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{
    "url": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/email/C63KI26YJTVJONZWJXW45M2AALBCEKCY/?format=api",
    "mailinglist": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/?format=api",
    "message_id": "[email protected]",
    "message_id_hash": "C63KI26YJTVJONZWJXW45M2AALBCEKCY",
    "thread": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/thread/C63KI26YJTVJONZWJXW45M2AALBCEKCY/?format=api",
    "sender": {
        "address": "N2OEQ (a) aceweb.com",
        "mailman_id": "e63b1ea442884559874553314efaac46",
        "emails": "https://mailman.amsat.org/hyperkitty/api/sender/e63b1ea442884559874553314efaac46/emails/?format=api"
    },
    "sender_name": "Patrick McGrane",
    "subject": "[amsat-bb]  Future radical satellite designs",
    "date": "2007-07-08T04:50:06Z",
    "parent": null,
    "children": [
        "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/email/2VZH7WBK2LY56EQH4PYYMIEHVGHF5QUD/?format=api",
        "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/email/HTLRTGE4HRL5VYKSDCRJWMHPNNBLXCKH/?format=api"
    ],
    "votes": {
        "likes": 0,
        "dislikes": 0,
        "status": "neutral"
    },
    "content": "\nGreetings from Patrick N2OEQ\n\nLet me preface my comments by stating the following;\n\nThe solar energy in space, outside the atmosphere, is approximately 1400 watts per square meter.\nThis equates to about 130 watts per square foot. AO-51 ( amsat Echo ) is roughly a one foot cube \ncovered with 27 percent efficient GaAs solar cells which cost approximately 20,000 dollars. With \nthat efficiency and almost complete side coverage with solar cells, I would guess the satellite \nsolar cell power conversion is about 25 to 30 watts for half the orbit time. Conservatively, that \nis about 300 watthours or more per day. Now, the transmitter might use 2 watts of energy to provide \nthe 500 milliwatt downlink RF power and the satellite control electronics uses about 1 watt of \nenergy. The Digital transmitter might use another couple of watts. For argument sake, I'll say the \nsatellite uses 5 watts continuously for 24 hours per day or about 125 watthours per day. For some \nreason, it seems the full potential of the solar cells is lost or underutilized.\nThe transmitters power is kept low to reduce the batteries depth of discharge to a minimum to \nextend the battery life.\n\nThe point I am trying to make is that if amsat is going to pioneer new technologies in satellite \ndesign, they should keep their eye on the big picture or the basics of operation. I'm aware that \npeople are trying to find a replacement for batteries but I would go further in saying that perhaps \nfor future designs that amsat resort to solar dependant power output or specifically, full \ntransmitter power directly powered by the solar cells and a sleep mode while the satellite is in \ndarkness.\n\n>From what I have learned about satellites, batteries are the weakest link often spelling disaster \nand limited satellite lifetimes. I would rather enjoy a high power intermittent solar satellite for \nmany years more than the average lifespan of one dependant on battery life and cycling.\n\nSome will argue that they want continuous duty whenever the satellite is in range, day or night.\nI would like to see a longer lived satellite capable of full power half the time that could \npotentially last several decades in orbit.\n\nAnother point to ponder is the idea of asking to have auxilliary or piggyback payloads on larger \ncommercial satellites. This was done with the russian RS satellites and more recently with India's \nHamsat. The larger commercial satellites would probably have much larger and more efficient power \nbudgets. I just read on the space.com website ( linked from amsat ) that the new Directv satellite \nis about 6 or 7 thousand pounds and probably utilizes the most advanced and reliable technology \navailable. Wouldnt it be cheaper and easier to build an auxilliary payload versus an autonomous \nsatellite? This question has probably been answered many times but I'll bring it up again.\nIf it is a costly idea, is the additional cost justified by better, more reliable operation?\n\nThanks for allowing this forum and thanks for all replies.\n\n73, patrick\n\n\n",
    "attachments": []
}