Mission analysis and systems design of a near-term and far-term pole-sitter mission

This paper provides a detailed mission analysis and systems design of a near-term and far-term polesitter mission. The pole-sitter concept was previously introduced as a solution to the poor temporal resolution of polar observations from highly inclined, low Earth orbits and the poor high-latitude coverage from geostationary orbit. It considers a spacecraft that is continuously above either the north or south pole and, as such, can provide real-time, continuous and hemispherical coverage of the polar regions. Being on a non-Keplerian orbit, a continuous thrust is required to maintain the pole-sitter position. For this, two different propulsion strategies are proposed, which result in a near-term pole-sitter mission using solar electric propulsion (SEP) and a far-term pole-sitter mission where the SEP thruster is hybridized with a solar sail. For both propulsion strategies, minimum propellant pole-sitter orbits are designed. In order to maximize the spacecraft mass at the start of the operations phase of the mission, the transfer from Earth to the pole-sitter orbit is designed and optimized assuming either a Soyuz or an Ariane 5 launch. The maximized mass upon injection into the pole-sitter orbit is subsequently used in a detailed mass budget analysis that will allow for a trade-off between mission lifetime and payload mass capacity. Also, candidate payloads for a range of applications are investigated. Finally, transfers between north and south pole-sitter orbits are considered to overcome the limitations in observations due to the tilt of the Earth’s rotational axis that causes the poles to be alternately situated in darkness. It will be shown that in some cases these transfers allow for propellant savings, enabling a further extension of the pole-sitter mission

Novel mission concepts for polar coverage : An overview of recent developments and possible future applications

The paper provides a survey of novel mission concepts for continuous, hemispheric polar observation and direct-link polar telecommunications. It is well known that these services cannot be provided by traditional platforms: geostationary satellites do not cover high-latitude regions, while low- and medium-orbit Sun-synchronous spacecraft only cover a narrow swath of the Earth at each passage. Concepts that are proposed in the literature are described, including the pole-sitter concept (in which a spacecraft is stationary above the pole), spacecraft in artificial equilibrium points in the Sun-Earth system and non-Keplerian polar Molniya orbits. Additionally, novel displaced eight-shaped orbits at Lagrangian points are presented. For many of these concepts, a continuous acceleration is required and propulsion systems include solar electric propulsion, solar sail and a hybridisation of the two. Advantages and drawbacks of each mission concept are assessed, and a comparison in terms of high-latitude coverage and distance, spacecraft mass, payload and lifetime is presented. Finally, the paper will describe a number of potential applications enabled by these concepts, focusing on polar Earth observation and telecommunications

Integrating spacecraft and aircraft in Earth Observation System architectures

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2011.Cataloged from PDF version of thesis.Includes bibliographical references (p. 170-176).The Global Earth Observation System (GEOS) is the essential data gathering network that enables the advancement of Earth science. In recent years, efforts have been made to understand the major GEOS architectural tradeoffs. Several decision support tools have been developed, including the Campaign-level Science Traceability Matrix (CSTM). The CSTM is a framework designed to trace the benefit delivered by a campaign of Earth observing systems to relevant stakeholders. This thesis first presents the CSTM v 1.1, an enhanced version of the original CSTM, which updates the scientific understanding captured in the framework. This benefit tracing framework is applied to the set of satellite missions recommended by the National Research Council Earth Science Decadal Survey. To support campaign scheduling, this thesis presents and applies a multi-objective Genetic Algorithm (GA), built using the Matlab GA toolkit. The algorithm seeks to maximize "Data Value", minimize the effects of "Data Gaps", and accounts for cost, budget, and technology readiness. The results show that under the current conditions, gaps in important measurements will arise in the near future as currently operational NASA Earth observation missions age and their replacements continue to experience development issues. This result motivates a systematic rethinking of measurement gap mitigation strategies and the use of airborne observational platforms in the GEOS. The integration of aircraft into the GEOS is explored through three case studies. Three unique modes of operation for aircraft in Earth observation are presented and characterized. Based on the results of the case studies, a quantitative framework, called CSTM v2.0, is introduced. CSTM v2.0 uses a Rule-Based Expert System (RBES) that evaluates instruments at a level of fidelity that allows for comparison between aircraft and spacecraft. The GA campaign scheduling tool is used to understand the role of aircraft in the GEOS. The results of this analysis show that aircraft provide a short-term source of high value missions and are able to fill critical measurement gaps. This thesis recommends that aircraft be considered as operational platforms in future GEOS architectures, recognizing that autonomous systems promise significant benefits for Earth observation.by Brandon H. Suarez.S.M

