[amsat-bb] Re: AO-7 calibration
Bob et al. A paper, by the undersigned--of course, on the variability of the uplink/downlink frequency for AO-7 appeared in the AMSAT Journal Vol. 30, No. 3, May/June 2007 p.23 - 26. The bottom line is the LO in the spacecraft is being affected by spacecraft temperature. The spacecraft temperature is related to the amount of time the spacecraft is in shadow/sunlight. This variability probably has always been there since the day it was launched and was deemed acceptable back in 1974. The frequency variation appears in both the transponder and the 2m beacon. Up to 6-KHz of variation was observed between full sun and maximum shadow time thru the transponder while the 2m beacon variation was around 2-KHz. The fact that both varied with spacecraft temperature shows clearly it is an AO-7 contribution. A second paper concerning the solar array power actually used and analyzed the good high-speed RTTY telemetry that was transmitted by AO-7 during the March 2009 time frame, see AMSAT Journal Vol. 33, No. 1, January/February 2010, p. 4 - 15. Now that the solar array is the only power supply it is possible that voltage and current fluctuations do affect the AO-7 LO but are likely dominant around the period of entering/leaving sunlight or when transponder loads are high. When I operated AO-7 I remember many passes where the CW ops were pumping the passband which possibly caused some frequency variations, along with the FM'ing, etc. but are impossible measure or figure out. To repeat, the dominate factor in the slow frequency variation over time is spacecraft temperature. I would recommend getting the two papers from somewhere to get the full details rather than depending on the highly-condensed versions above. Best regards, Jim, N8OQ (formerly KG4QWC) ___ Sent via AMSAT-BB@amsat.org. Opinions expressed are those of the author. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
[amsat-bb] Recent AO-7 AMSAT Journal Papers
Greetings, Two recent papers concerning the historical and current behavior and operating aspects of AO-7 were written and published in the AMSAT Journal by the undersigned. I would recommend those who are interested contact the AMSAT office, Martha, and get copies of the two articles to read. "AO-7's Frequency Variability as a Proxy for Spacecraft Temperature', (2007), The AMSAT Journal, May/June 2007, pp. 23 - 26. "AO-7 - 35 Years in Space: Solar Array Power", The AMSAT Journal, January/February 2010, pp. 4 - 15. There is a wealth of information in these two articles and are good jumping off points for further study of AO-7. 73, Jim DeYoung, N8OQ (formerly KG4QWC) ___ Sent via AMSAT-BB@amsat.org. Opinions expressed are those of the author. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
[amsat-bb] ARISSat-1 (37772) decay date update for 2011 Dec 27
Greetings, The decay rate of ARISSat-1 has slowed down from the last decay prediction I produced on 2011 Dec. 14. It currently appears that ARISSat-1 (37772) will now decay on 2012 January 3 plus or minus a day. Caveat lector. Jim, N8OQ ___ Sent via AMSAT-BB@amsat.org. Opinions expressed are those of the author. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
[amsat-bb] Re: ARISSat-1 RADIOSKAF-V KEDR
Farrell, An often used rule-of-thumb in astrodynamics for "decay" height is about 140 kilometers which is about 87 miles. A satellite that gets that far into the atmosophere will burn up during it's final orbit in short order! I would recommend you just keep trying until you are sure the satellite is no longer in orbit. I will post an updated decay prediction on AMSAT-BB this afternoon for operator planning purposes. Jim, N8OQ ___ Sent via AMSAT-BB@amsat.org. Opinions expressed are those of the author. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
[amsat-bb] ARRISSat-1 (37772) decay date update for 2011 Dec 14
Greetings, It is time for another decay date prediction update. As the satellite has gotten lower the atmospheric drag has increased significantly. This prediction update uses solar data through 2011 Dec. 14. The fit only includes orbital height data between Dec. 9 and Dec. 14. The decay date now indicated is 2011 Dec. 31 with a rule-of-thumb error estimate of about +/- 3 days giving a decay date ranging between 2011 Dec 28 to 2012 Jan 3. Jim, N8OQ ___ Sent via AMSAT-BB@amsat.org. Opinions expressed are those of the author. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
[amsat-bb] ARISSat-1 (37772) decay date update for 2011 Nov. 30th
Greetings, Using solar data through 2011 Nov. 30 and updating the decay fit I am getting a re-entry date of 2012 January 12 with a rule-of-thumb error estimate of +/- 10 days or so for ARRISSat-1 (37772). Regards, Jim, N8OQ ___ Sent via AMSAT-BB@amsat.org. Opinions expressed are those of the author. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
[amsat-bb] ARISSat-1 (37772) decay
