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  • SPACE COMMUNICATIONS, SPACECRAFT COMMUNICATIONS, COMMAND AND TRACKING  (2)
  • United States  (2)
  • 1
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    Unknown
    American Association for the Advancement of Science (AAAS)
    Publication Date: 1991-06-28
    Description: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Hansen, B C -- Hansen, K D -- New York, N.Y. -- Science. 1991 Jun 28;252(5014):1768.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/2063189" target="_blank"〉PubMed〈/a〉
    Keywords: Records as Topic ; *Scientific Misconduct ; United States ; *United States Public Health Service
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 2
    Publication Date: 2016-01-20
    Description: Massive open online courses (MOOCs) are often characterized as remedies to educational disparities related to social class. Using data from 68 MOOCs offered by Harvard and MIT between 2012 and 2014, we found that course participants from the United States tended to live in more-affluent and better-educated neighborhoods than the average U.S. resident. Among those who did register for courses, students with greater socioeconomic resources were more likely to earn a certificate. Furthermore, these differences in MOOC access and completion were larger for adolescents and young adults, the traditional ages where people find on-ramps into science, technology, engineering, and mathematics (STEM) coursework and careers. Our findings raise concerns that MOOCs and similar approaches to online learning can exacerbate rather than reduce disparities in educational outcomes related to socioeconomic status.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Hansen, John D -- Reich, Justin -- New York, N.Y. -- Science. 2015 Dec 4;350(6265):1245-8. doi: 10.1126/science.aab3782. Epub 2015 Dec 3.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Harvard Graduate School of Education, Harvard University, Cambridge, MA 02138, USA. john_hansen@mail.harvard.edu. ; Office of Digital Learning, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/26785488" target="_blank"〉PubMed〈/a〉
    Keywords: Adolescent ; Adult ; Career Choice ; Certification/*methods ; Education, Distance/*methods ; Engineering/education ; Humans ; Internet ; Learning ; Mathematics/education ; *Online Systems ; Science/education ; *Social Class ; Students ; Technology/education ; United States ; Young Adult
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 3
    Publication Date: 2011-08-18
    Description: Imperfect carrier reference causes a degradation in detection performance in coherent communication systems. A measure of this degradation is the radio loss, which is the amount of increase in data signal to noise ratio (SNR) per bit required to achieve the same bit error rate when carrier reference is perfect. Performance analysis and numerical results are obtained for the Voyager high rate telemetry link with maximum likelihood convolutional decoding. The arraying of antennas provides not only improved performance due to an increase in effective antenna aperture, but also a decrease in radio loss with respect to a single antenna. This telemetry link performance improvement is a function of the carrier loop SNR and data bit error rate. When the carrier loop SNR's are low, it provides a significant improvement in the telemetry link performance since the decrease in radio loss with respect to a single station is substantial.
    Keywords: SPACE COMMUNICATIONS, SPACECRAFT COMMUNICATIONS, COMMAND AND TRACKING
    Type: The Telecommun. and Data Acquisition Rept.; p 128-135
    Format: text
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  • 4
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    Unknown
    In:  Other Sources
    Publication Date: 2019-07-13
    Description: The present analysis of the use of a 32-GHz (Ka-band) downlink for deep space communications notes significant benefits over current standard 8.4-GHz downlinks; the consequences of the 8-dB telemetry performance gain thus obtained is presently evaluated for the case of the Cassini and Mars Sample Return missions. This potential can only be realized, however, with upgradings of both the ground stations in the Deep Space Network and the spacecraft communications subsystem. Proposals are made for the use of a Ka-band beacon on the Mars observer spacecraft, as well as the demonstration of such a system aboard the CRAF.
    Keywords: SPACE COMMUNICATIONS, SPACECRAFT COMMUNICATIONS, COMMAND AND TRACKING
    Type: AAS PAPER 86-420 , Aerospace century XXI: Space flight technologies; Oct 26, 1986 - Oct 29, 1986; Boulder, CO; United States
    Format: text
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