This article reviews the technique of verbal protocol analysis and gives a profile of its use within software engineering research over the last two decades. An overview is given of the procedures used in verbal protocol analysis, and commonly-found difficulties in the application of the technique by researchers are described. The article reports on published efforts to develop tools to automate the procedures. A review of the literature shows trends in the use of the verbal protocol analysis in software engineering research from the 1980s to the present. Recurring themes of its purpose within software engineering research are identified, including the comparison of the behaviours of subjects with differing levels of expertise and the identification of effective software comprehension strategies. Advances and problems with the development of a general-purpose encoding scheme for verbal protocol analysis appropriate to a range of domains within software engineering are described.
Planetary landers have, in the past, relied on physical means to protect the payload from the shock of impact on the surface [1]. These landers, starting their descent from orbit with their initial position only known to a few kilometres, were not required to land at a particular landing spot, but only to land safely.Today, much more knowledge, obtained from earlier landings and high-resolution orbiting instruments, is available about the surfaces of some planets than was available when previous landers were designed.Missions are becoming more demanding in terms of the accuracy of landing and significant effort is now focused on the design of surface relative navigation systems.Surface relative navigation requires a sensor that can pick out features or landmarks on the surface and use these to track the position of the spacecraft relative to the surface -passive and active vision-based navigation sensors are currently being developed.The testing of these sophisticated sensors, in particular the image processing parts, required the development of a realistic, large-scale test bed, representative of the real planet's surface. Physical modelling was not able to meet the needs of the sensor testing, so a virtual reality tool has been developed.PANGU (Planet and Asteroid Natural Scene Generation Utility) is a software tool for simulating and visualising the surface of various planetary bodies. It has been designed to support the development of planetary landers that use computer vision to navigate towards the surface and to avoid any obstacles near the landing site. PANGU can be used to generate an artificial surface representative of cratered planets and to provide images of the simulated planet. When given the position and orientation of a spacecraft above the planet's surface, PANGU responds by producing an image of the surface from that view point. Current research is extending the capabilities of PANGU so that Martian surfaces and asteroids can also be simulated. This paper describes the PANGU simulation tool in detail and provides example images of the simulated surface as seen from a descending planetary lander. Downloaded by 178.174.154.35 on June 21, 2016 | http://arc.aiaa.org |
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