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{
    "url": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/email/523JBV36IEI3ZQKADVC4DMLTLVRC4SSD/",
    "mailinglist": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/",
    "message_id": "[email protected]",
    "message_id_hash": "523JBV36IEI3ZQKADVC4DMLTLVRC4SSD",
    "thread": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/thread/YUKH4DQ77SUSHNVLE4ZNNW6R2PFZPWJD/",
    "sender": {
        "address": "zleffke (a) vt.edu",
        "mailman_id": "57a24afb1cf641f98121841e6753c12e",
        "emails": "https://mailman.amsat.org/hyperkitty/api/sender/57a24afb1cf641f98121841e6753c12e/emails/"
    },
    "sender_name": "Zach Leffke",
    "subject": "Re: [amsat-bb] FM signal on FO-29?",
    "date": "2015-11-09T21:20:01Z",
    "parent": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/email/BBHHEJIPQTZ4JXUVKRKAMQDMCOB7E6IU/",
    "children": [],
    "votes": {
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    },
    "content": "Hi Daniel,\n     Thanks for the info.  I'll look into it more when I get a free \nmoment.  And for the cubic thing, I just meant that it appears that the \ndoppler S-curve looks like a third order polynomial over the course of a \nfull pass.  After a quick google search, the first image at this link is \nwhat I mean (in this case envision time along the y axis and doppler \noffset along the x axis).\n\nhttp://www.biology.arizona.edu/biomath/tutorials/polynomial/graphingpolynomials.html\n\nBut I haven't looked into this fully yet, and it sounds like you might \nbe saying that its not that simple.  I was just looking into regression \nequations for the purposes of curve fitting from a number of discrete \ndoppler offset observations.  At a quick glance, the cubic polynomial \nseemed like the right 'shape' for the regression.\n\nI think what you might be warning about is that, in doing so, because \nthere are a large number of parameters that go into the generation of \nthe doppler (and its s-curve), that we might be losing necessary \nfidelity in the data by assuming a cubic polynomial? Honestly this all \nkind of new territory for me, so any and all advice is welcome.\n\nThanks again for the info, much appreciated.\n\n-Zach, KJ4QLP\n\nResearch Associate\nTed & Karyn Hume Center for National Security & Technology\nVirginia Polytechnic Institute & State University\nWork Phone: 540-231-4174\nCell Phone: 540-808-6305\n\nOn 11/9/2015 3:29 PM, Daniel Estévez wrote:\n> Dear Bob and Zach,\n>\n> This paper might be worth looking at:\n> http://www.dtic.mil/dtic/tr/fulltext/u2/409103.pdf\n>\n> As far as I know, it started the whole business of location by\n> measurement of Doppler shift.\n>\n> Apparently, according to the success of project Transit, it is possible to:\n>\n> a) Compute the TLEs of a satellite by using just a few minutes of the\n> Doppler curve of the beacon of a satellite, as received on a ground\n> station with known location.\n>\n> b) Compute the location of a ground station, by using just a few minutes\n> of the Doppler curve of the beacon of a satellite with known TLEs, as\n> received on said ground station.\n>\n> Of course, several variation on this are possible, such as the one which\n> is discussed here:\n>\n> Compute the location of a ground station by using the Doppler curve of\n> its transmissions during a pass, as received on a satellite with known TLEs.\n>\n> It seems that the key point in all this is that the Doopler curve\n> depends independently on all the parameters in question (so not a cubic\n> polynomial, which depends on fewer parameters).\n>\n> 73,\n>\n> Dani M0HXM/EA4GPZ.\n>\n> El 09/11/15 a las 17:59, Zach Leffke escribió:\n>> No worries, I thought on it a bit more and I think a cubic polynomial is\n>> the right fit.  I also found some python tools for regression\n>> calculations that I think will be useful for this.  Also, I think this\n>> is pretty similar to how the COSPAS/SARSAT system used to locate lost\n>> ships (EPIRBs) and downed Aircraft (ELTs) before the proliferation of\n>> GPS and its inclusion in the locator beacons.\n\n",
    "attachments": []
}