[amsat-bb] Re: 150 cubesats to provide global WIFI multicasting
Hello everybody, I agree with Trevor, GS requirement for the 2.4 GHz band are quite challenging. Anyway, I have another question, what kind of orbit this constellation will be designed for? If it is less than 500 km, how many *months* will it last? 73s Fabio iz5xrc On Mon, Feb 10, 2014 at 8:43 PM, M5AKA m5...@yahoo.co.uk wrote: Yes, a dish needed, ISS HamTV provides a good illustration of the requirements to achieve a 2 Mbps downlink at 2400 MHz. 73 Trevor M5AKA On Monday, 10 February 2014, 18:16, Howie DeFelice howied...@hotmail.com wrote: Just in case anyone was curious about the practicality of actually transmitting WiFi from a cubesat, I did a quick link budget. Based on typical 802.11 specs, the MDS of a receiver is about -90 dBm. The path loss at 2.4GHz between a ground station and a satellite overhead in a 600Km orbit is a little over 155 dB. Assuming a zero gain antenna on the typical WiFi client radio, the required EIRP from the cubesat is in the neighborhood of 4KW. I don't think we are quite there yet with current solar cell technology not to mention the difficulty keeping the PA cool :) - Howie AB2S ___ 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 ___ 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 ___ 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: ISS HamTV Frequencies (range gain)
Hi all, 1 or 2 degree per second is an educated guess for almost all passes. If the pass is over head the speed will increase up to 4/5 degree per second (as maximum value), such a speed is not achievable by all rotators. Hope that helps, 73s Fabio IZ5XRC www.amsat.it On Mon, May 13, 2013 at 2:52 PM, Robert Bruninga bruni...@usna.edu wrote: One needs to also realize duration. The time say above 70 degree elevation (where rates are highest) are less than 2% of the total pass times. Not worth worrying about. Similarly, a LEO satellite spends 70% of its time below about 22 degrees. (but it is far away and needs max gain). So simply design for the best operation for most of the time when the link will work. Remember, the satellite is 3000 km away on the horizon and very weak, but as it gets into say 1500 km it is twice as close and 4 times (6 dB) stonger which is a heck of a lot of gain. When it goes directly overhead it is another 6 dB closer which is more than *ten* times the signal on the horizon, so don't worry about the 2% of the time it is going to be above 70 degrees. The signa is 10 times stronger and easy to deal with. Bob, WB4APR -Original Message- From: amsat-bb-boun...@amsat.org [mailto:amsat-bb-boun...@amsat.org] On Behalf Of Art McBride Sent: Monday, May 13, 2013 12:44 AM To: 'Roger'; amsat-bb@amsat.org Subject: [amsat-bb] Re: ISS HamTV Frequencies Roger, A SWAG, (Wild Guess) 1 degree per second at a Zenith of 90 degrees. Anything less than 90 degrees will be slower with several minutes spent near the horizon. You can use an orbital program to get exact numbers. With a wide beam width antenna, the lag overhead may never require the antenna to move with the object, as there will be time for the antenna system to catch up after passing overhead. Art, KC6UQH -Original Message- From: amsat-bb-boun...@amsat.org [mailto:amsat-bb-boun...@amsat.org] On Behalf Of Roger Sent: Sunday, May 12, 2013 2:34 PM To: amsat-bb@amsat.org Subject: [amsat-bb] Re: ISS HamTV Frequencies Anybody off the top of their heads know how many degrees a second swing are (is?) required for direct aim at the ISS? I know there are beam width tolerances, altitude variations and degree above horizon variations but I'm looking at Bob B's fixed antenna aiming of 15-20 degrees above horizon to evaluate swinging a dish without torque eating up the drive train... Roger WA1KAT On 5/12/2013 5:01 PM, M5AKA wrote: The AMSAT-UK page at http://amsat-uk.org/2013/05/12/hamtv-from-the-iss/ provides the links, they are: Facebook https://www.facebook.com/Hamtvproject More information at http://www.amsat.it/Amsat-Italia_HamTV_brochure.pdf and http://www.amsat.it/Amsat-Italia_HamTV.pdf The HamTV.pdf gives the link budget, looks like there's 7dB of coax/connector losses to overcome between the ISS transmitter and the antenna. That document indicates a 90cm dish should be sufficient. I believe that it's going up on ATV 4 which is currently slated for June 5. 73 Trevor M5AKA ___ 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 ___ 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 ___ 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 ___ 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: Newsky dongle
