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    Re: Glonass goes dark
    From: Jackson McDonald
    Date: 2014 Apr 9, 14:53 +0000
    Well, I did some cursory research and answered my own question.   Global positioning satellites are not in geosynchronous orbit.  


    The Global Positioning System (GPS) is a constellation of about 24 artificial satellites. The GPS satellites are uniformly distributed in a total of six orbits such that there are four satellites per orbit. This number of satellites and spatial distribution of orbits insures that at least eight satellites can be simultaneously seen at any time from almost anywhere on Earth. The GPS satellites circle the Earth at an altitude of about 20,000 km (13,000 miles) and complete two full orbits every day. The GPS satellites are not in a geostationary orbit, but rise and set two times per day. Each satellite broadcasts radio waves towards Earth that contain information regarding its position and time. We can receive this information by using special receivers, called GPS receivers, which can detect and decode this information. By combining signals transmitted by several satellites and received simultaneously, a GPS receiver can calculate its position on the Earth (i.e., its latitude and longitude) with an accuracy of approximately 10 m. There are more sophisticated receivers that can be used to determine position with an accuracy of a few millimeters.


    So, I corrected my mistaken understanding of GPS and learned something new.  

    I still wonder, however, whether the corruption of the GLONASS ephemeris data was accidental or intentional.   


    From: jacksonmcdonald---.com
    To: navlist@fer3.com
    Subject: RE: [NavList] Glonass goes dark
    Date: Wed, 9 Apr 2014 02:38:58 +0000

    First, I was surprised by the following sentence in the article:  "According to another source, a GLONASS fix could not take effect until each satellite in turn passed back over control stations in the Northern Hemisphere to be reset, thus taking nearly 12 hours."
    At the risk of displaying my ignorance, I had assumed that GLONASS, GPS, and other global positioning satellites were in geo-synchronous orbits.  If so, they are fixed and don't pass over control stations at intervals.   I profess no expertise in this area and would welcome clarifications and corrections from other, more knowledgeable members of this group.
    Second, given the recent tensions in East-West relations over Ukraine, one could logically ask whether the ephemeris data was intentionally corrupted in order to render the GLONASS system dysfunctional.  
    Does the Russian military depend solely on GLONASS, or do they also use GPS?

    From: FrankReed{at}HistoricalAtlas.com
    To: jacksonmcdonald---.com
    Date: Tue, 8 Apr 2014 15:02:17 -0700
    Subject: [NavList] Glonass goes dark

    Last week the entire GLONASS system (Russian GPS equivalent) transmitted corrupt data for about 12 hours. Details with a quote from Richard Langley at the link above.
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