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{
    "url": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/email/NMBBUKQP23DBOQH7O5Q7WT2T2TO5WISZ/",
    "mailinglist": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/",
    "message_id": "[email protected]",
    "message_id_hash": "NMBBUKQP23DBOQH7O5Q7WT2T2TO5WISZ",
    "thread": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/thread/NMBBUKQP23DBOQH7O5Q7WT2T2TO5WISZ/",
    "sender": {
        "address": "clivew (a) zetnet.co.uk",
        "mailman_id": null,
        "emails": null
    },
    "sender_name": "Clive Wallis",
    "subject": "[amsat-bb]  Recollections of OSCAR-9 & Salyut Decay Competitions",
    "date": "2008-01-11T12:08:29Z",
    "parent": null,
    "children": [
        "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/email/QL6J2E4S7ULFJTWNZ4A3AB7XM5LW33RC/"
    ],
    "votes": {
        "likes": 0,
        "dislikes": 0,
        "status": "neutral"
    },
    "content": "Hi,\n\nHere is some information about the OSCAR-9 & Salyut-7 decay competitions.\nI've compiled this from OSCAR News (the magazine of AMSAT-UK), and from my\nown records and memory.  I would be most interested in any additional\ninformation about these activities, which may have been remembered or\npublished.\n\nThe decay competition was first suggested by Craig Underwood, G1WTW of\nthe University of Surrey (UoS), in February 1989. In a text bulletin\nbroadcast on OSCAR-11, he anounced the rules of the competition which was\nto predict the day on which UoSat-1 will decay completely. the entry to be\nsent at least one month before the prediction.  The prize for the winning\nentry was a UoSAT sweatshirt.  Craig also posted a table of satellite\nheight and mean motion, showing the orbital decay between mid 1988 and end\nof January 1989.\n\nThe task of running the competition was then passed to  AMSAT-UK, who\nadded additional prizes, any item of AMSAT software and two AMSAT-UK T\nshirts.  Five entries were allowed per person, to be precicted one  month\nbefore the event.\n\nOSCAR-9 decayed at 07:51:49 UTC on Friday 13 October 1989.  The results of\nthe competition were anounced by Ron G3AAJ on the AMSAT-UK eighty metre\nnet the following Sunday.  The winner was Geoff Roberts G3ENY (15\nOctober). My entry was second or second equals (October 11), Unfortunately\nI can't remember the other runners up.\n\nIn his monthly news bulletin, broadcast at the end of October, Richard\nG3RWL reported -\n\n\"Max White at the Royal Greenwich Observatory reports that UoSAT-OSCAR-9\n(UoSAT-1) decayed on Friday 13th October at 0751.49 GMT on Rev 44761.\n\nTwo possible locations for the final decay are given by different agencies:\n49.2S 220.9E and 46.4S 220.0E\n\nThese locations are over the South Pacific and were probably out of range of\nany receiving stations. The last report of telemetry we have so far is from\nK9CIS at the Richmond Community College in the USA. They heard the satellite\nbetween 03:43 and 03:49 on 13th October, and reported good signal strength and\nnominal telemetry. Any telemetry or reports from the last 6 hours of UO-9's\nlife would be appreciated by the UoS.\"\n\nThe following announcement appeared in the news bulletin on OSCAR-11 -\n\n\"UoSAT-1 decayed on 131089 at 0751.49 GMT on Rev 44761 around 49.2S 220.9E\nand 46.4S 220.0E.  Any telemetry or reports from the last 6 hours of\nUO-9's life would be appreciated by UoS - thanks to all those who have\nalready submitted reports.\"\n\nThe winner of the competition was also mentioned in the next OSCAR News,\nDecember 1989, but no mention of the runners up!  I never received a prize,\n(I didn't like to ask!).\n\nInterestingly, there was also an item in the same issue of Oscar News from\n'The Westlink Report' saying that UO-9 was last heard on 435.025 MHz. by\nZS6CCD at 12:00 UTC.\n\nI last heard OSCAR-9 on 12 October at 20:31 UTC (TCA) transmitting\ntelemetry & WOD.  Here is one of the last frames I received -\n\n\nUOSAT-1           8910120203424 COMPUTER GENERATED TELEMETRY\n00100101020302645503000304000405591806275607397A08450909557E\n10100011010112000313000214024315832D163545176303184508195418\n20150621020122615223000124009F25412026425727334128450B295608\n30000331020032666733244234011735306336354737392C38457D39541A\n40110441080D42743643000744140545001046003147447448463D494898\n50110551080C52272053156454463055361456444757447558461E59471E\n\nExamination of this telemetry, shows that the 435 MHz. beacon is OFF.\n\nThere had been some interest in the decay of OSCAT-9's orbit well before\nthe competition was suggested.  At the 1987 AMSAT-UK Colloquium, Peter\nCleal G8AFN presented a paper describing factors affecting the decay of the\nsatellite. He queried why the satellite was still in orbit when the\nexpected orbital life was five years from 1981, and why the orbital\ncalendars for UO-9 were often incorrect.  