Design of a Programmable Star Tracker-Based Reference System For a Simulated Spacecraft

The main objective of this research effort is to achieve an accuracy level for the SimSat star tracker system comparable to what is reported in current literature by various star tracker manufacturers and researchers. Previous work has provided a spherical star dome that needs to be fully populated with light sources. Programmable organic light emitting diode (OLED) panels were chosen to populate the dome to allow high contrast ratios without backlighting and increase the number of star combinations able to be represented. Noise equivalent angles less than five arcseconds (1 delta ) are achieved about the boresight axis and less than half an arcsecond around the other axes. Absolute accuracy near the center of the star dome is tested to be less than 0.04 degree about each axis. Two different approaches to inertially cataloging the star eld are also investigated, externally referencing each panels coordinates using a coordinate measurement arm and utilizing the camera\u27s known position to catalog the panel\u27s location. The full population of the SimSat star dome and reprogrammable capability of the panels allows many future research endeavors related to star pattern recognition and attitude determination to be undertaken

Decentralized on-board planning and scheduling for crosslink-enabled Earth-observing constellations

Thesis: S.M., Massachusetts Institute of Technology, Department of Aeronautics and Astronautics, 2019Cataloged from PDF version of thesis.Includes bibliographical references (pages 151-156).Small satellites have improved in capability, nearing a future where high data-rate payloads and crosslinks can provide improved geospatial and temporal coverage, while at a fraction of the cost. Planning and scheduling for efficient bulk data routing with discrete crosslink windows in a dynamic network is a difficult combinatorial optimization problem [30]. As problem size grows, quickly solving the planning and scheduling problem involves implementing algorithms that can leverage parallelization. Decentralized algorithms are inherently parallelizable and can be implemented on-orbit by individual satellites. This thesis investigates a decentralized approach that builds upon the Coupled Constraints Consensus Based Bundle Algorithm (CCBBA) with enhancements to address maximum flow problems.Maximum flow problems occur when moving some resource from sources to sinks across a network, such as a satellite constellation observing targets (sources), moving data between satellites with crosslinks, and down-linking to ground stations (sinks). The CCBBA enhancements include task forking, task outflow coupling, and dynamic task creation based on satellite flow direction preferences. These enhancements increase the total data throughput and decrease required runtime. When implemented on each satellite, this decentralized auction-based approach, named Iterative-CCBBA for Maximum Flow problems (ICMF), provides the following benefits: 1) has robustness in convergence to differences in agent situational awareness, 2) decouples operations from ground station planning resources, and 3) provides an inherently parallelizable algorithm, if implemented on the ground instead of each satellite.ICMF is compared to a state of the art Centralized Global Planner (CGP) in six test cases, with two different inclinations and three different numbers of total satellites. Across all six unique use cases, ICMF has linear scaling in number of consensus rounds and, on average, runs in 94% less time than the CGP, with a 4% improvement in total data volume delivered. ICMF is an effective planner for satellite constellations that value total data throughput and runtime efficiency. The CGP performs better on median latency for observations and median average target age of information, performing better by 58% and 23%, respectively. Future work options for incorporating additional data routing information that could help close the latency and target age of information gap while still using a decentralized approach are presented.by Warren Grunwald.S.M.S.M. Massachusetts Institute of Technology, Department of Aeronautics and Astronautic

Validating Transcripts with Probes and Imaging Technology

High-throughput gene expression screens provide a quantitative picture of the average expression signature of biological samples. However, the analysis of spatial gene expression patterns with single-cell resolution requires quantitative in situ measurement techniques. Here we describe recent technological advances in RNA fluorescence in situ hybridization (FISH) techniques that facilitate detection of individual fluorescently labeled mRNA molecules of practically any endogenous gene. These methods, which are based on advances in probe design, imaging technology and image processing, enable the absolute measurement of transcript abundance in individual cells with single-molecule resolution.National Cancer Institute (U.S.). Physical Sciences-Oncology Center (U54CA143874)National Institutes of Health (U.S.) (Pioneer award 1DP1OD003936

Designing long-term policy: re-thinking transition management

Long-term policy is enjoying something of a come-back in connection with sustainable development. The current revival tries to avoid the pitfalls of an earlier generation of positivistic long-range planning and control approaches. Instead, this new generation of policy design emphasises reflexive governance concepts. These aim at inducing and navigating complex processes of socio-technical change by means of deliberation, probing and learning. A practical expression of this move that is attracting growing international attention amongst researchers and practitioners is the policy of ‘Transition Management’ (TM) in the Netherlands. This article takes stock of TM implementation experience to date and discusses the critical issues it raises for long-term policy design. The article provides a framework and synthesis for this Special Issue, which comprises articles that address a range of those issues in more depth. We highlight three critical issues: the politics of societal learning, contextual embedding of policy design and dynamics of the design process itself. This leads us to propose a view on policy design as a contested process of social innovation. Our conclusion considers implications for continued work on designing transition management in practice as well as the reflexive capacities of democratic politics