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{
    "url": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/email/7MPSXLHN5JGX2KCCP7SS4OLWG6NGNAO6/",
    "mailinglist": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/",
    "message_id": "[email protected]",
    "message_id_hash": "7MPSXLHN5JGX2KCCP7SS4OLWG6NGNAO6",
    "thread": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/thread/7MPSXLHN5JGX2KCCP7SS4OLWG6NGNAO6/",
    "sender": {
        "address": "rjc53 (a) cornell.edu",
        "mailman_id": null,
        "emails": null
    },
    "sender_name": "Robert Christ",
    "subject": "[amsat-bb] Re: Since there's been a lot of ISS chatter recently,\tI \tthought this might be a good time to post",
    "date": "2010-07-14T20:44:10Z",
    "parent": null,
    "children": [],
    "votes": {
        "likes": 0,
        "dislikes": 0,
        "status": "neutral"
    },
    "content": "My original back of the napkin calculations showed a 6-8' dish, so\nyes, this seems\napproximately correct.  Point to keep in mind: the 10 dBm will not be\nthe Tx power.  10 dBm will be the maximum Tx power.  Due to bad\norientation, we expect to only receive a fraction of that, unless\nsomeone gets particularly lucky with ISS orientation.  I'll be\nsimulating exactly how much\nof a fraction over the next few days, and of course could do so for anyone's\nparticular location.\nRobert\n\nOn Wed, Jul 14, 2010 at 4:32 PM, Edward R Cole <[email protected]> wrote:\n> Here is what I calculate:\n> 10 dBm  Tx power\n> 0 dBic    zero gain Tx antenna\n> 20 dBic   Rx antenna gain\n> 0 dB       Cross polarity loss\n> 902 MHz\n> 0.001 millions of km (1000km)\n> 20 K       sky temp\n> 40 K       Rx antenna temp\n> 36 K       receiver noise temp\n> 200000 Hz   bandwidth\n>\n> 151.5 dB     space loss at 1000km\n> -121.5 dBm  received signal level\n> 96 K           total receive system noise temp\n> -125.8 dBm   EIRP\n> 4.3 dB         S/N\n>\n> this was calculated using the spreadsheet I made for determining the signal\n> from MRO:\n> http://www.kl7uw.com/raseti.htm\n> click on the word \"calculate\" to download the spreadsheet.\n> this works for determining any spacecraft signal reception.\n>\n> A 20-db antenna will have around a 10 degree beamwidth so much easier to\n> point than what hams used for AO-40 on 2.4 GHz\n>\n> probably a 4 to 6 foot dish will suffice.\n>\n>\n>\n> At 08:40 AM 7/14/2010, Robert Christ wrote:\n>>\n>> Hey everyone.  I'm a researcher at Cornell, and this fall, our\n>> experimental, 1 inch diameter, “chip satellites† are scheduled to be\n>> launched on the final space shuttle flight, STS-134.  They're going to be\n>> mounted on the exterior of the ISS structure, and will be set to transmit\n>> a 902 MHz signal.  Unfortunately, we do not yet have an antenna for\n>> receiving this transmission.  After talking with Bob - Wb4APR for a while,\n>> it was suggested that the fine members of the AMSAT ­ BB might be able to\n>> helpp us. What we’re looking for is a digital capture of this 902MHz\n>> frequency (with a bandwidth of about 200KHz), during at least one ISS pass\n>> (only a few gigs of data, we believe).  No decommutation or other analysis\n>> of the signal will be required, but actually capturing the signal will\n>> require at least a 20 dbB gain receive antenna (more details in a minute).\n>> If any of you can help us in this experiment, or are able to successfully\n>> capture the signal, not only would we be incredibly grateful, but we would\n>> also be prepared to add your names and contributions to all of the published\n>> papers that will result from this mission.  It goes without saying, though,\n>> that we’d also be entirely open to suggestions if the community, or a\n>> member, were aware of some manner by which Cornell might be able to better\n>> avail itself to the both those who help us on this project and the community\n>> as a whole. So here are the technical details.  There are 3 transmitting\n>> antennas, all tiny, center-fed dipoles: two of them use wires separated by\n>> 180 degrees, and one has wires separated by 90 degrees.  Each of these\n>> dipoles is mounted a few mm from large metal panels on the ISS.  The\n>> ChipSats will transmit for approximately 10ms every 1-2 seconds, but the\n>> signal is going to be beneath the noise floor.  Detecting the signal\n>> requires a pseudorandom noise (PRN) code, which Cornell will handle once the\n>> dataset is in hand.  Since we can/will take care of the post processing,\n>> and capture isn’t guaranteed on every ISS pass (attitude alignment\n>> problems still TBD) so anyone who can take a recording of this frequency at\n>> this bandwidth for us, of any ISS pass, would be incredibly helpful. The\n>> good news is that the chips will be live and transmitting almost immediately\n>> after they are installed from STS-134, and they will transmit continuously\n>> whenever the ISS is in sunlight.  Additionally, should they survive in\n>> their environment, they are set to transmit for up to two years, which\n>> should give us many chances to receive the data and confirm that the\n>> ChipSats are functioning. Thanks for your time, everyone, Robert Christ\n>> http://www.spacecraftresearch.com/ P.S. a little extra information:  Our\n>> website is http://www.spacecraftresearch.com/projects.html if you're\n>> interested. This mission isn't explicitly mentioned there yet, but is rather\n>> a proof of feasibility study for most of the projects listed on that site.\n>>  Ah and lastly, the ERP of the transmitter is expected to be ~10 dBm, though\n>> it will almost certainly be facing in a poor orientation, giving us only a\n>> fraction of that power.  We won't know the exact amount for a few more days.\n>>  Thanks all! _______________________________________________ Sent via\n>> [email protected]. Opinions expressed are those of the author. Not an\n>> AMSAT-NA member? Join now to support the amateur satellite program!\n>> Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb\n>\n>\n> 73, Ed - KL7UW, WD2XSH/45\n> ======================================\n> BP40IQ   500 KHz - 10-GHz   www.kl7uw.com\n> EME: 144-QRT*, 432-100w, 1296-QRT*, 3400-fall 2010\n> DUBUS Magazine USA Rep [email protected]\n> ======================================\n> *temp\n>\n\n",
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}