Moon Search Algorithms for NASA's Dawn Mission to Asteroid Vesta

A moon or natural satellite is a celestial body that orbits a planetary body such as a planet, dwarf planet, or an asteroid. Scientists seek understanding the origin and evolution of our solar system by studying moons of these bodies. Additionally, searches for satellites of planetary bodies can be important to protect the safety of a spacecraft as it approaches or orbits a planetary body. If a satellite of a celestial body is found, the mass of that body can also be calculated once its orbit is determined. Ensuring the Dawn spacecraft's safety on its mission to the asteroid Vesta primarily motivated the work of Dawn's Satellite Working Group (SWG) in summer of 2011. Dawn mission scientists and engineers utilized various computational tools and techniques for Vesta's satellite search. The objectives of this paper are to 1) introduce the natural satellite search problem, 2) present the computational challenges, approaches, and tools used when addressing this problem, and 3) describe applications of various image processing and computational algorithms for performing satellite searches to the electronic imaging and computer science community. Furthermore, we hope that this communication would enable Dawn mission scientists to improve their satellite search algorithms and tools and be better prepared for performing the same investigation in 2015, when the spacecraft is scheduled to approach and orbit the dwarf planet Ceres

International Space Station and Spacecraft Processing Directorate Kennedy Space Center

No abstract availabl

Discovering sub-micron ice particles across Dione' surface

Water ice is the most abundant component of Saturn’s mid-sized moons. However, these moons show an albedo asymmetry - their leading sides are bright while their trailing side exhibits dark terrains. Such differences arise from two surface alteration processes: (i) the bombardment of charged particles from the interplanetary medium and driven by Saturn’s magnetosphere on the trailing side, and (ii) the impact of E-ring water ice particles on the satellites’ leading side. As a result, the trailing hemisphere appears to be darker than the leading side. This effect is particularly evident on Dione's surface. A consequence of these surface alteration processes is the formation or the implantation of sub-micron sized ice particles.The presence of such particles influences and modifies the surfaces' spectrum because of Rayleigh scattering by the particles. In the near infrared range of the spectrum, the main sub-micron ice grains spectral indicators are: (i) asymmetry and (ii) long ward minimum shift of the absorption band at 2.02 μm (iii) a decrease in the ratio between the band depths at 1.50 and 2.02 μm (iv) a decrease in the height of the spectral peak at 2.6 μm (v) the suppression of the Fresnel reflection peak at 3.1 μm and (vi) the decrease of the reflection peak at 5 μm relative to those at 3.6 μm.We present results from our ongoing work mapping the variation of sub-micron ice grains spectral indicators across Dione' surface using Cassini-VIMS cubes acquired in the IR range (0.8-5.1 μm). To characterize the global variations of spectral indicators across Dione' surface, we divided it into a 1°x1° grid and then averaged the band depths and peak values inside each square cell.We will investigate if there exist a correspondence with water ice abundance variations by producing water ice' absorption band depths at 1.25, 1.52 and 2.02 μm, and with surface morphology by comparing the results with ISS color maps in the ultraviolet, visible and infrared ranges. Finally, we will compare the results with those obtained for Enceladus, Tethys, and Mimas

A new automated strategy for optimizing inclined interplanetary low-thrust trajectories

This study proposes a new automated strategy for designing and optimizing three-dimensional interplanetary low-thrust (LT) trajectories. The method formulates the design as a hybrid optimal control problem and solves it using a two-step approach. In Step 1, a three-dimensional model based on generalized logarithmic spirals is used with heuristics in combination with a gradient-based solver to perform an automated multi-objective global search of trajectories and optimize for parameters defining the spirals, the launch date, as well as the number, sequence and configuration of the planetary flybys. In Step 2, candidate solutions from Step 1 are refined by further optimization with a direct method. Results show that, compared to similar algorithms based on two-dimensional models, the strategy implemented in Step 1 leads to better estimates of the optimal trajectories, especially when the orbits of the involved bodies are inclined with respect to the ecliptic plane. The proposed approximate method (Step 1) yields better agreement with high-fidelity solutions (Step 2) in terms of launch, flyby and arrival dates, in-plane and out-of-plane average LT accelerations and propellant consumption, leading to improved convergence when the Step 1 trajectories are employed to initiate the search in Step 2

The Magellan Venus explorer's guide

The Magellan radar-mapping mission to the planet Venus is described. Scientific highlights include the history of U.S. and Soviet missions, as well as ground-based radar observations, that have provided the current knowledge about the surface of Venus. Descriptions of the major Venusian surface features include controversial theories about the origin of some of the features. The organization of the Magellan science investigators into discipline-related task groups for data-analysis purposes is presented. The design of the Magellan spacecraft and the ability of its radar sensor to conduct radar imaging, altimetry, and radiometry measurements are discussed. Other topics report on the May 1989 launch, the interplanetary cruise, the Venus orbit-insertion maneuver, and the in-orbit mapping strategy. The objectives of a possible extended mission emphasize the gravity experiment and explain why high-resolution gravity data cannot be acquired during the primary mission. A focus on the people of Magellan reveals how they fly the spacecraft and prepare for major mission events. Special items of interest associated with the Magellan mission are contained in windows interspersed throughout the text. Finally, short summaries describe the major objectives and schedules for several exciting space missions planned to take us into the 21st century