Peter precicted that the\nsatellite would decay in March 1990, plus or minus three months.  Excellent\nfor such a long term prediction.  This paper was published in OSCAR News\nApril 1988. There were no Colloquium proceedings in those days.\n\nAt the 1989 AMSAT-UK Data Space Collloquium, Peter presented another paper\ndetailing how he related the decay of the satellite to variations in solar\nactivity and other factors.\n\nGeoff G3ENY was a worthy winner of the competition, as his entry dated 30\nJune was published in August's OSCAR News.  It showed graph of height\nagainst time.  His predictions (all guesses he said) varied from 06 August\nto 10 November, with the winning entry 15 October nicely in the middle of\nthe range.  Geoff also wrote two articles in OSCAR News about solar\nactivity, and mentioned that a burst of solar activity in March had\ndoubled the rate of UO-9's decay.\n\nRegarding my own predictions, after some initial unsuccessful attempts at\ncurve fitting, I decided a scientific approach was needed.  The\ndensity of the exosphere appeared to be the most likely factor determining\nthe rate of decay, which could be integrated to give change in height. The\ndensity is a function of height and exospheric temperature, and was\ndetermined by using a simple look-up table.  The temperature was determined\nby solar radiation, and some periodic time related factors.\n\nThe method I used was to statistically analyse the historic data. This\nproduced results which were then used with solar predictions, to do a day\nby day calculation of decay rate & height until the critical re-entry\nheight was reached. I used a floppy disk based BBC-B Micro computer\nprogrammed in BASIC, for all the calculations.\n\nMy source of the daily 10.7GHz. solar information was the weekly printed\nbulletins from the U.S Solar Observation Centre at Boulder, Colorado.\nThe values of 3-monthly flux were obtained from tables published in\nthe Wireless Engineer magazine.  Those were the days before the Internet!\n\nThe method only yielded partial success, and I tended to get different\nresults every time the software was run.  My five predictions dated\nbetween 27 August and 10 September, were October 11, 17, 20. 24 & 31\n\nOne problem in 1989 was getting Keplerian elements. AMSAT-UK usually\ndownloaded them from a bulletin board in North America via an expensive\ntransalantic telephone call. These were then read out on the AMSAT-UK 80\nmetre net. Often there was a burst of interference just as the vital mean\nmotion was being read out!  Keplers were also available on the packet radio\nsystem and on OSCAR-11. Peter G8AFN and I often used to meet at Stevenage\nrailway station, where we changed trains on our way to work, in the mornings.\nWe exchanged the latest Keplers, and details of our observations.\n\nTo obtain updated values of mean motion I developed a method of using the\nobserved values of the time of closest approach (TCA), ie zero Doppler. The\nerror between actual TCA and predicted TCA could then be used to correct the\nmean motion. Thus daily values of mean motion and decay rate were\ncalculated.\n\nOne interesting outcome of this study was that I found that the measured\ndecay rate was usually twice the 'Drag' value in the Keplerian elements.\nThe units of drag are often wrongly described as revs/day/day.  They should\nbe double-revs/day/day.  This may have accounted for errors in the orbital\ncalandar for OSCAR-9.\n\nThe Salyut-7 decay competition was organised by Pat Gowen G3IOR and\nAMSAT-UK. Details were published in OSCAR News December 1990. The time and\ndate of re-entry was required, which had to be received at least one week\nbefore the event. Three entries were allowed. The prize was a handsome set\nof commemorative Soviet space stamps.\n\nSalyut-7 crashed to earth in Chile at 03:44 UTC on 07 February 1991.\nDetails were published on the amateur packet/satellite network and in OSCAR\nNews April 1991. There were over 100 entries, from all over the world.  The\nwinner of the competition was Mike Billow N1BEE, who predicted 03:30, just\n17 minutes early.  Second was Hazel, XYL of G3FMQ at 04:19.  I came third\nat 08:24.  Other close contenders included LA4XC, G4ODC, G4BDW, W3/G3ZCZ,\nG3LDI, G3FMQ, G4CUO, G4FKC, PA0DLO, G0BAF, G4ULS, VE3EFX and WB6LLO, who\nall came up with predictions superior to the estimates produced by the\nprofessional agencies.\n\nI received a magnificient certificate, designed and hand painted by Norma,\nG3IOR's XYL. Duplicates of the space stamps were also included.\n\nA similar method was used for the calculations, which used files of mean\nmotion, solar flux, and historic three month solar flux data.\n\nTrust this is of interest, and looking forward to any comments.\n \n73     \n\n\t Clive    G3CWV\n\n         Hitchin, North Hertfordshire, UK.\n",
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}