Email Detail

HTTP 200 OK
Allow: GET, HEAD, OPTIONS
Content-Type: application/json
Vary: Accept

{
    "url": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/email/YCMH55LSLY6GCWOQKT65XAXBY64WEOQS/?format=api",
    "mailinglist": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/?format=api",
    "message_id": "[email protected]",
    "message_id_hash": "YCMH55LSLY6GCWOQKT65XAXBY64WEOQS",
    "thread": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/thread/I3GYDON3LKTKOJK7FN7DS3S3MVQQUKSD/?format=api",
    "sender": {
        "address": "karn (a) philkarn.net",
        "mailman_id": null,
        "emails": null
    },
    "sender_name": "Phil Karn",
    "subject": "[amsat-bb] Re: ARISSat telemetry and Doppler tuning",
    "date": "2011-08-19T04:01:33Z",
    "parent": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/email/JWLZOIY5K6JK6EAOCNI4IH2F6PRGVNTB/?format=api",
    "children": [
        "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/email/MXBKBUGIFNDBP653TKDBBW2BIU5USZGZ/?format=api"
    ],
    "votes": {
        "likes": 0,
        "dislikes": 0,
        "status": "neutral"
    },
    "content": "On 8/18/11 6:59 AM, Alan P. Biddle wrote:\n> Ron,\n> \n> That behavior is common around TCA, Time of Closest Approach.  At that time\n> everything is changing rapidly, and slight errors in QTH position, system\n> clock, and Keps can be magnified. \n\nAs everybody knows, even tiny errors in the Keplerian mean motion (MM)\nwill accumulate over time and put the satellite ahead of or behind where\nit really is. That will show up as a large frequency error when Doppler\nis changing rapidly at closest approach, but a small (or no) error near\nAOS and LOS when Doppler isn't changing rapidly anyway.\n\nSo instead of manually tuning the radio to compensate for unpredicted\nDoppler, why not manually tune the element set? I recommend manually\nadjusting the \"mean anomaly (MA) at epoch\" until the satellite is on\nfrequency. This parameter says where the satellite is within its orbit\nrelative to perigee at the epoch time, so changing it slides the\nsatellite forward and backward along its orbit. If this is indeed the\nmain error in the element set, then correcting it should cause the\nsatellite to track normally even through closest approach.\n\nThis has the added advantage of correcting your antenna pointing as well\nas your radio tuning.\n\nThis is probably better than tuning the mean motion (MM) as it would be\ndifficult to distinguish between the two during a single pass. The MM is\nthe time derivative of MA, so the effect on orbital position from a\ngiven change in MM depends on how long it's been since the epoch; the\nolder the eleset, the greater the resulting change in position from a\ngiven change in MM. A given change to MA always moves the satellite by\nthe same amount regardless of how long it's been since the epoch.\n\nProperly adjusting the MM separately from the MA would require careful\nDoppler measurements of a number of orbits.\n\n-Phil\n\n",
    "attachments": []
}