Mars Exploration Rovers Landing Dispersion Analysis

Landing dispersion estimates for the Mars Exploration Rover missions were key elements in the site targeting process and in the evaluation of landing risk. This paper addresses the process and results of the landing dispersion analyses performed for both Spirit and Opportunity. The several contributors to landing dispersions (navigation and atmospheric uncertainties, spacecraft modeling, winds, and margins) are discussed, as are the analysis tools used. JPL’s MarsLS program, a MATLAB-based landing dispersion visualization and statistical analysis tool, was used to calculate the probability of landing within hazardous areas. By convolving this with the probability of landing within flight system limits (in-spec landing) for each hazard area, a single overall measure of landing risk was calculated for each landing ellipse. In-spec probability contours were also generated, allowing a more synoptic view of site risks, illustrating the sensitivity to changes in landing location, and quantifying the possible consequences of anomalies such as incomplete maneuvers. Data and products required to support these analyses are described, including the landing footprints calculated by NASA Langley’s POST program and JPL’s AEPL program, cartographically registered base maps and hazard maps, and flight syste

Task and Institutional Influences on Managers' Mental Models of Competition

From institutional theory, we argue (a) that the competitive, or task environment may encourage divergence of management cognition between organizations, management functions and amongst senior managers, and (b) that the institutional environment may encourage cognitive convergence at the level of the industry, the strategic group and within institutionalized practices linked to management functions and level. Using management cognition of competition as a vehicle and two cognitive mapping methods, we test a series of competing propositions amongst 32 managers in the UK personal financial services industry, an industry that evidences both task and institutional characteristics. Our findings indicate neither the superiority of exclusively task nor institutional explanations of management cognition. However, the results do indicate some influence of the institutional environment, most noticeably through the convergence of mental models within middle managers across the industry. The results also indicate some influence of the task environment, through cognitive differences across organizations and greater differentiation amongst senior managers' mental models. We interpret our results by referring to the usefulness of distinguishing between task and institutional environments in management cognition and strategic management research