Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 1994. / Includes bibliographical references (p. 147-149). / by John Edward Robinson III. / M.S.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2012. / This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections. / Cataloged from student-submitted PDF version of thesis. / Includes bibliographical references (p. 103-105). / Air traffic is expected to continue to grow in the future and improved methods for dealing with the increased demand on the system need to be designed and implemented. One method for reducing surface congestion at airports is surface congestion management (SCM) (also commonly called departure queue management or departure metering). The concept generally involves holding aircraft at the gate or in the ramp area instead of releasing them onto the active movement area during periods of high departure demand. The FAA is planning to implement surface congestion management at airports where the cost/benefit analysis is favorable. Therefore, an estimate of the benefits of implementing surface congestion management in the future is necessary. To overcome the uncertainties and difficulties inherent in forecasting, this thesis adopts a multi-fidelity modeling approach and proposes three methods for estimating the benefits of SCM where the higher fidelity models study a subset of airports to inform and validate the lower fidelity models used on the entire set of airports. In the first model, a detailed analysis of a field trial of SCM at JFK airport is conducted using operational data. The second model estimates the benefits of implementing SCM at 8 major US airports from 2010 to 2030 by simulating congestion and performance levels through taxi time estimation. The last model explores several options for generalizing the results to 35 airports in the US. The results are also validated against historical benefits estimates as well as field trials of SCM where available. The findings show that SCM will result in fuel savings on the order of 1% of the total fuel burn in all stages of flight and between 5% and 45% of taxi-out fuel burn, depending on the airport. / by Alex Nakahara. / S.M.

Thesis: S.M., Massachusetts Institute of Technology, Department of Aeronautics and Astronautics, 2015. / Cataloged from PDF version of thesis. / Includes bibliographical references (pages 119-125). / We present and analyze the performance of two algorithms that plan and coordinate activities for a resource-constrained Earth-observing CubeSat constellation. The first algorithm is the Resource-Aware SmallSat Planner (RASP), which performs low-level planning of observation and communication activities for a single satellite while simultaneously keeping the satellite's onboard resources within specified bounds. RASP utilizes a Mixed Integer Linear Program based formulation and Depth First Search for construction of consistent onboard activity timelines. The second algorithm is the Limited Communication Constellation Coordinator (LCCC), which performs high level coordination of observations across the constellation through a distributed, "weak" consensus mechanism. The performance of the algorithms is tested with a 24 hour simulation of an eighteen satellite constellation over multiple orbital geometries and inter-satellite communication contexts. The orbital geometries include a modified Walker Star constellation and an "ad hoc" constellation defined by historical launches of CubeSats. The multiple communication contexts simulate different methods for sharing observation planning information between the satellites, and include sharing through inter-satellite crosslinks, downlink and uplink to ground stations, connection to a commercial communications constellation, and no sharing at all. Five analyses of the algorithms' performance were conducted, including average revisit times achieved, the numbers of communications links executed, how effectively planning information was shared, the resource margins maintained by the satellites, and the average execution time for the planner. Information sharing significantly aided in balancing revisit times across multiple Earth regions and three sensor choices, reducing the disparity in average revisit times between sensors from 514 minutes to 10 minutes for the Walker case and 617 to 11 minutes for he Ad Hoc case. Significantly more crosslink opportunities were available on average for the Walker satellites than for Ad Hoc (89.2 versus 47.7) and more crosslinks were executed for the Walker case (30.3 versus 20.8). Crosslink was found to be less effective than downlink at sharing planning information across the constellation, with a lower average latency (186 minutes versus 434, Walker) and better average initial timeliness (-35 minutes versus -287, Walker). Information sharing through both a commercial constellation and downlink outperformed sharing through just downlink or just crosslink, with an average latency and initial timeliness of 77 and 74 minutes (Walker). Average data storage and energy storage margins were kept high, as desired, for both constellations, at around 85 and 70 %. RASP planning time was found to scale roughly with the square of planning window length, but stays under a minute in all cases tested (achieving a maximum of 37.71 seconds). / by Andrew Kitrell Kennedy. / S.M.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 1995. / Includes bibliographical references (p. 117-119). / by Amy Jean McCain. / M.S.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2007. / Includes bibliographical references (p. 151-156). / This thesis develops a mission planning and scheduling algorithm that enables a single Unmanned Undersea Vehicle (UUV) to concurrently perform high level activities, while managing various resources in a dynamic ocean environment. Such activities may include wide area surveillance of a specified region and focused inspection tasks. Concurrent execution of activities allows a UUV to perform portions of different activities that share overlapping regions consecutively to increase vehicle productivity. Resources considered in this algorithm range from concrete quantities, such as the remaining battery energy, to variables representing operational restrictions, such as the maximum allowable navigation uncertainty. The first step in the development defines a parameterization that describes each high level activity in terms of smaller atomic tasks. In order to determine a sequence/path of tasks for the UUV to perform, a Prize Winning Salesman Problem with Replenishment Arcs (PW-RATSP) formulation transforms the set of atomic tasks into a set of nodes representing sequences of non-resource-replenishment tasks and a set of arcs that represent sequences of resource-replenishment tasks. The algorithm then expresses and solves the PWRATSP formulation as a mixed integer linear program (MILP). Finally, the algorithm employs a receding horizon approach to improve MILP computational performance and account for unexpected events and changes to the environment. Simulation results for test cases combining surveillance and inspection activities, and multiple resource replenishment activities show that the PW-RATSP UUV mission planning algorithm provides the ability to manage concurrent activities, perform temporal reasoning, and account for a mix of replenishable and non-replenishable vehicle resources. / by Larry Chang. / S.M.