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{
    "url": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/email/DY2BXH2D2G2Q7YSMYTF6RY6F5VISAZZ2/?format=api",
    "mailinglist": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/?format=api",
    "message_id": "[email protected]",
    "message_id_hash": "DY2BXH2D2G2Q7YSMYTF6RY6F5VISAZZ2",
    "thread": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/thread/DY2BXH2D2G2Q7YSMYTF6RY6F5VISAZZ2/?format=api",
    "sender": {
        "address": "tom.k3io (a) gmail.com",
        "mailman_id": "a3cf919d50e34818957525c30686cb1e",
        "emails": "https://mailman.amsat.org/hyperkitty/api/sender/a3cf919d50e34818957525c30686cb1e/emails/?format=api"
    },
    "sender_name": "Tom Clark, K3IO",
    "subject": "[amsat-bb] Re: AO-51 magnet reversal tonight",
    "date": "2009-12-03T08:48:08Z",
    "parent": null,
    "children": [
        "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/email/WEXP6EWVKJWVR3HMWGK532PCHNWJGTOM/?format=api"
    ],
    "votes": {
        "likes": 0,
        "dislikes": 0,
        "status": "neutral"
    },
    "content": "Drew posted\n>  On the 2242UTC pass of AO-51 tonight, we will try for the first time to\n>  reverse the magnet and \"flip\" the orientation of the satellite. While we\n>  do this, the 435.300 transmitter will be shut off for about 10 minutes.\n>  If the reversal is successful, we should see some changes in signal\n>  levels and patterns. This particular maneuver has not attempted since\n>  launch.\n>\n>  I'd appreciate any signal reports or observations from this evening and\n>  the next few days be emailed to [email protected]  or [email protected].\n\n\nI'm really glad we are finally testing this AO-51 experiment! Thanks for\nlistening to my request. I'm most interested in seeing the results of this test,\nbut I don't see the ao51-modes reports, so please keep me posted offline.\n\nSince angular momentum must be conserved when you \"flip\" the s/c. The s/c body\nshould precess (probably looking like tumbling) until the momentum dampers\nabsorb the change. Keep an eye on the solar panel currents and I'll bet the spin\nrate will change.\n\nConcerning your other note:\n>  In related news, as the spacecraft spin inexplicably continues to slow,\n>  we are seeing increasingly larger dips in the spacecraft voltage when\n>  the panels are poorly aligned to the sun.\n\nMy guess is that the momentum loss is due to eddy currents induced in the s/c\nbody by the earth's magnetic field. Sometime drop a piece of (non-magnetic)\naluminum into the poles of a big magnet -- you'll see the aluminum change speed\nnoticeably. Back in the antique days of mechanical speedometers in cars, the\nspeedo cable turned a permanent magnet above an aluminum or brass disk connected\nto the indicator. As the magnet spun faster, eddy currents would drag the\ndisk/pointer to higher values.\n\nThere are some good treatments of eddy currents&  angular moment on YouTube at\n\n    http://www.youtube.com/watch?v=39r8moW_p-w ,\n    http://www.youtube.com/watch?v=WZ-3pxKdT8Q ,\n    http://www.youtube.com/watch?v=jmfKmUq2EI8&feature=related ,\n    http://www.youtube.com/watch?v=H3xqH1arESA&NR=1 and\n    http://www.youtube.com/watch?v=brNBVDCeECg&feature=related .\n\nIn these clips, note that moving brass or aluminum items (acting just like the\nsatellite body) \"feel\" the  static magnetic (like the earth's magnetic field).\nFor some (boring) physics theory, follow the links at\n      http://en.wikipedia.org/wiki/Eddy_current.\n\n73 de Tom, K3IO\n\n",
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}