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Abstract: The limited depth of focus of microscope optics precludes the observation of a three-dimensional surface in a single view. For an efficient operation of a planetary microscope observing a highly irregular surface, an autofocus algorithm must detect partially focused views and merge them into a completely focused image (extended depth of focus). In this paper we investigate the suitability of different algorithms for autonomous image focusing onboard a Mars lander. We show that all methods under study, except for the Variance method, produce reasonable results and that their performance depends (amongst other factors) on sample morphology. For reasons of simplicity and reduced computational requirements we favor Gradient and Roberts methods and present an efficient implementation thereof. [ABSTRACT FROM AUTHOR]

The microscope for the Beagle 2 lander, which was launched as part of the European Space Agency''s Mars Express mission on 2 June 2003, will provide images of the Martian surface at around 6 μm resolution. It will provide optical images of the surface of Mars at a resolution 5 times higher than any other experiment currently planned. The device has a working distance of 12 mm and uses a set of 12 light-emitting diodes which surround the aperture to illuminate the sample in four colours. The target is brought into focus using a stepper motor. This article describes the scientific objectives and the design of the microscope. It also discusses initial results from ground calibration exercises which were designed to validate the system and describes aspects of its operation. [Copyright &y& Elsevier]