Greetings, First, thank you Mineo for reading the AMSAT Journal and making several of my papers available on your web site. My AMSAT Journal paper published in the March/April 2011 issue is actually still fairly valid for the scenarios shown in the paper. The solar flux has turned out to be somewhat higher than was used/predicted in the paper. This has caused the atmospheric densities to be higher which results in higher decay rates. When I wrote the paper I had this nagging feeling that stopping the release height scenarios at 370-km was not going to be high enough. We are very fortunate that the ISS was boosted to such a height before release of ARISSat-1 and not after release! There is a valuable lesson, I think, to be made with respect to predicting satellite decay dates far into the future. The future state of the atmosphere, i.e. the atmospheric density that the satellite will pass through is poorly predictable in the long-term, say starting greater than a week or two into the future. Predictions of satellite decay dates months in the future should be evaluated with the understanding that your date of prediction errors may be large. The errors are due to the future uncertainties of the orbital path which grow quickly with time in a prediction. The atmospheric density is not the only source of error. Your orbit model, the integrator, and the accounting of the gravitational and drag forces among others will affect your results. Predictions of satellite decay dates are not do-and-forget. The general process is to make a prediction, get new measured observations of the height in the future, and at some point re-do your prediction when the errors become significant to you. With that all said here is my current prediction using the same tools used in the AMSAT J. paper and produced as of 2011 November 13th. The decay of ARISSat-1 (37772) will happen nominally on 2012 January 30th with a 10% rule-of-thumb error allowance of 18 days around this date. The errors may be larger than the rule-of-thumb indicates! Jim, N8OQ ___ Sent via AMSAT-BB@amsat.org. Opinions expressed are those of the author. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
[amsat-bb] FO-29 off
Greetings, I just got back on the air from my new QTH (FM07uv) and monitored the beacon with good signals on Sep. 29 from 20:51 to 21:02 UTC. I heard no transponder activity and no beacon signal on the near zenith pass here on Sep. 30. from 19:51 to 20:05. Jim, N8OQ ___ Sent via AMSAT-BB@amsat.org. Opinions expressed are those of the author. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
[amsat-bb] Orbital lifetime of ARRISat-1
Greetings, If you were a member of AMSAT-NA you would receive the AMSAT Journal and could have read the article I wrote for the last issue concerning the predicted lifetime of ARRISat-1. The paper presented predictions for up to a maximum release height of 370-km and there is enough information to extrapole to the higher release height as realized. The recent reboosts put the release height somewhat higher but I would guess a lifetime of about one year. The actual Sun-state influences the atmospheric densities of the future that ARRISat-1 passes through will control the actual lifetime. Even tho I am all packed up to move to my retirement home I will write a short update to that paper using the actual release height and submit it to the Journal. I would encourage everyone (if you aren't a member already) to join AMSAT-NA and read the journal there is a lot of good stuff there. Jim, N8OQ ___ Sent via AMSAT-BB@amsat.org. Opinions expressed are those of the author. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
[amsat-bb] AO-7 telemetry request: Pre-1981 and 2009
Greetings, I am looking to obtain good quality telemetry from AO-7's 435.1-MHz RTTY telemetry event during February and March 2009. I woud appreciate receiving good quality raw RTTY telemetry. I am especially interested in the time period before 2009 March 3 and after 2009 March 6. Telemetry collected between about 0 hours UTC and 12 hours UTC would be especially useful from any of the 2009 February/March time period. Good quality telemetry is defined as being collected continuosly for at least 4 minutes during a pass. If you have already "published" your telemetry to the AMSAT-BB or to DK3WN's web blog I already have your data so there is no need to resend. Please send any unpublished RTTY telemetry here to the AMSAT-BB. If anyone has any AO-7 RTTY telemetry from the "early days", before 1981 I would really love to get that data! If you only have it in paper form or on punched cards I would like to get it. I would be glad to put it in machine readable form and return the originals and the data to you. Thank you very much for your efforts and interest. Jim, N8OQ ___ Sent via amsat...@amsat.org. Opinions expressed are those of the author. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
[amsat-bb] Another Field Day Call
Greetings, I will be the satellite station (VHF/UHF terrestrial too) for the Alexandria Radio Club (W4HFH) operating in FM and SSB modes only. It will be interesting this year since there is a big high-tension power line and substation in one quadrant, buildings in two other quadrants and high steel overpasses from I-95 in the other quadrant. I wonder if I'll be able to hear anyone? Perhaps I'll only hear my own reflected signal or maybe I can resonant all the metal around and talk down to the horizon! Nothing like a little RF anarchy while operating in harsh conditions I say! What did you say your call sign was? Which station is going to be near the center of the passband? Hi, hi!!! Jim, N8OQ ___ Sent via amsat...@amsat.org. Opinions expressed are those of the author. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