Hello everybody, I'm using SDR# (v.999) with several dongles (FCD, FC0013, E4000) and it works great. I could suggest to use a notch filter (it could be a quarter wave stub) to limit front-end overload from FM broadcasting. Hope that helps, 73s Fabio iz5xrc On Tue, Jan 15, 2013 at 8:47 PM, Mark Spencer wa8...@comcast.net wrote: Scott, I too have just started playing with the NooElec SDR. One thing that hit me between the eyes is that the SDR is not very sensitive. I have had moderate success copying local two meter traffic and APRS signals on 144.390 by using a broad band preamp at the radio and also one at the antenna, with that arrangement the SDR hears much better. 73, Mark Mark Spencer, WA8SME Education and Technology Program Director ARRL, the national association for Amateur RadioTM 43 Pinelock Dr. Gales Ferry, CT 06335 860-381-5335 860-460-1139 (cell) mspen...@arrl.org ___ 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 ___ 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: ISS Height Profiles @ Heavens-Above.com
Thanks Robert! Clear now. 73s Fabio iw8qku/5 On Fri, Jan 13, 2012 at 4:59 PM, Robert McGwier rwmcgw...@gmail.com wrote: These maneuvers are not done continuously around the orbit. They are typically done in burns done at apogee and perigee if all they are doing is raising/lowering the orbit and minimizing any changes to the orbital plane. Think of it like this. When I turn the propulsion on, I do not change my CURRENT instantaneous position while I am burning. What I change is my velocity. So if I burn the motor at apogee and the motor is firing along my velocity vector, then I am speeding myself up. THIS RAISES PERIGEE because I will have the same height but my speed will cause the position on the OTHER SIDE of the orbit to be raised. Similarly, I slow down at apogee, perigee is lowered. If I speed up at perigee, apogee is raised, Did this help? Bob On Fri, Jan 13, 2012 at 10:28 AM, Fabio Azzarello iw8...@amsat.orgwrote: Hello everybody, ISS heights plots are available at the following link: http://www.heavens-above.com/OrbitHeight.aspx?satid=25544startMJD=55610lat=43lng=11 I've noticed that Apogee and Perigee heights have different behaviour during reboosts (look at mid September for example), could anybody help me to understand why? Thanks in advance, 73s Fabio iw8qku/5 ___ 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 -- Bob McGwier Facebook: N4HYBob ARS: N4HY ___ 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 (37772) decay
Hello Everybody, I totally agree with you James... the process is a continuous evolution. I did my prediction on October 6th for the Chicken Little Competition and my date was January 23rd 2012. It surprisingly agrees with your prediction done almost one month later, this make me think that my assumptions were right, up to now at least. 73s Fabio IW8QKU/5 Hi Jim, Thanks for the update on your AMSAT Journal article. There are several people on the bb who are following this topic and are busy plotting data. Any futher thoughts you have, as we move towards January would, I am sure be of interest. 73 John G7HIA From: DeYoung James deyoung_ja...@yahoo.com To: amsat-bb amsat-bb@amsat.org Sent: Tuesday, 15 November, 2011 17:29:31 Subject: [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 ___ 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 Re-entry Prediction
