Browsing by Subject "Constellation"

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Analytical approach to the design of optimal satellite constellations for space-based space situational awareness applications
(2011-12) Biria, Ashley Darius; Marchand, Belinda G.; Lightsey, E. Glenn
In recent years, the accumulation of space debris has become an increasingly pressing issue, and adequately monitoring it is a formidable task for designated ground-based sensors. Supplementing the capabilities of these ground-based networks with orbiting sensing platforms would dramatically enhance the ability of such systems to detect, track, identify, and characterize resident space objects -- the primary goals of modern space situational awareness (SSA). Space-based space situational awareness (SBSSA), then, is concerned with achieving the stated SSA goals through coordinated orbiting sensing platforms. To facilitate the design of satellite constellations that promote SSA goals, an optimization approach is selected, which inherently requires a pre-defined mathematical representation of a cost index or measure of merit. Such representations are often analytically available, but when considering optimal constellation design for SBSSA applications, a closed-form expression for the cost index is only available under certain assumptions. The present study focuses on a subset of cases that admit exact representations. In this case, geometrical arguments are employed to establish an analytical formulation for the coverage area provided as well as for the coverage multiplicity. These analytical results are essential in validating numerical approximations that are able to simulate more complex configurations.
Delphinus
(The University of Texas at Austin, 2010-06-30) The University of Texas a Austin; McDonald Observatory; Star Date
Numerical analysis and design of satellite constellations for above the horizon coverage
(2010-12) Takano, Andrew Takeshi; Marchand, Belinda G.; Fowler, Wallace T.
As near-Earth space becomes increasingly crowded with spacecraft and debris, the need for improved space situational awareness has become paramount. Contemporary ground-based systems are limited in the detection of very small or dim targets. In contrast, space-based systems, above most atmospheric interference, can achieve significant improvements in dim target detection by observing targets against a clutter-free space background, i.e. targets above the horizon (ATH). In this study, numerical methods for the evaluation of ATH coverage provided by constellations of satellites are developed. Analysis of ATH coverage volume is reduced to a planar analysis of cross-sectional coverage area in the orbit plane. The coverage model performs sequences of boolean operations between polygons representing cross-sections of satellite sensor coverage regions and regions of interest, returning the coverage area at the desired multiplicity. This methodology allows investigation of any coverage multiplicity for planar constellations of any size, and use of arbitrary sensor profiles and regions of interest. The implementation is applied to several constellation design problems demonstrating the utility of the numerical ATH coverage model in a constellation design process.
Space Shuttle Program (SSP) retirement and NASA transition to the Vision for Space Exploration (VSE)
(2009-08) Reyes, Carlos Joel; Duvic, Robert Conrad, 1947-; Ambler, Tony
On January 14, 2004, President George W. Bush announced the Vision for Space Exploration (VSE). The goals of the vision include developing a new generation launch capability while completing assembly of the International Space Station (ISS) and retiring the Space Shuttle by 2010. In support of this goal, the Space Shuttle Program (SSP) initiated evaluation of hardware, infrastructure, and workforce skill mix needed to continue Space Shuttle flights until the projected 2010 retirement. The SSP also studied how NASA will deploy personnel from, and use the facilities of, the SSP to ensure that the Space Shuttle operates safely through its final flight, and to ensure personnel and facilities from the SSP are effectively transitioned to NASA’s exploration programs. NASA funding, like other federal agencies, is affected by various factors including domestic and international political environments, current and emerging technologies available to meet agency goals, and sustainability and potential economic return of federal expenditures. In this paper I will present a retrospective analysis of federal budget allocations to NASA as a percentage of the Federal Budget from years 1958 to 2010 (adjusted to 1979 dollars). The classic method for calculating net present value (NPV) is not well suited for projecting potential value of future R&D technologies. A quantitative analysis of R&D technologies transferred to private industry will be presented, as well as a description of a method of evaluating their significance will discussed relative to current budgetary considerations will likely for past, current and upcoming funding cycles. The opportunity at hand for NASA’s transition from SSP to Constellation in support of the VSE initiative is to advocate their culture as R&D innovators and emphasize the future benefit of increased funding.