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{
    "url": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/email/HXANDUPKSAQUKB25TNG2N2EDTXREITYD/?format=api",
    "mailinglist": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/?format=api",
    "message_id": "[email protected]",
    "message_id_hash": "HXANDUPKSAQUKB25TNG2N2EDTXREITYD",
    "thread": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/thread/HXANDUPKSAQUKB25TNG2N2EDTXREITYD/?format=api",
    "sender": {
        "address": "zleffke (a) vt.edu",
        "mailman_id": "57a24afb1cf641f98121841e6753c12e",
        "emails": "https://mailman.amsat.org/hyperkitty/api/sender/57a24afb1cf641f98121841e6753c12e/emails/?format=api"
    },
    "sender_name": "Zach Leffke",
    "subject": "[amsat-bb] FO-29 and AO-73 Antenna Patterns and Crosslinks",
    "date": "2015-10-20T15:58:24Z",
    "parent": null,
    "children": [],
    "votes": {
        "likes": 0,
        "dislikes": 0,
        "status": "neutral"
    },
    "content": "Hello!,\n     First off, I'd like to say I had a blast at the 2015 AMSAT \nSymposium.  It was a lot of fun and I know that the rest of the VT team \nreally appreciated the warm welcome from everyone.\n\nDrew and I got to talking at one point after the Banquet and he \nre-kindled an interest in something for me.  He posted a while back \nabout how the downlink for AO-73 is in the passband of FO-29's uplink, \nand that the PSK can be heard at times when monitoring FO-29's \ndownlink.  I'd like to do a bit more analysis using STK to predict when \nan 'accidental crosslink' might occur allowing a telemetry decode of \nAO-73 via FO-29.\n\nRight now I'm using a simple model for all of this where I'm treating \neach satellite as a single point in the sky.  The first question I'm \nasking (via STK simulation profiles) is when can the two \"points in the \nsky\" see each other when not blocked by the curvature of the earth.  The \nnext question I will ask of the great and glorious STK is when can the \ntwo \"points in the sky\" see each other AND when can the point in the sky \nthat is FO-29 see the point on the ground that is the VT Ground Station.\n\nWhen the second question yields accesses in time when the two spacecraft \ncan see each other and FO-29 can see the VTGS, then I have a window to \nschedule the VTGS for this experiment.\n\nThe next trick will be accounting for doppler between the two spacecraft \n(via range rate info from STK for the two points) to determine where \nexactly in FO-29's uplink passband the AO-73 signal will fall.  Then \naccount for the Linear inverting transponder offsets, then account for \ndoppler between FO-29 and VTGS.  Also, the signal spectrum will be \ninverted due to the transponder, but we can \"re-invert\" in our GNU-Radio \nflowgraph to account for that.\n\nEnd result should be an access window at VTGS along with a predicted \ndoppler curve for tuning at VTGS, ultimately getting us to an AO-73 tlm \ndecode via FO-29.\n\nMy question for the group concerns the antenna patterns for FO-29 and \nAO-73.  I'm trying to plan ahead for refining the access windows for \nwhen to actually conduct this experiment by doing a bit more than treat \neach satellite as a \"point in the sky.\"  Does anyone have any info on \nthe actual antenna pattern for FO-29?  Along with this, I remember \nreading somewhere that FO-29 has an attitude control system.  Is this \nsystem still operational and if so, what is the \"target attitude.\"  I'm \ntrying to get a sense of the antenna patterns for the two spacecraft and \ntheir orientations to identify \"sweet spots\" where antenna patterns \nmight align positively.  On the other hand it will be good to know when \nwe have an access window but one of the spacecraft is in the null of the \nantenna pattern of the other spacecraft.  For AO-73 I'm assuming simple \nwhip antennas.  I know it doesn't have a positive attitude control \nsystem, but if memory serves I think it has a bar magnet and the spin \nfrom the anodized bars imparted on it that should give me a sense of its \norientation at particular times.\n\n\nThanks in advance!\n-Zach, KJ4QLP\n\n-- \nResearch Associate\nTed & Karyn Hume Center for National Security & Technology\nVirginia Polytechnic Institute & State University\nWork Phone: 540-231-4174\nCell Phone: 540-808-6305\n\n",
    "attachments": []
}