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 1996. / Includes bibliographical references (p. 95-97). / by John Matthew Kerwin. / M.S.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 1989. / Includes bibliographical references (leaves 130-132). / by Patrick Hanley. / Ph.D.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2007. / Includes bibliographical references (p. 63-65). / Astronauts perform space teleoperation tasks with visual feedback from outside cameras. Individuals differ greatly in the ability to integrate camera views, understand the workspace, and ensure clearances between the robot arm and obstacles. We believe that these individual differences correlate with two known subcomponents of spatial intelligence: perspective-taking (PT) and spatial visualization (SV). A preliminary study [1] supports this hypothesis. We believe astronauts use PT (the ability to imagine an object from a different viewpoint) to integrate camera information into an environmentally-referenced frame defined by the arm control axes. In some cases, it may be easier to visualize the manipulation of the payload with respect to the robot arm itself, than to the environment. In that case, SV(i.e., the ability to mentally manipulate an object from an egocentric perspective) may be exploited. We measured the performance of 25 naive subjects who used hand-controllers to rotate and translate, and 3 environmentally-fixed camera views. These devices controlled a 2-boom, 6 degree-of-freedom virtually-simulated arm to perform pickup and docking subtasks. / (cont.) To challenge the subjects' spatial ability we introduced a wide separation between camera views for some tests, and misalignments between the translation control and the display reference frames. We used the Perspective-Taking Ability test (PTA) and the Purdue Spatial Visualizations Test: Visualization of Views (PSVT:V) to measure PT, and the Cube Comparisons test (CC) to assess SV. We concluded that PTA predicted performance on pickup and docking subtasks, but PSVT:V did not. CC scores correlated with those measures of performance that did not necessarily require PT. High perspective-taking scorers performed the pickup task significantly more efficiently than low, but not faster. In docking, however, they were both significantly faster and more accurate, collided less often, and docked more accurately. In both tasks they moved along only one axis at a time. High CC scorers docked significantly more accurately and rotated about fewer axes at any one time. Whenever we found a significant effect of PSVT:V on a dependent variable, we also found one for PTA; but not the reverse. / (cont.) We had expected higher PT scorers to perform better than others under the challenge of wider camera angles and greater control-display frame misalignments, but we could not demonstrate this. On average females were slower and had lower docking accuracy, an effect related, perhaps, to their lower spatial ability scores. This study of performance during the first two hours of teleoperation training may help define issues for future research. / by María Alejandra Menchaca Brandan. / S.M.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2002. / Includes bibliographical references (p. 90-91). / by Geoffroy Lenglin. / S.M.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2013. / This thesis was scanned as part of an electronic thesis pilot project. / Cataloged from PDF version of thesis. / Includes bibliographical references (p. 181-187). / After centuries of studying the eight planets in our solar system, recent improvements in technology have given us the unprecedented opportunity to detect planets orbiting stars other than the sun, so-called exoplanets. Recent statistical studies based on 800 confirmed planets and more than 3000 planet candidates suggest that our galaxy is teeming with billions of planets. Many of them are likely to orbit their host stars at a distance where liquid water and potentially life can exist. Spectroscopic observations of exoplanets can provide us with information about the atmospheres and conditions on these distant worlds. This thesis presents a Bayesian retrieval framework to analyze spectroscopic observations of exoplanets to infer the planet's atmospheric compositions, the surface pressures, and the presences of clouds or hazes. I identify what can unambiguously be determined about the atmospheres of exoplanets by applying the retrieval method to sets of synthetic observations. The main finding is that a unique constraint of the atmospheric mixing ratios of all infrared absorbing gases and up to two spectrally inactive gases is possible if the spectral coverage of the observations is sufficient to (1) determine the broadband transit depths in at least one absorption feature for each absorbing gas and (2) measure the slope and strength of the molecular Rayleigh scattering signature. For the newly discovered class of low-density super-Earths, with radii and masses intermediate between Earth and Neptune, I present an observational approach to distinguish whether these planets more closely resemble the giant planets in our solar system or whether they represent a completely new, potentially water vapor-rich type of planet. The approach discussed in this work represents the science case for the largest Hubble Space Telescope program ever awarded for a single exoplanet. The numerical methods and the conceptual understanding of atmospheric spectra presented in this thesis are key for the design of future space telescopes dedicated to the characterization of transiting exoplanets. I present an integrated design evaluation framework for the proposed Exoplanet Characterization Observatory (EChO) that simultaneously models the astrophysical signal and the telescope's payload module. I demonstrate that costly cryogenic cooling to observe the mid-infrared spectrum beyond ~ 11 [mu]m is not required while visible light observations down to - 400 nm are essential for the mission success. The observational study of exoplanet atmospheres is in its infancy and its pace is poised to accelerate as observational techniques are improved and dedicated space missions are designed. The methods developed in this thesis will contribute to constraining the atmospheric properties of a wide variety of planets ranging from blazingly-hot gas giants to temperate Earth-like planets. / by Björn Benneke. / Ph.D.