Hello everybody, I did my guess before the end of the Chicken Little Competition... maybe a little too early to catch the correct date of re-entry. Anyway, I've noticed that your prediction, Mineo, seems to be optimistic towards the date of re-entry. I think that, close to that date, sat's height will decrease much faster than you've predicted thus the re-entry could be sooner than April 9th. I will be pleased to share my prediction with anybody is interested. 73s Fabio IW8QKU/5 Thanks, Mineo. Your work is interesting. If my memory is correct, the prediction shared at the AMSAT Symposium is for April 2012. Your results agree! 73, Mark N8MH At 11:13 AM 11/12/2011 +0900, Mineo Wakita wrote: I calculated and predicted the time of ARISSat-1 Re-entry. http://www.ne.jp/asahi/hamradio/je9pel/arissat5.htm JE9PEL, Mineo Wakita ___ 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 ___ 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: Response to my request of information about EduSatfrom GAUSS team in Rome: Re: [CubeSat] Edusat operative or failure
Hello, just to add a bit of information... can refer to the following links: https://apps.fcc.gov/els/GetAtt.html?id=112305 http://www.imtsrl.it/s_band.html Hope this helps, 73s Fabio IW8QKU/5 ___ 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 battery
Hi all, what about the following link? http://www.nrel.gov/features/20100708_battery.html 73s Fabio IW8QKU/5 *Subject: [amsat-bb] ARISSat-1 battery From: g0mrf@xxx Date: Mon, 29 Aug 2011 08:50:45 -0400 (EDT) Hi all. The ARISSat team seem to have reached the conclusion that the Silver Zinc battery technology is not really suited for an orbiting satellite with a 55 / 35 minute charge and discharge cycle. I wonder if a couple of small Lithium polymer battery packs would be a suitable replacement for ARISSat-2 ? I note that there are safety issues with Li-ion technology, but there are some small battery packs of 10Whr / 20Whr 30Whr modules which have NASA approval for manned space flight. From the odd snippet of information on the power required during eclipse (is it 7 Watts for 35 minutes) it looks like 20-25% depth of discharge for the 20Whr battery pack. That's probably OK for a 9 month mission ?? Thanks David G0MRF http://www.clyde-space.com/documents/1902* ___ 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 battery
Hi, here is another interesting link: http://www.nrel.gov/vehiclesandfuels/energystorage/news/2011/1482.html could it be an interesting opportunity for our birds ? 73s Fabio IW8QKU/5 On Mon, Aug 29, 2011 at 3:09 PM, Fabio Azzarello iw8...@amsat.org wrote: Hi all, what about the following link? http://www.nrel.gov/features/20100708_battery.html 73s Fabio IW8QKU/5 *Subject: [amsat-bb] ARISSat-1 battery From: g0mrf@xxx Date: Mon, 29 Aug 2011 08:50:45 -0400 (EDT) Hi all. The ARISSat team seem to have reached the conclusion that the Silver Zinc battery technology is not really suited for an orbiting satellite with a 55 / 35 minute charge and discharge cycle. I wonder if a couple of small Lithium polymer battery packs would be a suitable replacement for ARISSat-2 ? I note that there are safety issues with Li-ion technology, but there are some small battery packs of 10Whr / 20Whr 30Whr modules which have NASA approval for manned space flight. From the odd snippet of information on the power required during eclipse (is it 7 Watts for 35 minutes) it looks like 20-25% depth of discharge for the 20Whr battery pack. That's probably OK for a 9 month mission ?? Thanks David G0MRF http://www.clyde-space.com/documents/1902* ___ 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: EVA 29 live stream coverage
Hello, Nasa TV Schedule reports: *August 3, Wednesday 10 a.m. - ISS Expedition 28 Russian Spacewalk Coverage (spacewalk begins 10:30 a.m. EDT.)* it seems that the deployment of ARISSat/KEDR will be one of the first tasks of the EVA, does anybody know where to find the EVA timeline? 73s Fabio Azzarello IW8QKU/5 ___ 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: PREDICT for 64-bit Winderz?
Hello, I would suggest to use DOSBOX, it works fine on many OS. Don't know if it works properly also on 64bit WIN, but it is worth a try at least. RGs Fabio Azzarello IW8QKU ___ 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
