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{
    "url": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/email/HYEGBPBZDV23MXA4PR4TXAXFABRDQCFM/",
    "mailinglist": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/",
    "message_id": "[email protected]",
    "message_id_hash": "HYEGBPBZDV23MXA4PR4TXAXFABRDQCFM",
    "thread": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/thread/HYEGBPBZDV23MXA4PR4TXAXFABRDQCFM/",
    "sender": {
        "address": "K3IO (a) verizon.net",
        "mailman_id": "79a9b3ddaa4b44baae47f92374974ac4",
        "emails": "https://mailman.amsat.org/hyperkitty/api/sender/79a9b3ddaa4b44baae47f92374974ac4/emails/"
    },
    "sender_name": "Tom Clark, K3IO",
    "subject": "[amsat-bb] Re: SDX transponder timing delay measurements?",
    "date": "2006-09-12T19:24:48Z",
    "parent": null,
    "children": [],
    "votes": {
        "likes": 0,
        "dislikes": 0,
        "status": "neutral"
    },
    "content": "Ken wrote:\n\n>> As a design goal, it would be helpful to the \n>> OD process if the delay could be made consistent \n>> within about +/-5 micro-sec -- i.e., 1500 meters \n>> (smaller is better).  It is also important to\n>> quantify the standard deviation to that bias is \n>> since that is also factored into the OD process.\n\nLet me chime in since this is one of my specialty areas.\n\nIt has been my hope/plan that the delays will be very accurately\ncalibrated, and that we will have \"certified\" ground stations that are\nalso well calibrated. I've been pushing to have ALL local oscillators on\nEAGLE and all timing clocks (remember that the 100-200 kb/s sampling\nclock is yet one more LO in the system) derived from a single, high\nstability clock. In addition to ranging, it is my hope that we can have\nan amateur, global time synchronization capability at the usec level.\n\nWhen (occasionally) it is time to do the ranging task, it might be\nnecessary to swap in a different, optimized software into the SDX --\nthis would be my backup just in case the delay is not deterministic when\nnormal SDX is running.\n\nEven if the delays are not as accurately determined as I hope, I see no\nreason that they will not be stable over times of minutes. With this\nbeing true, then we can do very accurate DIFFERENTIAL delays using N\n\"certified\" ground stations. If you do this at ~20,000 km range with\nstations ~1 earth radii, the difference observable only suffers from a\nfactor ~3 degradation. Every ground station pair you add (the number of\npairs M increases with the number of stations N as M=(N)*(N-1)/2) gives\na statistical improvement of of sqrt(M-1); hence the geometrical loss\nfrom using a differenced observable is  easily made up on the ground.\n\n73, Tom\n\n\n\n",
    "attachments": []
}