Environmental analysis of the chemical release module

The environmental analysis of the Chemical Release Module (a free flying spacecraft deployed from the space shuttle to perform chemical release experiments) is reviewed. Considerations of possible effects of the injectants on human health, ionosphere, weather, ground based optical astronomical observations, and satellite operations are included. It is concluded that no deleterious environmental effects of widespread or long lasting nature are anticipated from chemical releases in the upper atmosphere of the type indicated for the program

COBE's search for structure in the Big Bang

The launch of Cosmic Background Explorer (COBE) and the definition of Earth Observing System (EOS) are two of the major events at NASA-Goddard. The three experiments contained in COBE (Differential Microwave Radiometer (DMR), Far Infrared Absolute Spectrophotometer (FIRAS), and Diffuse Infrared Background Experiment (DIRBE)) are very important in measuring the big bang. DMR measures the isotropy of the cosmic background (direction of the radiation). FIRAS looks at the spectrum over the whole sky, searching for deviations, and DIRBE operates in the infrared part of the spectrum gathering evidence of the earliest galaxy formation. By special techniques, the radiation coming from the solar system will be distinguished from that of extragalactic origin. Unique graphics will be used to represent the temperature of the emitting material. A cosmic event will be modeled of such importance that it will affect cosmological theory for generations to come. EOS will monitor changes in the Earth's geophysics during a whole solar color cycle

A comparative investigation on performance and which is the preferred methodology for spectrum management; geo-location spectrum database or spetrum sensing

A Research Report submitted to the Faculty of Engineering and the Built Environment, University of Witwatersrand, in the partial fulfilment of the requirements for the degree of Master of Science in Engineering Johannesburg, 2015.Due to the enormous demand for multimedia services which relies hugely on the availability of spectrum, service providers and technologist are devising a means or method which is able to fully satisfy these growing demands. The availability of spectrum to meet these demands has been a lingering issue for the past couple of years. Many would have it tagged as spectrum scarcity but really the main problem is not how scarce the spectrum is but how efficiently allocated to use is the spectrum. Once such inefficiency is tackled effectively, then we are a step closer in meeting the enormous demands for uninterrupted services. However, to do so, there are techniques or methodologies being developed to aid in the efficient management of spectrum. In this research project, two methodologies were considered and the efficiency of these methodologies in the areas of spectrum management. The Geo-location Spectrum Database (GLSD) which is the most adopted technique and the Cognitive radio spectrum sensing technique are currently the available techniques in place. The TV whitespaces (TVWS) was explored using both techniques and certain comparison based on performances; implementation, practicability, cost and flexibility were used as an evaluation parameter in arriving at a conclusion. After accessing both methodologies, conclusions were deduced on the preferred methodology and how its use would efficiently solve the issues encountered in spectrum managemen

Campaign-level science traceability for Earth observation system architecting

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2009.Includes bibliographical references (p. 143-144).The Earth Sciences Decadal Survey of 2007 presented a comprehensive vision for the evolution of space-based Earth Science resources. The practical development of the Decadal campaign, however, has highlighted four challenges to the original plan: the growth of expected costs and the reduction of program budget, the loss and changing status of the expected precursor missions, the opportunity afforded by international earth science efforts, and the increasing desire to operationalize key measurements of the earth. This thesis discusses how system architecting of the Decadal campaign can realistically reproduce the decision logic of the Decadal Survey, while accurately capturing the necessary constraints and value functions, and can form the basis for rational analysis of the effects of changing assumptions. This thesis presents a technique for tracing stakeholder value to campaign architecture decisions through a system of science traceability matrices. Using a framework based upon decomposition of value-related elements, the costs and benefits of the Decadal campaign are analyzed. This thesis refines a technique for the scheduling of space-based observation campaigns and provides insight and recommendations for the Earth Observation Program. The decision logic of the Decadal Survey is implemented through constraints and value functions, and an algorithm for scheduling is developed. Finally, this algorithm is used to examine the impacts of key changes that have occurred since the publishing of the Decadal Survey and provide recommendations for the development of the Earth Science Decadal Survey campaign.by Theodore K. Seher.S.M

Research reports: 1991 NASA/ASEE Summer Faculty Fellowship Program

The basic objectives of the programs, which are in the 28th year of operation nationally, are: (1) to further the professional knowledge of qualified engineering and science faculty members; (2) to stimulate an exchange of ideas between participants and NASA; (3) to enrich and refresh the research and teaching activities of the participants' institutions; and (4) to contribute to the research objectives of the NASA Centers. The faculty fellows spent 10 weeks at MSFC engaged in a research project compatible with their interests and background and worked in collaboration with a NASA/MSFC colleague. This is a compilation of their research reports for summer 1991