Impact of instrument schedule growth on mission cost and schedule growth for recent NASA missions
This study explores instrument schedule delays and their impacts on mission development schedule and cost growth for recent NASA missions. This study examines 86 instruments across 32 NASA missions. First, the relationship between instrument schedule growth and mission development cost growth is examined. It is found that instrument development delays have a prominent role in contributing to mission development schedule and cost growth. Second, instrument developments are analyzed in order to explore specific trends related to schedule growth and to determine potential contributing factors. Instrument schedule growth is examined as a function of mass, power, instrument type, and spacecraft destination. The results are then used to establish schedule rules-of-thumb that can be used for planning purposes by project and program managers in charge of future NASA development efforts.
Using Historical NASA Cost and Schedule Growth to Set Future Program and Project Reserve Guidelines
By looking at historical schedule and cost growth, the past can be used to established reserve guidelines for future missions. This paper looks at recent NASA cost and schedule growth history, categorizes the reasons for growth, isolates growth due to external programmatic reasons versus internal technical reasons, assesses relationships for causality and provides guidance for the proper cost and schedule reserves to be carried at both the Program and Project levels. Mission cost and schedule growth history from both planetary and Earth-orbiting programs, such as Mars Exploration, Discovery, Medium and Small Explorer, Earth System Science Pathfinder, New Millennium and others, are investigated. The reserve guidelines developed are compared to industry standard guidelines and rules of thumb to determine if these standard practices continue to be valid.
Investigation of scatter radiation of non-circular X-ray scan trajectories
Modern interventional X-ray devices are highly maneuverable and allow complex 3D imaging trajectories. New scan trajectories enable not only optimized object sampling but also introduce new approaches for dynamic 3D imaging. In this paper, we investigated the scatter radiation of two different scan trajectories. The scatter radiation was sampled by a rail setup with dosimeters at defined positions. After data analysis, contour maps were generated which show for four exemplary heights the scatter radiation distribution. The alternative scan trajectory showed smaller dose exposures at heights correlated to upper torso and head areas of a model physician. Keywords—Image acquisition, alternative scan trajectory, circular tomosynthesis, scatter radiation distribution