22,186 research outputs found
Equity and Efficiency of Community College Appropriations: The Role of Local Financing
The study analyzes the equity of community college financing and demonstrates intrastate variations in appropriations to community colleges. The ratio of 90th to 10th percentile values ranges from 2.0 to 2.8 in half the states analyzed, levels which are considered high in comparison to K-12 finance inequities. In 10 states with high revenue disparities, the direction of revenue deviations is more often progressive in state-funded than in local-share states, suggesting the local role may undermine equity. Differences in economies of scale, geographic costs, and program costs are explored as factors determining funding disparities
Summary of the electromagnetic compatibility evaluation of the proposed satellite power system
The effects of the proposed solar power satellite (SPS) operations on electronic equipment and systems by fundamental, harmonic, and intermodulation component emissions from the orbital station; and the fundamental, harmonic, and structural intermodulation emissions from the rectenna site were evaluated. The coupling and affects interactions affecting a wide spectrum of electronic equipment are considered. The primary EMC tasking areas are each discussed separately
Using ACIS on the Chandra X-ray Observatory as a particle radiation monitor
The Advanced CCD Imaging Spectrometer (ACIS) is one of two focal-plane
instruments on the Chandra X-ray Observatory. During initial radiation-belt
passes, the exposed ACIS suffered significant radiation damage from trapped
soft protons scattering off the x-ray telescope's mirrors. The primary effect
of this damage was to increase the charge-transfer inefficiency (CTI) of the
ACIS 8 front-illuminated CCDs. Subsequently, the Chandra team implemented
procedures to remove the ACIS from the telescope's focus during high-radiation
events: planned protection during radiation-belt transits; autonomous
protection triggered by an on-board radiation monitor; and manual intervention
based upon assessment of space-weather conditions. However, as Chandra's
multilayer insulation ages, elevated temperatures have reduced the
effectiveness of the on-board radiation monitor for autonomous protection. Here
we investigate using the ACIS CCDs themselves as a radiation monitor. We
explore the 10-year database to evaluate the CCDs' response to particle
radiation and to compare this response with other radiation data and
environment models.Comment: 10 pages, 5 figures. To appear in Proc. SPIE vol. 773
Video Guidance, Landing, and Imaging system (VGLIS) for space missions
The feasibility of an autonomous video guidance system that is capable of observing a planetary surface during terminal descent and selecting the most acceptable landing site was demonstrated. The system was breadboarded and "flown" on a physical simulator consisting of a control panel and monitor, a dynamic simulator, and a PDP-9 computer. The breadboard VGLIS consisted of an image dissector camera and the appropriate processing logic. Results are reported
Video guidance, landing, and imaging systems
The adaptive potential of video guidance technology for earth orbital and interplanetary missions was explored. The application of video acquisition, pointing, tracking, and navigation technology was considered to three primary missions: planetary landing, earth resources satellite, and spacecraft rendezvous and docking. It was found that an imaging system can be mechanized to provide a spacecraft or satellite with a considerable amount of adaptability with respect to its environment. It also provides a level of autonomy essential to many future missions and enhances their data gathering ability. The feasibility of an autonomous video guidance system capable of observing a planetary surface during terminal descent and selecting the most acceptable landing site was successfully demonstrated in the laboratory. The techniques developed for acquisition, pointing, and tracking show promise for recognizing and tracking coastlines, rivers, and other constituents of interest. Routines were written and checked for rendezvous, docking, and station-keeping functions
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