SUMMARYIn this paper, we investigate the solution of bang-bang optimal control problems by shooting methods. We will show how modifying the performance index by a term depending on a small parameter e yields more regular controls and shooting functions. A continuation procedure on e will lead us to a good approximation of the initial solution. Then, a statistical interpretation of the method is given, providing us with a general framework for building new regular controls. Finally, two numerical examples are solved illustrating the interest of our method.

Barnes, D. et al, The ExoMars rover and Pasteur payload Phase A study: an approach to experimental astrobiology, International Journal of Astrobiology (2006), 5:3:221-241 Cambridge University Press RAE2008The Aurora programme is the European Space Agency programme of planetary exploration focused primarily on Mars. Although the long-term goals of Aurora are uncertain, the early phases of the Aurora programme are based on a number of robotic explorer missions ? the first of these is the ExoMars rover mission currently scheduled for launch in 2013 (originally 2011). The ExoMars rover ? developed during a Phase A study ? is a 240 kg Mars rover supporting a 40 kg payload (called Pasteur) of scientific instruments specifically designed for astrobiological prospecting to search for evidence of extant or extinct life. In other words, ExoMars represents a new approach to experimental astrobiology in which scientific instruments are robotically deployed at extraterrestrial environments of astrobiological interest. Presented is an outline of the design of the rover, its robotic technology, its instrument complement and aspects of the design decisions made. ExoMars represents a highly challenging mission, both programmatically and technologically. Some comparisons are made with the highly successful Mars Exploration Rovers, Spirit and Opportunity.Peer reviewe

The European Venus Explorer (EVE) mission was proposed to the European Space Agency in 2007, as an M-class mission under the Cosmic Vision Programme. Although it has not been chosen in the 2007 selection round for programmatic reasons, the EVE mission may serve as a useful reference point for future missions, so it is described here. It consists of one balloon platform floating at an altitude of 50-60 km, one descent probe provided by Russia, and an orbiter with a polar orbit which will relay data from the balloon and descent probe, and perform science observations. The balloon type preferred for scientific goals is one which oscillates in altitude through the cloud deck. To achieve this flight profile, the balloon envelope contains a phase change fluid, which results in a flight profile which oscillates in height. The nominal balloon lifetime is 7 days-enough for one full circumnavigation of the planet. The descent probe's fall through the atmosphere takes 60 min, followed by 30 min of operation on the surface. The key measurement objectives of EVE are: (1) in situ measurement from the balloon of noble gas abundances and stable isotope ratios, to study the record of the evolution of Venus; (2) in situ balloon-borne measurement of cloud particle and gas composition, and their spatial variation, to understand the complex cloud-level chemistry; (3) in situ measurements of environmental parameters and winds (from tracking of the balloon) for one rotation around the planet, to understand atmospheric dynamics and radiative balance in this crucial region. The portfolio of key measurements is complemented by the Russian descent probe, which enables the investigation of the deep atmosphere and surface.

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