Methods and tools for preliminary low thrust mission analysis

The aim of the present thesis is to develop new methods that are useful for a space mission analyst to design low thrust trajectories in the preliminary phases of a mission study, where the focus is more on exploring various concepts than on obtaining one optimal transfer. The tools cover three main axes: generating low thrust trajectories from scratch, improving existing low thrust trajectories and exploring large search spaces related to multiple gravity assist transfers. Stress is put on the computational efficiency of the tools. Transfer arcs are generated with shaped based approaches, which have the advantage of having the ability to reproduce close to optimal transfers satisfying time of flight constraints and varied boundary constraints without the need for propagation. This thesis presents a general framework for the development of shape-based approaches to low-thrust trajectory design. A novel shaping method, based on a three-dimensional description of the trajectory in spherical coordinates, is developed within this general framework. Both the exponential sinusoid and the inverse polynomial shaping are demonstrated to be particular two-dimensional cases of the spherical one. The pseudo-equinoctial shaping is revisited within the new framework, and the nonosculating nature of the pseudo-equinoctial elements is analysed. A two-step approach is introduced to solve the time of flight constraint, related to the design of low-thrust arcs with boundary constraints for both spherical and pseudo-equinoctial shaping. The solutions derived from the shaping approach are improved with a feedback linear-quadratic controller and compared against a direct collocation method based on finite elements in time. Theoretical results are given on the validity of the method and a theorem is derived on the criteria of optimality of the results. The shaping approaches and the combination of shaping and linear-quadratic controller are tested on four case studies: a mission to Mars, a mission to asteroid 1989ML, to comet Tempel-1 and to Neptune. The design of low thrust multiple gravity assist trajectories is tackled by an incremental pruning approach. The incremental pruning of reduced search spaces is performed for decoupled pairs of transfer legs, after which regions of the total search space are identified where all acceptable pairs can be linked together. The gravity assists are not powered therefore the trajectory is purely low thrust and the transfer arcs are modelled by shaping functions and improved with the linear quadratic controller. Such an approach can reduce the computational burden of finding a global optimum. Numerical examples are presented for LTMGA transfers from Earth to asteroid Apollo and to Jupiter

Aeronautics and Space Report of the President: Fiscal Year 2007 Activities

The National Aeronautics and Space Act of 1958 directed the annual Aeronautics and Space Report to include a "comprehensive description of the programmed activities and the accomplishments of all agencies of the United States in the field of aeronautics and space activities during the preceding calendar year." In recent years, the reports have been prepared on a fiscal-year basis, consistent with the budgetary period now used in programs of the Federal Government. This year's report covers activities that took place from October 1, 2006, through September 30, 2007

IAU Symposium 160

Some of the topics considered include: Search Programs, Populations of Small Bodies, Dynamics, Physical Observations and Modeling, Observations from Space, Origin and Evolution, and Data Bases.Sponsored by International Astronomical Union.Organized by Osservatorio Astronomico di Torino and the Lunar and Planetary Institute.With the contribution of Regione Piemonte, Provincia di Novara, A.P.T. Lago Maggiore, Consiglio Nazionale delle Ricerche, European Space Agency, Alenia Spazio S.p.A.; with the participation of Banca Popolare di Novara, Camera di Commercio di Novara, Martini & Rossi IVLAS S.p.A.PARTIAL CONTENTS: SMACS: Small Missions to Asteroids and Comets. A Fast, Low Cost Approach to the Space Reconnaissance of Near-Earth Objects / M.J.S. Belton--Stochasticity of Comet P/GE-Wang / D. Benest and R. Gonczi--Chips Off of 4 Vesta: A Newly Confirmed Asteroid Family and Link to Basaltic Achondrite Meteorites / R.P. Binzel--Asteroid 243 IDA as a Member of the Koronis Family: Predictions and Implications for the Galileo Encounter / R.P. Binzel and S.M. Slivan--Photoelectric Observations of 4179 Toutatis / C. Blanco and D. Riccioli--Observations of OH in P/Swift-TuttIe and in Several Recent Weak Comets with the Nancay Radio Telescope / D. Bockehie-Morvan, G. Bourgois, P. Colom, J. Crovisier, E. Gerard, and L. Jorda--The Origin of the 3.2-3.6 Micron Emission Features in Comets: Gas or Dust / D. Bockelee-Morvan, T.Y. Brooke, and J. Crovisier--Observations of Sub-millimeter Lines of CH30H, HCN and H2CO in Comet P/Swift-Tuttle with the James Clerk Maxwell Telescope / D. Bockelee-Morvan, R. Padman, J.K. Davies, and J. Crovisier--Astrometric Measurements of Minor Planets in 1991-1992 / G. Bocsa and M. Birlan--Concerted Elemental Analyses- PIXE and TOF-SIMS- of Interplanetary Dust Particles / J. Bohsung, E.K. Jessberger, and T. Stephan--Dynamical Effects of Asymmetric Nongravitational Forces on Long-Period Comets / A. Bolalto, G. Carballo, and J.A. Fenuindez--Images of Comet Swift-Tuttle 1992t in the Light of H20+ and CO+ Ions, and Dust / T. Bonev, K. Jockers, and G.P. Chernova--Two Components in Meteor Spectra / J. Borovicka