether the organic matter in these meteoroids is fully decomposed into atoms or diatomic compounds during ablation. If not, then the ablation products made available for prebiotic organic chemistry, and perhaps early biology, might have retained some memory of their astrophysical nature. To test this hypothesis we searched for CN emission in meteor spectra in an airborne experiment during the 2001 Leonid meteor storm. We found that the meteor's light-emitting air plasma, which included products of meteor ablation, contained less than 1 CN molecule for every 30 meteoric iron atoms. This contrasts sharply with the nitrogen/iron ratio of 1:1.2 in the solid matter of comet 1P/Halley. Unless the nitrogen content or the abundance of complex organic matter in the Leonid parent body, comet 55P/Tempel-Tuttle, differs from that in comet 1P/Halley, it appears that very little of that organic nitrogen decomposes into CN molecules during meteor ablation in the rarefied flow conditions that characterize the atmospheric entry of meteoroids approximately 50 microm-10 cm in size. We propose that the organics of such meteoroids survive instead as larger compounds.     

Electrostatic accelerometer with bias rejection for gravitation and Solar System physics

Radio tracking of interplanetary probes is an important tool for navigation purposes as well as for testing the laws of physics or exploring planetary environments. The addition of an accelerometer on board a spacecraft provides orbit determination specialists and physicists with an additional observable of great interest: it measures the value of the non-gravitational acceleration acting on the spacecraft, i.e. the departure of the probe from geodesic motion.     

Search for the OH (X(2)Pi) Meinel band emission in meteors as a tracer of mineral water in comets: detection of N(2)(+) (A-X)

We report the discovery of the N(2)(+) A-X Meinel band in the 780-840 nm meteor emission from two Leonid meteoroids that were ejected less than 1000 years ago by comet 55P/Tempel-Tuttle. Our analysis indicates that the N(2)(+) molecule is at least an order of magnitude less abundant than expected, possibly as a result of charge transfer reactions with meteoric metal atoms. This new band was found while searching for rovibrational transitions in the X(2)Pi electronic ground state of OH (the OH Meinel band), a potential tracer of water bound to minerals in cometary matter. The electronic A-X transition of OH has been identified in other Leonid meteors. We did not detect this OH Meinel band, which implies that the excited A state is not populated by thermal excitation but by a mechanism that directly produces OH in low vibrational levels of the excited A(2)Sigma state. Ultraviolet dissociation of atmospheric or meteoric water vapor is such a mechanism, as is the possible combustion of meteoric organics.     

Venus Interior Structure and Dynamics

No two rocky bodies offer a better laboratory for exploring the conditions controlling interior dynamics than Venus and Earth. Their similarities in size, density, distance from the sun, and young surfaces would suggest comparable interior dynamics. Although the two planets exhibit some of the same processes, Venus lacks Earth’s dominant process for losing heat and cycling volatiles between the interior and the surface and atmosphere: plate tectonics. One commonality is the size and number of mantle plume features which are inferred to be active today and arise at the core mantle boundary. Such mantle plumes require heat loss from the core, yet Venus lacks a measurable interior dynamo. There is evidence for plume-induced subduction on Venus, but no apparent mosaic of moving plates. Absent plate tectonics, one essential question for interior dynamics is how did Venus obtain its young resurfacing age? Via catastrophic or equilibrium processes? Related questions are how does it lose heat via past periods of plate tectonics, has it always had a stagnant lid, or might it have an entirely different mode of heat loss? Although there has been no mission dedicated to surface and interior processes since the Magellan mission in 1990, near infrared surface emissivity data that provides information on the iron content of the surface mineralogy was obtained fortuitously from Venus Express. These data imply both the presence of continental-like crust, and thus formation in the presence of water, and recent volcanism at mantle hotspots. In addition, the study of interior dynamics for both Earth and exoplanets has led to new insights on the conditions required to initiate subduction and develop plate tectonics, including the possible role of high temperature lithosphere, and a renewed drive to reveal why Venus and Earth differ. Here we review current data that constrains the interior dynamics of Venus, new insights into its interior dynamics, and the data needed to resolve key questions.     

Implications of Rotation, Orbital States, Energy Sources, and Heat Transport for Internal Processes in Icy Satellites

Internal processes in icy satellites, e.g. the exchange of material from the subsurface to the surface or processes leading to volcanism and resurfacing events, are a consequence of the amount of energy available in the satellites’ interiors. The latter is mainly determined shortly after accretion by the amount of radioactive isotopes incorporated in the silicates during the accretion process. However, for satellites—as opposed to single objects—important contributions to the energy budget on long time-scales can come from the interaction with other satellites (forcing of eccentricities of satellites in resonance) and consequently from the tidal interaction with the primary planet. Tidal evolution involves both changes of the rotation state—usually leading to the 1:1 spin orbit coupling—and long-term variations of the satellite orbits. Both processes are dissipative and thus connected with heat production in the interior. The way heat is transported from the interior to the surface (convection, conduction, (cryo-) volcanism) is a second main aspect that determines how internal processes in satellites work. In this chapter we will discuss the physics of heat production and heat transport as well as the rotational and orbital states of satellites. The relevance of the different heat sources for the moons in the outer solar system are compared and discussed.     

Performance prediction and flowfield analysis of rotors in hover, using a coupled Euler/boundary layer method

The performance prediction of helicopter in hover is of key importance for manufacturers because hover is a design configuration for the definition of a rotorcraft. A lot of effort has been made for more than 10 years all over the world in order to develop and validate numerical methods based on CFD. An Euler method (WAVES) developed by ONERA and coupled with a boundary layer code (MI3DI) is presented, validated and applied to compute the total performance of rotors with different tip shapes. A new boundary condition for the Euler code has been tested and enables better calculation by eliminating ‘numerical' recirculation. The code has demonstrated its ability to rank two rotors with different planforms in good agreement with experiment. Under industrial requirements new grid strategies have been studied and should allow to reduce CPU time consumption. It is shown that WAVES/MI3DI can be efficiently used in the aerodynamic design process of a new rotor.